WiredTiger Change Log

Ticket reference tags refer to tickets in the MongoDB JIRA tracking system: https://jira.mongodb.org

WiredTiger release 10.0.0, 2021-04-12

See the upgrading documentation for details of API and behavior changes.

Significant changes:

• WT-4008 Add ARM NEON support for row search operations
• WT-5083 Add mips64el support
• WT-6598 Add new API allowing changing dhandle hash bucket size
• WT-4427 Make WiredTiger timestamps always on and 8 bytes
• WT-4642 Store transaction IDs durably
• WT-5225 Create persistent file for History store
• WT-5500 Implement new history store format
• WT-6677 Map read committed/uncommitted isolation to read-only transaction
• WT-6710 Change default transaction isolation to snapshot
• WT-4833 Drop support for Python2
• WT-6410 Remove WT_SESSION.rebalance
• WT-6528 Remove offensive terminology in WiredTiger API and source code
• WT-6674 Remove Async API code and documentation
• WT-6675 Remove WiredTiger Java language API and documentation
• WT-6678 Remove Huffman Encoding support for Keys
• WT-6713 Remove transaction support from custom data sources
• WT-7295 Compatibility with older versions of WT

See JIRA changelog for a full listing: https://jira.mongodb.org/projects/WT/versions/24082

WiredTiger release 3.2.1, 2019-08-27

See the upgrading documentation for details of API and behavior changes.

Significant changes:

• WT-3968 Use compression ratio to tune page sizes
• WT-4156 Add a new salvage API option to wiredtiger_open
• WT-4192 Remove support for raw compression in WiredTiger
• WT-4426 Change WiredTiger data format to optionally include timestamps in cells
• WT-4447 Add a quota like system to manage I/O per subsystem
• WT-4494 Support import of of standalone WiredTiger files
• WT-4670 Remove support for LevelDB APIs in WiredTiger
• WT-4765 Remove support for Helium/Levyx data sources in WiredTiger
• WT-4803 Implement file_max configuration for Cache Overflow mechanism
• WT-4913 Fix the Windows CRC32 on blocks that aren't 8B aligned and/or multiples of 8B

See JIRA changelog for a full listing: https://jira.mongodb.org/projects/WT/versions/21117 https://jira.mongodb.org/projects/WT/versions/22515

WiredTiger release 3.1.0, 2018-07-12

See the upgrading documentation for details of API and behavior changes.

See JIRA changelog for a full listing: https://jira.mongodb.org/projects/WT/versions/19708

WiredTiger release 3.0.0, 2018-01-08

See the upgrading documentation for details of API and behavior changes.

Significant changes:

• WT-3039 Change the log file format to record a previous LSN record
• WT-3181 Add support for application defined transaction IDs via a mechanism called timestamps.
• WT-3310 Add support to WT_SESSION::alter to change table log setting
• WT-3389 Restructure page split code to hold a split generation for the entire operation.
• WT-3406 Fix a bug in reconciliation so that it ignores concurrent updates.
• WT-3418 Fix a block manager race in tree close/open
• WT-3435 Improvements to the cache overflow mechanism aka lookaside
• WT-3437 Improvements to auto tuning of number of eviction workers
• WT-3440 Add a log record when starting a checkpoint.
• WT-3461 Avoid hangs when system clocks move backwards by using CLOCK_MONOTONIC for pthread_cond_timedwait if possible.
• WT-3490 Fix a bug in WT_CURSOR.modify unaligned size_t access.
• WT-3495 Fix a bug so we don't ftruncate if log cursors are open
• WT-3497 Improve logging message when hitting the configured session limits
• WT-3537 Split pages in memory when nothing can be written
• WT-3556 Remove wtstats support
• WT-3681 Change recovery so that it doesn't truncate the last log file
• WT-3683 Allow eviction of clean pages with history when cache is stuck
• WT-3710 Get a page-level lock to ensure page splits are single threaded
• WT-3752 Allow trimming of obsolete modify updates.

See JIRA changelog for a full listing: https://jira.mongodb.org/projects/WT/versions/18401

WiredTiger release 2.9.3, 2017-06-27

See the upgrading documentation for details of API and behavior changes.

Significant changes:

• WT-2972 Add an interface allowing partial updates to existing values
• WT-3063 Add an interface allowing reservation of records for read-modify-write
• WT-3142 Add a workload generator application
• WT-3160 Improve eviction of internal pages from idle trees
• WT-3245 Avoid hangs on shutdown when a utility thread encounters an error
• WT-3258 Improve visibility into thread wait time due to pages exceeding memory_page_max
• WT-3263 Allow archive on restart/recovery if clean shutdown
• WT-3287 Review WiredTiger internal panic checks
• WT-3292 Review/cleanup full-barrier calls in WiredTiger
• WT-3296 LAS table fixes/improvements
• WT-3327 Checkpoints can hang if time runs backward
• WT-3345 Improve rwlock scaling
• WT-3373 Access violation due to a bug in internal page splitting
• WT-3379 Change when pages can be split to avoid excessively slowing some operations

See JIRA changelog for a full listing: https://jira.mongodb.org/browse/WT/fixforversion/18291

WiredTiger release 2.9.2, 2017-05-25

See the upgrading documentation for details of API and behavior changes.

Significant changes:

• SERVER-16796 Increase logging activity for journal recovery operations
• SERVER-28168 Cannot start or repair MongoDB after unexpected shutdown.
• SERVER-28194 Fix a bug where a missing WiredTiger.turtle file can result in data loss
• WT-98 Update the current cursor value without a search
• WT-2439 Enhance reconciliation page layout
• WT-2898 Improve performance of eviction-heavy workloads by dynamically controlling the number of eviction threads
• WT-3097 Race on reconfigure or shutdown can lead to waiting for statistics log server
• WT-3106 Add truncate support to command line wt utility
• WT-3114 Avoid archiving log files immediately after recovery
• WT-3115 Change the dhandle lock to a read/write lock
• WT-3127 Fix a bug with CPU yield calls don't necessarily imply memory barriers
• WT-3135 Fix a bug with search_near() for index with custom collator
• WT-3137 Fix a hang in __log_slot_join/__log_slot_switch_internal
• WT-3144 Fix a bug where random cursor returns not-found when descending to an empty page
• WT-3148 Improve eviction efficiency with many small trees
• WT-3149 Change eviction to start new walks from a random place in the tree
• WT-3150 Reduce impact of checkpoints on eviction server
• WT-3152 Convert table lock from a spinlock to a read write lock
• WT-3157 Fix a bug in checkpoint/transaction integrity issue when writes fail.
• WT-3158 Fix structure packing on Windows.
• WT-3188 Fix error handling in logging where fatal errors could lead to a hang
• WT-3193 Close a race between verify opening a handle and eviction visiting it
• WT-3206 Fix a bug where core dump happened on NULL page index
• WT-3218 Fix a bug that could lead to unexpected checkpoint ordering failures
• WT-3243 Reorder log slot release so joins don't wait on IO
• WT-3262 Stop making schema operations wait for cache

See JIRA changelog for a full listing: https://jira.mongodb.org/browse/WT/fixforversion/17874

WiredTiger release 2.9.1, 2016-12-22

New features and API changes; refer to the API documentation for full details:

• SERVER-26545 Remove fixed-size limitation on WiredTiger hazard pointers. See the upgrading documentation for details
• WT-283 Add a new WT_SESSION::alter method that can be used to reconfigure table metadata
• WT-2670 Change the default file system access pattern advice for data files from random to no advice. Add access_pattern_hint configuration option for WT_SESSION::create API that can be used to advise the file system of expected access semantics. See the upgrading documentation for details.
• WT-3034 Add support for including updates when reading from named snapshots

Significant changes and bug fixes:

• WT-2960 Reduce likelihood of using the lookaside file, especially when inserting multi-megabyte values
• WT-3056 Allow projected table and join cursors to use primary keys
• WT-3070 Fix a bug in search_near on indexes

Other noteworthy changes since the previous release:

• WT-2336 Add a test validating schema operations via file system call monitoring
• WT-2402 Pad structures to avoid cache line sharing
• WT-2771 Add a statistic to track per-btree dirty cache usage
• WT-2833 Add projections to wt dump utility
• WT-2969 Possible snapshot corruption during compaction
• WT-3014 Add GCC/clang support for ELF symbol visibility
• WT-3021 Fixes for java log example, raw mode in java, and raw mode in log cursors
• WT-3025 Fix error path in log_force_sync
• WT-3028 Don't check for blocked eviction with in-memory workloads
• WT-3030 Fix a race between scans and splits reading the index hint
• WT-3037 Clean up some log slot comments
• WT-3048 WiredTiger maximum size warning uses the wrong format
• WT-3051 Remove external __wt_hex symbol
• WT-3052 Improve search if index hint is wrong
• WT-3053 Make Python use internal memory allocation again
• WT-3054 Make a PackOutputStream constructor that is compatible with the previous interface.
• WT-3055 When an AsyncOp is created, cache the whether the cursor is "raw"
• WT-3057 WiredTiger hazard pointers should use the WT_REF, not the WT_PAGE
• WT-3061 Syscall testing should support pwrite64 on Linux
• WT-3064 Minor tree cleanups: .gitignore, NEWS misspelling
• WT-3066 Minor code cleanups
• WT-3068 Copy artifacts of test runs in wtperf_run script
• WT-3068 Have Jenkins include specific files for copy rather than exclude
• WT-3069 Fix LevelDB APIs build failures
• WT-3071 Fixed sign-conversion compiler errors in Java and Python SWIG code
• WT-3075 Document and enforce that WiredTiger now depends on Python 2.7
• WT-3078 Test reconfiguration hang in the statlog server
• WT-3080 Python test suite: add elapsed time for tests
• WT-3082 Python test suite: shorten default run to avoid timeouts
• WT-3084 Fix Coverity resource leak complaint
• WT-3091 Add stats to test_perf001 test, so we can investigate what happened when it failed

WiredTiger release 2.9.0, 2016-09-06

New features and API changes; refer to the API documentation for full details:

• WT-2360 Add nesting and disjunction functionality to cursor joins
• WT-2552 Add a public API to allow custom filesystem implementations
• WT-2738 Remove the ability to change the default checkpoint name. See the upgrading documentation for details.
• WT-2711 Change the statistics log configuration options. Restrict where statistics log files can be created to remove security vulnerability. See upgrading documentation for details.
• WT-2764 Enhance the checkpoint implementation, which led to a change in default eviction settings. See the upgrading documentation for details.
• WT-2880 Add Zstandard compression support
• See the upgrading documentation for information about renamed and removed statistics.

Significant changes and bug fixes:

• WT-2026 Fix a bug where in-memory pages were allowed to grow too large
• WT-2343 Ensure we cannot rename/drop when a backup cursor is open
• WT-2520 Ensure WT_SESSION::verify does not alter tables
• WT-2576 Ensure variable-length column-store cannot out-of-order return
• WT-2664 Change eviction so any eviction thread can find candidates
• WT-2702 Resolve an issue where under high thread load, WiredTiger exceeds cache size
• WT-2731 Resolve an issue where raw compression can create pages that are larger than expected
• WT-2737 Allow reconciliation to scrub dirty pages rather than evicting them
• WT-2757 Fix a bug in column stores where it was not possible to retrieve the new record number after an append
• WT-2816 Improve eviction performance

Issues fixed in MongoDB:

• SERVER-23504 Resolve a resource leak
• SERVER-23588 Stop using _open_osfhandle on Windows
• SERVER-23659 Improve log error message at startup
• SERVER-23661 Fix an issue where $sample takes disproportionately long time on newly created collection
• SERVER-24306 Fix stall in log_flush switching to new files
• SERVER-24580 Add more eviction stats to track efficiency
• SERVER-24580 Enhance eviction when application threads are contributing
• SERVER-24971 Don't cache buffers after application eviction
• SERVER-25843 Remove a redundant test
• SERVER-25845 Resolve an explicit null dereferenced
• SERVER-25846 Resolve a dereference after null with a check
• SERVER-26753 Don't spin on a read-lock in a tight loop

Other noteworthy changes since the previous release:

• WT-2103 Add incremental backup testing to test/format
• WT-2330 Ensure In-memory configurations do not create on-disk collection files
• WT-2450 Resolve an issue where salvage releases pages, then explicitly evicts them. Which can race with the eviction server
• WT-2453 Add multiple eviction queues
• WT-2504 Remove READONLY conditional for base config
• WT-2505 Resolve clang analyzer warnings
• WT-2508 Ensure test programs should remove test directories on the "clean" target
• WT-2512 Change how wtperf throttle values per thread are calculated
• WT-2513 Fix a type conversion warning
• WT-2517 Resolve incorrect uses of setvbuf on Windows
• WT-2518 Optimization of LSM checkpoint handle acquisition
• WT-2522 Resolve incorrect format code in message
• WT-2525 Miscellaneous cleanups of In-memory configurations
• WT-2526 Prevent mixing and matching readonly file-handles and read/write data-handles
• WT-2528 Fix a style error in WiredTiger build
• WT-2529 Be less aggressive asserting in readonly connections
• WT-2531 Resolve a case where in-memory tables are wasting space in truncation
• WT-2532 Change the WT_STREAM_APPEND and WT_STREAM_LINE_BUFFER flags as they overlap
• WT-2533 Don't let in-memory tables return a zero size
• WT-2534 Use atomic add when allocating transaction IDs
• WT-2535 Extend test/format to test for transactions reading their writes
• WT-2537 Check for an old and new uninitialized LSN for recovery
• WT-2539 Make streams a separate handle type from files
• WT-2540 Separate stream and file handle methods
• WT-2542 Resolve fixed-length column store reconciliation overwriting original values
• WT-2544 Fix eviction stats when clear is used
• WT-2546 Change evict server to be smarter when it decides whether or not to evict pages
• WT-2547 Add eviction testing configurations for 1 thread
• WT-2548 Cap the amount of data handed to raw compression
• WT-2550 Add support for raw mode cursors in java
• WT-2553 Add some In-memory documentation and stress testing
• WT-2556 Fix a typo in the Java example code
• WT-2557 Ensure that we truncate logs before closing backup cursor
• WT-2558 Reorganize WT_PAGE structure
• WT-2559 Resolve a potential segfault in Windows logging code
• WT-2560 Add a rwlock to protect transaction state, don't spin on this lock
• WT-2562 Add sleep loop to adapt for slow machines like PPC
• WT-2565 Further limit the amount of data passed to raw compression
• WT-2566 Add explicit memory barriers to Lock/unlock operations
• WT-2567 Add a check to see if logging is enabled for truncate rather than assuming it is
• WT-2568 Add a backward compatible constructor for PackInputStream
• WT-2569 Ensure __win_handle_read is followed by a call to GetLastError()
• WT-2570 Minor lint and cleanups to code
• WT-2571 Join code clean up
• WT-2572 Ensure test/format doesn't select an incompatible set of options for in-memory options configured
• WT-2573 Resolve a potential case where a double free can occur
• WT-2574 Ensure test/format frees all allocated configure memory
• WT-2576 Ensure variable-length column-store cannot out-of-order return
• WT-2577 Resolve a potential double-free following an in-memory split
• WT-2579 Change so diagnostic only code can use file streams directly
• WT-2580 Fix potential SWIG naming conflict in Java
• WT-2581 Resolve a case where we fail to track saved updates during a page split
• WT-2582 Fix a case where eviction can return WT_RESTART when running in-memory
• WT-2584 Change to not use periods at the end of error messages
• WT-2586 Fix examples/ex_config
• WT-2589 Ensure we clear the cursor statistics for LAS when 'clear' is set
• WT-2592 Fix joins for the non-recno, non-raw case
• WT-2593 Free the dirlist at the end of the function
• WT-2595 Fix compiler warning in packing test
• WT-2598 Change so that in-memory has faster lookup on file names
• WT-2599 Split out the checksum code from the support directory
• WT-2600 Clean up test program includes
• WT-2602 In LSM, use the chunk size to set maximum page size in memory
• WT-2605 Add C tests used in testing joins
• WT-2609 Resolve incorrect "skips API_END call" error
• WT-2610 Reduce hazard pointer array size
• WT-2611 Modify wtperf to handle escaped quotes
• WT-2612 Ensure the dist/s_prototypes script does not create a debugging file
• WT-2613 Add WT_UNUSED to a variable to fix Windows compilation
• WT-2615 Enabling checkpoints in test/format leads to reduced concurrency
• WT-2616 Fix a deadlock with in-memory size lookups
• WT-2617 Don't use u_int in the example code. It's not Windows native
• WT-2621 Fix missing parentheses on call to __wt_errno
• WT-2622 Clear old position for all random lookups
• WT-2624 Fix example program build with MSVC 2013
• WT-2626 Fix MSVC 2015 snprintf redefinition
• WT-2627 Resolve Coverity complaints
• WT-2628 Ensure reconciliation doesn't return without unlocking the page lock
• WT-2629 Ensure stacks are not executable in assembly source
• WT-2630 Rename pluggable filesystem methods to avoid reserved names
• WT-2631 Ensure nullptr is not passed for parameters marked with attribute non-null
• WT-2632 Tolerate EBUSY when a checkpoint cursor is open
• WT-2637 Update file-extension documentation to cover not-supported cases
• WT-2638 Add extension to the Windows file system implementation
• WT-2644 Fix 'wt load -r' (rename) with LSM
• WT-2645 Move the complexity of dump from the dump utility to the metadata cursor
• WT-2646 Add checkpoint_wait configuration option to drop
• WT-2648 Change cache-line alignment for new ports
• WT-2651 Fix a Coverity found resource leak
• WT-2652 Remove unnecessary wt_ftruncate call
• WT-2653 Add display of device configuration to custom file-system example
• WT-2656 Fix GCC 4.7 compiler warnings
• WT-2658 Ensure we only include PPC-specific files in PPC builds
• WT-2659 Assorted lint and cleanup to csuite tests
• WT-2660 Fix a hang between eviction and connection close
• WT-2662 For spell check, strip out double quote literals, they confuse aspell
• WT-2664 Add ability for eviction workers to populate eviction queues
• WT-2665 Limit allocator fragmentation from the WiredTiger cache
• WT-2667 Add fops to Evergreen testing for Windows and Linux
• WT-2668 Create join statistics that are useful and are easy to understand
• WT-2671 Dump more information about the file layout in verify debug mode
• WT-2672 Handle system calls that don't set errno
• WT-2673 Stop automatically increasing memory page max
• WT-2674 Simplify metadata file check
• WT-2676 Don't use key size in column store in-memory splits
• WT-2677 Fix JSON output so only printable ASCII is produced
• WT-2678 Fix cases where metadata implies that an empty value is true
• WT-2682 Add option to configure WiredTiger with strict compiler flags
• WT-2683 Allow in memory storage engine to report zero disk usage
• WT-2685 Fix clear walk hazard pointer failure
• WT-2686 Report an error any time we fail to scan the log
• WT-2687 Provide ability for test suite to verify the exit status of the wt utility
• WT-2688 Improve build error messages when SWIG is unavailable
• WT-2689 Fix heap-use-after-free on cursor error path
• WT-2691 Use wrappers for ctype functions to avoid sign extension errors
• WT-2692 Fix race in file system example
• WT-2693 Ensure open_cursor error paths have consistent error handling
• WT-2695 Integrate s390x accelerated crc32c support
• WT-2696 Wait if we find an unbuffered flag without the size set yet
• WT-2698 Change flag into atomically manipulated field to avoid deadlock
• WT-2702 Block operations when the cache is 100% full
• WT-2704 Fix bug in diagnostic code tracking duration of stuck cache
• WT-2706 Fix lost log writes when switching files
• WT-2707 Add stricter checks in dist/s_label, and add some WT_ERR calls
• WT-2708 Fix a split child-update race with reconciliation/eviction
• WT-2709 Resolve a connection reconfigure segfault in __wt_conn_cache_pool_destroy
• WT-2710 WT_FILE_HANDLE_INMEM no longer needs an off field
• WT-2713 Document WT_PANIC so pluggable filesystems can panic
• WT-2715 Resolve random abort test failure with partial write
• WT-2719 Allow make check without verbose configured
• WT-2719 Fix memory leak in reconfig test
• WT-2720 Change the return codes in run.py to error on failures
• WT-2722 Escape regular expression meta-character so egrep works on all systems
• WT-2724 Pass in session address, not pointer to it
• WT-2728 Only verify the log file header during recovery
• WT-2729 Focus eviction on the largest trees in cache
• WT-2730 Btree can incorrectly match key slots on new pages
• WT-2731 Finer adjustment for page size with raw compression
• WT-2732 Coverity analysis defect 99665, Remove redundant test
• WT-2734 Improve documentation of eviction configuration settings
• WT-2739 pluggable file systems documentation cleanups
• WT-2743 Fixup new I/O thread count statistics
• WT-2744 Detect and ignore partial line
• WT-2746 Add a new statistic tracking I/O for checkpoints
• WT-2751 column-store statistics incorrectly calculates the number of entries
• WT-2752 Fix errors in wtperf config
• WT-2755 Fix for cases where tools treats size_t as 4B type
• WT-2756 Upgrade the autoconf archive package to check for swig 3.0
• WT-2757 Column tables behave differently when column names are provided
• WT-2759 Releasing the hot-backup lock doesn't require the schema lock
• WT-2760 Fix a bug in backup related to directory sync. Change the filesystem API to make durable the default
• WT-2762 Handle 'Y' as an options from wtperf monitor file
• WT-2763 Change test ID's in test_intpack to fix OS X test errors
• WT-2764 Fix a bug calculating the dirty percentage of cache
• WT-2765 Ensure indices are shown in the dump output
• WT-2766 Don't sweep LAS cache when aren't making progress in eviction
• WT-2767 In test/suite/run.py, add -s N option to run an individual scenario
• WT-2769 Update documentation to reflect correct limits of memory_page_max
• WT-2770 Add statistics tracking schema operations
• WT-2772 Adjust log.wtperf config. Remove unneeded config entries
• WT-2773 Ensure that search_near in an index finds exact matches
• WT-2774 Minor cleanups/improvements
• WT-2778 Enhance output formatting when running Python test suite
• WT-2779 Fix large pages getting generated with raw compression
• WT-2781 Don't take checkpoint lock if checkpoint_wait=0 for bulk cursor open
• WT-2782 Minor text changes for file system functions
• WT-2783 Clean up wtperf configuration object management
• WT-2785 Scrub dirty pages rather than evicting them single-page reconciliation
• WT-2787 Include src/include/wiredtiger_ext.h is problematic
• WT-2788 Do not touch memory already freed during a close API call
• WT-2791 Have evergreen upload artifacts for each build. Rename current artifacts to "Binaries"
• WT-2793 Enhance statistics related to overflow values
• WT-2795 Update documentation about read-only mode
• WT-2796 Fix a memory leak when using the lookaside table
• WT-2798 Fix data consistency bug with table creates during a checkpoint
• WT-2800 Fix incorrect error message
• WT-2801 Prevent eviction of metadata updates by a running checkpoint
• WT-2802 Copy values during commit before releasing snapshot
• WT-2803 Add VERBOSE=1 to all make check jobs
• WT-2804 Don't read values in a tree without a snapshot
• WT-2805 Avoid infinite recursion on error stream failure
• WT-2806 Fix an off-by-one allocation in wtperf
• WT-2807 Change the memory allocator for wtperf performance tests
• WT-2811 The checkpoint session should not ignore it's own transaction ID
• WT-2812 Verify cache_size before dividing to avoid division by 0
• WT-2813 Configure eviction dirty settings explicitly for LSM in test/format
• WT-2814 Add new single op truncate mode to wtperf
• WT-2816 General improvements to WiredTiger eviction performance
• WT-2817 Add wtperf conf to stress test checkpoints with updates
• WT-2818 Change the page visibility check when queuing pages for eviction
• WT-2820 Add gcc warn_unused_result attribute
• WT-2822 Simplify error handling by using a panic mutex in functions that cannot fail
• WT-2823 Support file handles without a truncate method
• WT-2824 Fix double concatenation the config strings
• WT-2826 Fix a clang38 false positive on uninitialized variable
• WT-2827 Set a reasonable minimum for log_size
• WT-2828 Change wtperf long tests to better match MongoDB workloads
• WT-2829 Fix missing define for BerkeleyDB
• WT-2831 Skip checkpointing if there have been no modifications
• WT-2832 Python test uses hard-coded temporary directory
• WT-2834 Fix sign-change warning with auto conversion from uint to int
• WT-2834 Shared bloom filters allow only a partial shortcut
• WT-2835 Stop WT_CONNECTION.leak-memory skipping memory map and cache cleanup
• WT-2838 Don't free session handles on close if leak memory is configured
• WT-2839 Remove cases ignoring return value of function
• WT-2840 Fix garbage values found with clang analysis
• WT-2841 Initialize verbose checkpoint timer at start of checkpoint
• WT-2842 Add explicit include in wtperf to resolve build warning
• WT-2843 If there is no truncate available, manually zero the log file
• WT-2846 Ensure that all resources are released when destroying a thread group
• WT-2846 Fixes for new thread group code
• WT-2847 Merge fair locks into read/write locks
• WT-2850 Fix clang 4.1 attribute warnings
• WT-2853 Don't force eviction if multiple cursors are pinning the page
• WT-2857 POSIX ftruncate calls should be use HAVE_FTRUNCATE define
• WT-2858 Rename wtperf's CONFIG structure
• WT-2859 Restructure statistics gathering macros
• WT-2863 Support UTF-8 paths on Windows
• WT-2864 Update reconfigure test to detect hangs
• WT-2865 Fix a bug where the eviction server could panic after a WT_NOTFOUND
• WT-2866 Don't set eviction stuck unless the cache is full
• WT-2867 Review and fix barrier usage in __lsm_tree_close
• WT-2868 Add sample_interval to checkpoint-stress.wtperf
• WT-2869 Fix a performance regression on secondaries
• WT-2870 Rename wtperf jobs for consistency
• WT-2871 Make verbose formats and argument types match
• WT-2872 Ensure tests with tiny caches don't get stuck due to the dirty trigger
• WT-2873 Refactor CRC32 code
• WT-2874 Change test_compact01 to avoid eviction
• WT-2875 Add environment variable to disable long csuite tests
• WT-2876 Add an oplog-like ability to wtperf utility
• WT-2878 Fix an issue where verbose changes affected performance
• WT-2881 Add -Wpedantic to clang compiler warning flags
• WT-2883 Remove potentially recursive call for verbose handleops
• WT-2885 Lint __wt_checkpoint_signal function
• WT-2886 Ignore dirty eviction settings when in_memory is true
• WT-2888 Switch functions to return void where possible
• WT-2892 Fix case where hot backup can race with block truncate
• WT-2894 Add wtperf stress workload that tries to induce negative scaling
• WT-2895 Reduce the runtime of make check testing with disable long
• WT-2896 Fix a resource leak
• WT-2897 Fix an issue where checkpoints can become corrupted on failure
• WT-2900 Add ARM8 build support to WiredTiger and fix ARM CRC assembler tags
• WT-2901 Make checkpoint scrubbing configurable
• WT-2902 Track per-tree the efficiency of eviction walks
• WT-2903 Change the eviction_scrub_target default to 15%
• WT-2904 Fix a bug where the reported checkpoint size could be many times data size
• WT-2904 Revert overly strong assertion
• WT-2905 Remove dead code
• WT-2907 Fixed java concurrent close test to have both insert threads and scan threads
• WT-2908 Add a dry-run option to python suite
• WT-2910 When running in-memory, only evict dirty pages
• WT-2911 Add support for gcc6
• WT-2912 Make –enable-strict run on the zseries test box
• WT-2913 Re-sort eviction queues if we find no new candidates
• WT-2914 In test/csuite program, added explicit call to wiredtiger_open to satisfy some linkers
• WT-2916 Fix and simplify s_whitespace
• WT-2917 Split wtperf's configuration into per-database and per-run parts
• WT-2918 The dist scripts create C files s_whitespace complains about
• WT-2919 Don't mask error returns from style checking scripts
• WT-2920 New eviction statistics
• WT-2921 Reset the count when the last hazard pointer is cleared
• WT-2923 Fix heap-use-after-free on address in compaction
• WT-2924 Ensure we are doing eviction when threads are waiting for it
• WT-2925 Change where the WT_THREAD_PANIC_FAIL flag lives
• WT-2926 WT_CONNECTION.reconfigure can attempt unlock of not-locked lock
• WT-2928 Don't give up when the urgent queue is half empty
• WT-2928 Eviction failing to switch queues can lead to starvation
• WT-2931 Enforce limits on dirty data for in-memory
• WT-2932 Add a configuration option allowing tables to ignore cache limits
• WT-2933 Fix a race between named snapshots and checkpoints
• WT-2937 Only do an eviction walk after a page has been taken from the current queue
• WT-2938 Change assembly file extensions from .S to .sx
• WT-2941 Improve test/format to use faster key-generation functions
• WT-2942 Verbose messages should not have newlines
• WT-2945 Occasional hang running reconfigure fuzz test
• WT-2946 Fix dist/s_docs being incompatible with OS X Xcode installation
• WT-2947 Replace test suite populate functions with *DataSet classes
• WT-2948 Simplify error handling by making __wt_epoch return never fail
• WT-2949 Add option to skip closing the connection after test runs
• WT-2950 Free all reconciliation memory between calls to eviction
• WT-2953 Only test for checkpoint/LAS collision if LAS was used
• WT-2954 Evict pages that exceed memory_page_max even if the transaction ID is stuck
• WT-2955 Add statistics tracking the amount of time threads spend waiting for high level locks
• WT-2959 Ensure WT_SESSION_IMPL is never used before it's initialized
• WT-2961 Add a version drop-down to the web version of the docs
• WT-2962 Allow configuration of builtin extensions
• WT-2963 Fix a race bounding eviction in small caches
• WT-2964 Alter evict walk to not fill all its slots with internal pages when running in aggressive mode
• WT-2965 Remove sleep and retry loop from __evict_exclusive
• WT-2968 Don't open file handles on backup
• WT-2971 Add details on raw-compression into WT documentation
• WT-2975 Fix a leak of statistics data when reopening handles
• WT-2976 Add a statistic tracking how long app threads spend reading and writing
• WT-2977 Remove stash and check code from LSM test
• WT-2984 Keep sufficient history in the metadata for queries
• WT-2985 Fix a race during checkpoint that can cause a core dump
• WT-2987 Fix a bug where opening a cursor on an incomplete table drops core
• WT-2988 Fix __wt_epoch potentially returning garbage values
• WT-2991 Fix Coverity REVERSE_INULL
• WT-2998 Add error messages to error returns that might be confusing
• WT-2999 Added contributed test case that demonstrated the leak
• WT-3000 Wait for previous writes on first write to new log file
• WT-3001 Fix WT_EXTENSION_API references that are named inconsistently
• WT-3002 Allow applications to exempt threads from eviction
• WT-3003 Don't generate log record and op types
• WT-3003 Fix doxygen comment blocks
• WT-3004 Lint, declare functions that don't return a value as void
• WT-3005 Add top-level .gitignore file
• WT-3008 Move wtperf stress jobs to new stress runner folder
• WT-3009 Remove the eviction_dirty_target from test/format runs with less than 20MB cache
• WT-3011 Fix __wt_curjoin_open() saving the wrong URI in the cursor
• WT-3012 Check a btree is LSM primary before switching
• WT-3012 Don't track the LSM Primary as part of dirty bytes in cache
• WT-3015 Change when we will evict internal pages
• WT-3016 Change how file size is determined during compact tests to allow
• WT-3017 Don't set NULL hazard pointers
• WT-3020 Always make LSM chunks evictable when they are switched out
• WT-3022 Change lsm_tree flags to fields to prevent race conditions
• WT-3023 Don't treat splits as eviction making progress
• WT-3024 Fix a hang on close caused by leaving a transaction ID pinned

WiredTiger release 2.8.0, 2015-03-24

The WiredTiger 2.8.0 release contains new features, new supported platforms, minor API changes and bug fixes.

New features and API changes; refer to the API documentation for full details:

• WT-60 Port WiredTiger to run on big endian platforms
• WT-2287 Add a new WT_SESSION.rebalance API
• WT-2333 Add a lock_wait configuration setting to WT_SESSION.drop to avoid blocking
• WT-2349 Add a readonly configuration setting to wiredtiger_open
• WT-2363 Remove built in support for bzip2 compression
• WT-2404 Add streaming pack/unpack methods to the extension API

Significant changes and bug fixes:

• WT-1801 Add a directory sync after rollback of a WT_SESSION::rename operation
• WT-2130 Improve on-disk page utilization with random workloads
• WT-2275 Fix a database corruption after truncate and crash
• WT-2264 High update workloads can cause checkpoints to never complete
• WT-2290 Improve effectiveness of WT_SESSION.compact
• WT-2361 Fix a bug in column-store where verify identifies out of order data
• WT-2367 Fix a bug in WT_CURSOR.next that could cause out-of-order key returns
• WT-2374 Fix a bug where a database was corrupted when restoring a backup
• WT-2381 Fix the dump utility to include the table configuration
• WT-2451 Allow the WiredTiger metadata to be evicted
• WT-2490 Fix a bug in column-store where search_near() returns the wrong key

Issues fixed in MongoDB:

• SERVER-21619 sys-perf: WT crash during core_workloads_WT execution
• SERVER-21833 Enhance WT_SESSION::compact to more reliably release space
• SERVER-21887 Enhance $sample to be faster on newly created collection
• SERVER-22676 Allow WiredTiger to open databases created by 3.0.0 or 3.0.1
• SERVER-22773 New CRC32 implementation on PowerPC
• SERVER-22831 Low query rate with heavy cache pressure and an idle collection

Other noteworthy changes since the previous release:

• WT-1517 Fix error handling around schema format edge cases
• WT-2060 Simplify aggregation of statistics
• WT-2073 Metadata cleanups
• WT-2099 Seeing memory underflow messages
• WT-2107 Add example code including an event handler
• WT-2113 Truncate test occasionally fails with unexpected EBUSY
• WT-2123 Don't clear allocated memory if not required
• WT-2173 Fix some cases where tiny caches could get stuck full
• WT-2177 Add an optional per-thread seed to random number generator
• WT-2198 Bulk load and column store appends
• WT-2215 WT_LSN needs to support atomic reads and updates
• WT-2216 Simplify row-store search loop slightly
• WT-2231 Pinned page cursor searches could check parent keys
• WT-2235 Add a unicode option to WiredTiger printlog utility
• WT-2242 WiredTiger treats dead trees the same as other trees in eviction
• WT-2246 Improve performance for column-store append searches
• WT-2247 Variable-length column-store in-memory page splits
• WT-2258 Stop WiredTiger pre-loading pages when direct-IO is configured
• WT-2259 Fix error handling when getting exclusive access to a btree
• WT-2262 Fix random cursor next so it is not skewed by tree shape
• WT-2265 WiredTiger related change in PowerPC specific code block in gcc.h
• WT-2272 Fix a bug in the sweep server that triggered an assertion
• WT-2276 Add a tool to decode checkpoint addr
• WT-2277 Remove WT check against big-endian systems
• WT-2279 Define WT_PAUSE(), WT_FULL_BARRIER(), etc when s390x is defined
• WT-2280 Add CRC32 Optimized code for PowerPC
• WT-2282 Error in wt_txn_update_oldest verbose message test
• WT-2283 Retry in txn_update_oldest results in a hang
• WT-2285 Enhance configure to set BUFFER_ALIGNMENT_DEFAULT to 4kb on Linux
• WT-2289 Fix a bug in btree search when doing a fast key check
• WT-2291 Random cursor walk inefficient in skip list only trees
• WT-2295 WT_SESSION.create does a full-scan of the main table
• WT-2296 Improve log algorithm for sync/flush settings
• WT-2297 Fix off-by-one error in Huffman config file parsing
• WT-2299 Clean up layering violation between btree and block manager code
• WT-2307 Fix a bug where internal page splits can corrupt cursor iteration
• WT-2308 Add support for custom extractor for ref_cursors in join cursor
• WT-2311 Add support for UltraSparc platform
• WT-2312 Fix a bug where re-creating a deleted column-store page can corrupt the in-memory tree
• WT-2313 Fix a bug in the sweep server
• WT-2314 Update page-swap error handling so that it is consistent
• WT-2316 Fix a bug in WT_CURSOR.prev where it could return keys out-of-order
• WT-2318 Enhance condition wait implementation to use less CPU on idle databases
• WT-2321 Fix a race between eviction and worker threads on the eviction queue
• WT-2322 Fix a bug in read-uncommitted join cursors where using Bloom filters is unsafe
• WT-2328 Update schema drop does to use the block manager interface for file removal
• WT-2331 Checking of search result for reference cursors before join
• WT-2332 Fix a bug in logging write-no-sync mode
• WT-2335 Fix a bug where parsing an invalid configuration string could segfault
• WT-2338 Disable using pre-allocated log files when a backup cursor is open
• WT-2339 Fix a bug in rebalance that caused database verification failure
• WT-2340 Add logging guarantee assertions
• WT-2345 Avoid creating tiny pages on disk when evicting small pages from cache
• WT-2346 Enhance checkpoint implementation so the schema lock is not held during I/O
• WT-2347 Fix some schema format edge cases in Java API
• WT-2352 Allow build and test without requiring lz4
• WT-2355 Fix minor scratch buffer usage in logging
• WT-2356 log scan advances to next log file on partially written record
• WT-2368 Fix a bug where row-store can pass invalid keys to collator functions
• WT-2369 Use C compiler to detect headers instead of C++ compiler
• WT-2371 Fix a bug where parent split cannot access the page after page-index swap
• WT-2372 WiredTiger windows builder fails with C4005 against the "inline" macro
• WT-2375 Add tests for custom collators
• WT-2378 Fix a hang in LSM when doing forced drop with the no wait option
• WT-2382 Fix a bug in join cursors with custom collator for 'u' format
• WT-2384 Fix a bug in join cursors where lt, le conditions for ordering could be wrong
• WT-2387 Fix cursor random unit test on Windows
• WT-2390 Fix the OS X build
• WT-2391 Enhance eviction so that it is less likely to evict pages from indexes
• WT-2394 Fix a bug in compact that meant we didn't always reclaim available space
• WT-2395 Fix a recovery failure with an LSM tree
• WT-2396 Fix a deadlock between table drop and checkpoint
• WT-2397 Fix a bug in cursor traversal where doing a reverse walk could skip records.
• WT-2399 Add test case that verifies cursor traversal
• WT-2409 Fix a minor performance regression in LSM
• WT-2410 Stop casting function pointers to different types
• WT-2411 Fix a hang in LSM related to dropping tables
• WT-2414 Avoid extractor calls for ordering cursor in join cursor
• WT-2417 Windows Jenkins task is failing
• WT-2418 Fix a bug in WT_SESSION.rebalance where it could return EBUSY
• WT-2420 Fix a bug in LSM where recovery from a backup could fail
• WT-2423 Fix a bug in session reference counting on error handling
• WT-2425 Fix a performance regression in wtperf evict-btree read workload
• WT-2426 Fix a deadlock caused by recent changes to checkpoint handle locking
• WT-2428 Make statistics logging compatible with MongoDB
• WT-2429 Add a statistic that tracks aggressive mode in eviction
• WT-2430 Add statistics for join cursor
• WT-2432 Fix a performance regression on LSM and read only workloads
• WT-2433 Allow read-only databases to log statistics
• WT-2434 Fix a race between force-drop and sweep
• WT-2436 Fix a bug in join cursors with lt, le conditions and "strategy=bloom"
• WT-2438 Extend WiredTiger stat declarations to help external tools
• WT-2440 Fix a bug in the PowerPC checksum implementation
• WT-2443 Add statistics for all indexes used in join cursor
• WT-2447 Enhance join cursor implementation to avoid reading main table where possible
• WT-2448 Add no_scale flag to relevant statistics
• WT-2449 Enhance configure to check for a 64-bit build
• WT-2454 Fix checkpoint_sync=false behavior to prevent flushes/sync to disk
• WT-2456 Fix PowerPC CRC32 Code
• WT-2457 Fix a bug where dropping an LSM table can return EBUSY when no user ops are active
• WT-2459 Allow configure to use the –tag option for libtool when compiling on PowerPC
• WT-2460 Fix a bug where checkpoint could fail with WT_ROLLBACK
• WT-2471 Update WiredTiger printf formats to be platform aware
• WT-2476 Fix a race where btree->evict_lock is being accessed after being destroyed
• WT-2481 Fix a recently introduced performance regression in LSM
• WT-2483 Make read only testing more robust
• WT-2485 Fix a test/format failure with floating point exception
• WT-2492 Fix a bug in Windows where we used the different memory allocators accidentally
• WT-2495 Missing memory initialization leads to crash on Windows
• WT-2496 Fix a bug revealed by test/format unable to read root page
• WT-2497 Enhance test/format to save a copy of backup
• WT-2498 Fix a bug in LSM tree drop where it could hang when a user cursor is open
• WT-2499 Fix a bug in LSM shutdown where a race condition causes a segfault
• WT-2501 Fix a bug where dropping a just opened LSM tree isn't thread safe
• WT-2502 Fix a memory leak in locking handles for checkpoint

WiredTiger release 2.7.0, 2015-12-08

The WiredTiger 2.7.0 release contains new features, minor API changes and bug fixes.

New features and API changes; refer to the API documentation for full details:

• WT-147 Create indexes on non-empty tables.
• WT-1315 Add an implementation of cursor joins via a new WT_SESSION::join API.
• WT-1350 Add a new configuration option to wiredtiger_open and WT_CONNECTION::reconfigure called "eviction_dirty_trigger" that causes eviction to start evicting dirty pages from cache once the given threshold has been reached.
• WT-1728 Add a WT_SESSION::reset method to release resources held by a session.
• WT-1930 Allow setting "file_manager=(close_idle_time=0)" to wiredtiger_open and WT_CONNECTION::reconfigure to disable closing idle handles.
• WT-1959 Change verify to distinguish between warnings and errors. Add a new strict mode to verify that causes warnings to be reported as errors. Use strict mode to match earlier behavior. See the upgrading documentation for more information.
• WT-1980 Add a new "metadata:create" URI to WT_SESSION::open_cursor for metadata cursors that return strings useful for passing to WT_SESSION::create.
• WT-2065 Add a new configuration option to wiredtiger_open and WT_CONNECTION::reconfigure called "shared_cache=(quota)" that limits the amount of shared cache a participant can be assigned.
• WT-2104 Add a method to flush log files via a new WT_SESSION::log_flush API. Made WT_SESSION::commit_transaction configuration options match WT_SESSION::log_flush. Change the default WT_SESSION::transaction_sync timeout to 20 minutes rather than infinity.
• WT-2151 Enhance logging configuration to allow reconfiguration and add a new "log=(zero_fill)" configuration option that causes WiredTiger to zero-fill log files on creation.
• WT-2200 Add a new configuration option to wiredtiger_open called "write_through" that causes WiredTiger to specify the FILE_FLAG_WRITE_THROUGH on Windows when writing files (default false, including when "direct_io" is configured).
• WT-2217 After a successful call to WT_CURSOR::insert, the key and value will be cleared from the cursor. See the upgrading documentation for more information.
• SERVER-17078 Add a "statistics=(size)" mode to statistics cursors, which allows for retrieving file size only.
• SERVER-18356 Changed the handling of the "config_base" option to wiredtiger_open. See upgrading documentation for more information.

The following statistics were removed:

• WT-1481 connection dhandles swept.
• WT-1481 connection candidate referenced.
• WT-1481 failed to find a slot large enough for record.
• WT-1989 log buffer size increases.
• WT-1989 slots selected for switching that were unavailable.
• WT-2094 log records written directly.
• WT-2094 record size exceeded maximum.
• WT-2182 pages split during eviction.

Lookaside table:

• WT-1967 Allow eviction of updates required by old readers.
• WT-2074 Fix a race between lookaside table reconciliation and checkpoints.
• WT-2149 Fix the order of creation of the lookaside table.
• WT-2190 Fix transaction visibility test that is applied to the lookaside table.
• SERVER-21585 Don't use the lookaside file until the cache is stuck full.

Issues fixed in MongoDB:

• SERVER-18829 Have pages start in the middle of the LRU queue for eviction.
• SERVER-18838 During drops, don't remove files until the metadata is durable.
• SERVER-18875 Clean up deleted pages.
• SERVER-18899 Add unit test to simulate fsyncLock.
• SERVER-19340 Avoid type aliasing in the random number generator.
• SERVER-19445 Have the oldest transaction update the oldest tracked ID.
• SERVER-19522 Try to evict internal pages with no useful child pages.
• SERVER-19573 Change row-store inserts to avoid page locking.
• SERVER-19751 Retry pthread_create on EAGAIN or EINTR.
• SERVER-19954 Don't scan tracked handles during checkpoints.
• SERVER-19989 Add a write barrier before data handles are added to shared lists.
• SERVER-19990 Don't assert on eviction of live updates from dead trees.
• SERVER-20008 Don't reset eviction walks when hitting a busy page.
• SERVER-20159 Make all readers wait while the cache is full.
• SERVER-20193 Fix obsolete transaction check.
• SERVER-20303 Tune in-memory splits when inserting large objects.
• SERVER-20385 Make WT_CURSOR::next(random) more random.
• SERVER-21027 Reverse split if there are many deleted pages.
• SERVER-21553 Enable fast-path truncate after splits.
• SERVER-21619 Don't do internal page splits after a tree is marked DEAD.
• SERVER-21691 Avoid insert stalls.

Other note worthy changes since the previous release:

• WT-1744 Throttle worker threads based on eviction targets.
• WT-1845 Allow read only transactions to commit after failure.
• WT-1869 Avoid doing in memory splits while checkpointing a tree.
• WT-1942 Add atomic implementations for PowerPC architecture.
• WT-1962 Make the hot_backup_lock a read/write lock.
• WT-1963 Fix backup cursor Java API.
• WT-1964 Fix a bug in the Java API when closing handles from a different thread.
• WT-1966 Change how the shared cache assigns priority to participants.
• WT-1975 Ensure previous log files are complete for forced sync.
• WT-1977 Improve performance of getting snapshots with many sessions.
• WT-1978 Better checking and tests for index cursor comparison.
• WT-1981 Fix a signed 32-bit integer unpacking bug.
• WT-1982 Fix a bug where cached overflow items were freed too early.
• WT-1985 Integer packing and other fixes for Python and Java.
• WT-1986 Fix a race renaming temporary log files.
• WT-1989 Improve scalability of log writes.
• WT-1996 Fix a bug where we would free the fist update during a page rewrite on error.
• WT-1998 Fixes for indexes with some rarely used key/value formats.
• WT-2002 Fix a bug in verify where it would panic when encountering a corrupted file.
• WT-2007 Statically allocate log slot buffers to a maximum size.
• WT-2008 Fix a bug in recovery where a file create went missing.
• WT-2009 Apply tracked metadata operations post-commit.
• WT-2012 Fix a bug updating the oldest ID.
• WT-2013 Add gcc asm definitions for ARM64.
• WT-2014 Fix a bug in checkpoints where files could be flushed in the wrong order.
• WT-2015 Fix a bug in error handling during block open.
• WT-2017 Once an eviction server thread is started keep it running.
• WT-2019 Fix a logic bug tracking the maximum transaction ID in clean trees.
• WT-2020 Clarify checksum error failure messages.
• WT-2021 Fix a bug moving the oldest ID forward (introduced by WT-1967).
• WT-2022 Fix a bug not releasing a handle when opening a non-existent index cursor.
• WT-2023 Improve locking primitives: simplify read-write lock operations.
• WT-2029 Improve scalability of statistics.
• WT-2031 Log slot revamp.
• WT-2032 Improve next_random cursors to work with small trees.
• WT-2034 Improve shared cache balancing algorithm.
• WT-2035 For index cursors, keep track of which column groups need to be positioned.
• WT-2036 Make handle sweeps more robust.
• WT-2037 Only write a checkpoint to the log on close if it wasn't.
• WT-2038 Avoid long scans holding the handle list lock.
• WT-2039 Add error check and unit test for log records over 4 GB.
• WT-2042 Only try to evict tombstones that are visible to all readers.
• WT-2045 Don't let the eviction server do slow reconciliation, it can stall eviction.
• WT-2046 Add a statistic for search restarts.
• WT-2047 Fix a bug in the random generator code to handle an uninitialized state.
• WT-2050 Show size with memory allocation errors.
• WT-2053 Fix a bug in disk verify messages.
• WT-2056 Reorder btree cursor close so stats are maintained correctly.
• WT-2057 Remove the verbose configuration when writing the base configuration file.
• WT-2058 Fix an alignment bug in the mutex and log-slot code.
• WT-2059 Include non-aggregated stats in cursor results.
• WT-2062 Try harder to make progress on in-memory splits.
• WT-2064 Don't spin indefinitely waiting for the handle list lock in eviction.
• WT-2066 Update the oldest transaction ID from eviction.
• WT-2068 Protect discarding handles with the handle list lock.
• WT-2075 Fix a hang in logging with parallel workload.
• WT-2078 Fix a bug in error handling with statistics cursors.
• WT-2081 Make verify progress reporting less verbose.
• WT-2085 Run some of the log_server threads operations more frequently.
• WT-2086 Add a statistic to track when eviction finds a page that can be split.
• WT-2089 Relax restrictions on multiblock eviction and in-memory splits.
• WT-2090 Fix a bug in the Windows OS layer that swallowed error returns.
• WT-2092 Free log condition variables after all threads are joined.
• WT-2093 Use the C99 bool type to clarify when functions return true/false.
• WT-2094 Eliminate direct write and record unbuffered log records.
• WT-2097 Reintroduce immediate waits when forced eviction is necessary.
• WT-2100 Rename evict to evict_queue so it's easier to search for.
• WT-2101 Don't update the logging ckpt_lsn on clean shutdown.
• WT-2102 Fix a hang in log slot join when forcing log writes.
• WT-2105 Fix a bug where we could reference an invalid memory address if a file is corrupted on disk.
• WT-2108 Rework in-memory page rewrite support (WT_PM_REC_REWRITE).
• WT-2114 Make application eviction fairer.
• WT-2115 Don't skip truncated pages that are part of a checkpoint.
• WT-2116 Add diagnostic checks for stuck cache and dump the state.
• WT-2119 Don't evict clean multiblock pages with overflow items during checkpoints.
• WT-2126 Clean up if there is an error during splits.
• WT-2127 Deepen the tree more regularly to avoid wide internal pages.
• WT-2128 When decoding huffman encoding during salvage it's possible to have fewer bits than the symbol length during decoding, if the value has been corrupted.
• WT-2131 Switch to using a lock to control page splits to avoid starvation.
• WT-2132 Make debug dump function more robust to errors.
• WT-2134 Flush all buffered log records in log_flush.
• WT-2135 Fix log_only setting for backup cursor. Fix initialization.
• WT-2137 Check the sync_lsn is in the correct file before moving it forward.
• WT-2139 Fix a transaction visibility bug in read-uncommitted transactions.
• WT-2146 Improve performance when searching for short keys.
• WT-2148 Fix a compiler warning in encoding functions.
• WT-2153 Fix bug. Now we always need to start the log_server thread.
• WT-2154 Make btree dump safer.
• WT-2155 Remove last use of F_CAS_ATOMIC and the associated macro.
• WT-2156 Allow eviction workers to restart.
• WT-2157 Fix a bug where a failed page split could lead to incomplete checkpoints.
• WT-2159 Don't check the config twice in one path.
• WT-2162 Add null pointer check, needed after an index is dropped.
• WT-2164 Prevent another LSM chunk checkpoint while the first is still in progress.
• WT-2165 Stop using FALLOC_FL_KEEP_SIZE flag when pre-allocating files.
• WT-2167 Switch recovery to using an internal session.
• WT-2170 Protect the turtle file with a lock.
• WT-2174 Avoid the table list lock when creating a size only statistics cursor.
• WT-2178 In-memory storage engine support.
• WT-2179 Added decorator to mark txn13 as part of the –long test suite.
• WT-2180 Remove cursor.{search,search-near,remove} key size validation.
• WT-2182 When internal pages grow large enough, split them into their parents.
• WT-2184 Fix log scan bug when final record has many trailing zeros.
• WT-2185 Don't do reverse splits when closing a file.
• WT-2187 Add flag for flushing a slot.
• WT-2189 Update flag set and clear macros to be less error prone.
• WT-2191 In-memory disk image no longer the same as saved updates.
• WT-2192 Fix the logic around checking whether internal page is evictable.
• WT-2193 Handle read-committed metadata checkpoints during snapshot transactions.
• WT-2194 Java close callbacks should handle cursors that Java code did not open.
• WT-2195 Fix a hang after giving up on a reverse split.
• WT-2196 Fix error handling in size only statistics.
• WT-2199 Fix transaction sync inconsistency.
• WT-2203 Release an allocated page on error.
• WT-2204 Don't take a local copy of page->modify until we know the page is dirty.
• WT-2206 Change cache operations from flags to an enumeration.
• WT-2207 Track whenever a session has a handle exclusive.
• WT-2210 Raw compression fails if row-store recovery precedes column-store recovery.
• WT-2212 Add a "use_environment" config to wiredtiger_open.
• WT-2218 Add truncate stats.
• WT-2219 Enhancements to in-memory testing.
• WT-2220 Update time comparison macros.
• WT-2222 Add statistics for named snapshots.
• WT-2224 Track which deleted refs are discarded by a split.
• WT-2228 Avoid unnecessary raw-compression calls.
• WT-2237 Have threads publish unique transaction IDs so that updates always become visible immediately on commit.
• WT-2241 Use a lock to protect transaction ID allocation.
• WT-2243 Don't keep transaction IDs pinned for reading from checkpoints.
• WT-2244 Trigger in-memory splits sooner.
• WT-2248 WT_SESSION::close is updating WT_CONNECTION_IMPL.default_session.
• WT-2249 Keep eviction stuck until cache usage is under 100%.
• WT-2250 Minor fix. Use SET instead of increment for stat.
• WT-2251 Free addresses when we discard deleted page references.
• WT-2253 Evict pages left behind by in-memory splits.
• WT-2257 Fixes when given multiple thread workload configurations.
• WT-2260 Avoid adding internal pages to the eviction queue

WiredTiger release 2.6.1, 2015-05-13

The WiredTiger 2.6.1 release contains new features, minor API changes and bug fixes.

New features:

• Move the sync configuration setting from WT_SESSION::begin_transaction to WT_SESSION::commit_transaction. Change the setting from a boolean to a string. See upgrading documentation for more information. refs WT-1908
• Add the ability to flag a transaction to be flushed asynchronously on commit via a new sync=[background] configuration option. Add a new WT_SESSION::transaction_sync API to wait for asynchronous flushes to complete. refs WT-1908, #1943
• Add the ability to create a named in-memory snapshot via a new WT_SESSION::snapshot API. refs WT-1839
• Add the ability to disable write ahead logging at a per-table granularity. Accessed via log=(enabled) configuration for WT_SESSION::create API. Partial logging has serious implications for recovery, it should be used with caution. refs #1989

Other noteworthy changes:

• Fix several bugs related to syncing files for checkpoint durability. refs WT-1944
• Fix a segfault during checkpoint where we could attempt to access a file that was in the process of being dropped in the background. refs SERVER-18014
• Fix a segfault during eviction where we could attempt to evict a page from a tree that was in the process of being dropped in the background. refs SERVER-18460
• Fix a bug where WiredTiger could segfault in a workload with lots of cache pressure. refs WT-1937
• Fix a performance issue with WT_SESSION::compact, where it would spend a long time compacting tables that had no space to reclaim. refs WT-1953
• Fix a bug where accessing an overflow item could return WT_NOTFOUND incorrectly. The issue was related to an invalid transaction visibility check. refs WT-1745
• Improve performance and avoid changing files on startup if no recovery is required by avoiding the creation of unnecessary checkpoints and log records for files that haven't changed. refs WT-1936
• Improve how we handle create of a table, if a file with the same name already exists (possibly from an earlier failed create). refs #1974
• Fix compiler warnings for LZ4 implementation on Windows. refs #2006
• Fix a bug in the WiredTiger command line utility where it could create a base configuration file for an existing database, if there had been a crash while creating the database. refs WT-1943
• Fix a build problem where recent versions of RedHat would fail to detect posix_memalign presence correctly. refs WT-1951
• Fix several problems with how we create, recover and backup databases. Related to order of creation and differences between Windows and POSIX file system semantics. refs #1993
• Fix a bug where we could flush the log file more often than required if using auto-commit transactions. refs WT-1949
• Fix a performance problem in LSM, where trees created with an initial bulk load could choose poor merges. refs WT-1947
• Improve how we decide whether to deepen a tree during an internal split operation. Append workloads could create trees that were excessively deep.
• Fix a bug in LSM which could lead to a hang on connection close. refs WT-1935
• Fix a bug in the internal random number generator, where concurrent calls could lead to invalid sequences. Never seen in the wild.

WiredTiger release 2.6.0, 2015-05-13

The WiredTiger 2.6.0 release contains new features, minor API changes and many bug fixes.

New features:

• Add support for "at rest" encryption of WiredTiger databases via a new encryption API. refs WT-1822
• Add support for bulk load in LSM trees (previously the bulk configuration for cursor create was ignored by LSM trees). refs SERVER-18321, WT-1922
• Add enhanced compression support for LZ4. Change is not compatible with tables created with LZ4 compression using earlier versions of WiredTiger. See the upgrading documentation for more information.

API and behavior changes:

• Enhance performance of WT_SESSION::drop with force enabled (mark the table as dead and discard it in the background without writing any content to disk, rather than flushing content from the cache). refs WT-1894
• Add an API to validate configuration strings. refs WT-1739
• Disallow the cache_resident flag on LSM trees. refs WT-1905
• Enhance the controls for how aggressively idle handles are closed, update the wiredtiger_open file_manager configuration options to expose that control. refs SERVER-17907, WT-1856

Significant bug fixes and performance enhancements:

• Fix bugs in checkpoint: committing the checkpoint transaction before it was safe, failure to sync the metadata file before updating the turtle file. refs SERVER-18316
• Don't attempt to validate configuration settings for extensions (collators, compressors, encryptors, extractors). The extension may be valid but not yet loaded so it is not possible to validate.
• Check the magic and version numbers in log files when first opening them.
• Fix a bug with cache leaf size accounting for statistics. refs WT-1885, WT-1919
• Fix a bug where checkpoint could skip a page that was rewritten in memory. refs WT-1946
• Fix a bug in WT_CURSOR::search_near with a random cursor where deleted records could be returned. refs WT-1921, WT-1944
• Fix a bug in handle close where we could fail to clear the open handle flag. refs WT-1915
• Fix a bug in in-memory splits, don't allow any other eviction of a page if the page is being split. refs WT-1916, WT-1917
• Fix a bug in btree open where failure while opening a checkpoint may not clean up completely. refs WT-1598
• Fix a performance problem where long running transactions could continually scan long update chains looking for obsolete entries, when there is no chance of finding any. refs WT-1913
• Fix a performance problem where many threads accessing a single page could prevent WiredTiger from evicting or splitting the page. refs WT-1912
• Fix a source of deadlock bugs by restructuring how we lock handles. Clean up the definition of when it is safe to acquire different locks. refs WT-1598
• Fix a bug where we could evict pages from a file marked as cache resident, add optimizations for cache resident files. refs SERVER-18192
• Fix a deadlock related to LSM (cases where closing a file with an existing checkpoint could self deadlock). refs WT-716
• Only split large in-memory pages if there is a need to keep them in cache (otherwise, it is better to reconcile and evict them immediately). refs WT-1890, WT-1896
• Fix a race on shutdown where the eviction server could still have been accessing files while they were being closed. refs WT-1893
• Fix a case where we could run recovery unnecessarily if there were only non-data changing log records since the last checkpoint. refs WT-1892
• Update API documentation to explain internal session handle usage. This allows users to do specific calculations based on the session_max setting.
• Fix a bug in LSM where updates with overwrite could be skipped incorrectly. refs BF-829
• Fix a cursor bug where searching and traversing in different combinations could lead to data buffers being freed before they should be. refs WT-1887
• Fix a bug when closing bulk cursors, where a file could be left open.
• Fix a bug on Windows related to truncating files (SetEndofFile does not ignore truncation requests like POSIX fallocate).
• Fix a bug in file truncate, where we could truncate to the wrong place if there was a race extending the file at the same time. refs WT-1871
• Fix a bug in reconciliation where page boundary structures could reference freed memory. refs WT-1852
• Change the WT_CURSOR::search and WT_CURSOR::search_near API to first check any currently pinned page before starting a regular descending search.
• Fix a bug in recovery where an error was returned if a transaction spanned an entire log file.
• Fix a bug where recovery could be unnecessarily run during startup.
• Enhance the Python cursor API to allow setting keys and values using array notation.
• Fix a bug where creating a column store with large gaps in the key range would lead to poor performance. refs WT-1807.
• Improve the performance of the core btree search routine by using low-level x86 vectorized search instructions.

WiredTiger release 2.5.3, 2015-04-22

The WiredTiger 2.5.3 release contains important bug fixes.

API and behavior changes:

• Update configuration string parsing to always be case sensitive. See upgrading documentation for more information.
• Change the statistics cursor WT_CURSOR::reset method to re-load statistics values. See upgrading documentation for more information. refs WT-1533
• Only align buffers on Linux if direct I/O is configured. See upgrading documentation for more information.
• Fixes to how and when idle handles are closed. refs WT-1808, WT-1811, WT-1814
• Add some new statistics related to cache usage.
• Add new configuration strings to provide control of how often handles are are reviewed for closure, and how long a handle needs to be idle before it is closed. The option is via the wiredtiger_open API, file_manager=(close_idle_time=30,close_scan_interval=10)
• Add support for running WiredTiger command line utilities without logging. refs WT-1732
• Update the async configuration API to allow a minimum of 1. That is change: async=(ops_max=X) so that the minimum value is now 1 the old minimum was 10.

Bug fixes and other significant changes:

• Fixes and improvements to Windows support.
• Fix several bugs that prevent page eviction. refs SERVER-16662, SERVER-17382, WT-1777
• Fix a race when stopping eviction workers on shutdown. refs WT-1698
• Fix a bug where if the system crashes during create the base configuration file could be left in an invalid state. refs WT-1775, WT-1776, SERVER-17571
• Fix cases where WT_SESSION::truncate could return EBUSY when a schema level operation is running - for example a checkpoint. refs WT-1404, WT-1643
• Fix a bug in logging - where we could fail to update the end of the log when there is a gap in the log records. refs WT-1766, SERVER-17569, SERVER-17613
• Fix how we account for space used in the cache to be more accurate. refs SERVER-17424
• Fix a bug where we could leak memory if opening a statistics cursor failed. refs WT-1760
• Fix a bug where a single page could consume a large portion of the cache. Leading to cases where a small cache size could result in a hang. refs WT-1759
• Fix a bug in the eviction server that could cause a WT_PANIC. The issue was encountered when the number of open handles exceeded the configured number of hazard pointers. refs SERVER-17551
• Fix a bug parsing huffman configuration options that could lead to a segfault.
• Fix accounting in btree statistics gathering, so page tracking is accurate. refs WT-1733
• Fix a memory leak in cache management, where a race during page split could leave a key structure allocated. refs WT-1582, WT-1747
• Enhance checkpoint tracking code to allow eviction in files once the checkpoint has finished processing them. This helps reduce the impact of checkpoints on workloads with cache pressure. refs WT-1745
• Fix when aggregation is set on statistics fields. Fixes problems with visualizing statistics via wtstats graphs. refs WT-1742
• Change how checkpoints use empty blocks in on-disk files. Use a first-fit algorithm.

WiredTiger release 2.5.2, 2015-03-23

The WiredTiger 2.5.2 release contains important bug fixes.

API changes:

• Allow memory_page_max to be at most a quarter of the cache size not half. This avoids operations getting stalled due to the cache being filled with one or two pages.

Bug fixes and other important changes:

• When skipping a dirty page during a checkpoint, make sure the tree is marked dirty. refs SUPPORT-1248, SERVER-17319, SERVER-17506, #1404, #1643, #1721, #1735
• Fix a bug in range truncate where we could remove the wrong records. refs SERVER-17345
• Fix a bug in LSM management where we could let the cache get full - leading to a operations being blocked. refs #1720
• Fix several bugs in the checkpoint implementation that could lead to a tree being marked clean when it had updates in memory. If shutdown occurred at a specific time those updates would be discarded without being written. refs SUPPORT-1248
• Fix some bugs in logging - where system crashes could leave empty files that would stop recovery working on re-start. refs #1717, #1719, SERVER-17451
• Fix a bug in recovery. Force recovery instead of returning an error if the LSN given doesn't exist. refs #1700, #1704
• Move writing into log worker thread to avoid latency in application threads. refs #1683
• Fix a bug in the reconfigure API related to adhering to shared cache quotas. refs #1712, #1713
• Fix a bug in WiredTiger statistics where we weren't recording overflow record statistics. refs #1520, #1703, #1711
• Several enhancements to eviction of large pages including:
  • Don't do forced eviction of a page if it is the current walk point.
  • Don't update the read generation on page in if it's set to oldest.
  • Clear the walk positions before the eviction server sleeps.
  • Reverse the direction of the LRU walk regularly.
  • Add all pages that would block to the eviction queue.
  • If evicting dirty pages use the worker threads not the server. refs #1706
• Use raw mode when dumping indices. refs #1709
• Fix a bug where we could race opening files while a WT_CONNECTION::close is in progress. refs SERVER-17319
• Fix a bug in LSM where snapshot transaction updates could have the wrong visibility check applied. Leading to invalid updates. refs #1641, #1701, #1702
• Fix a bug in checkpoint where it could get an EBUSY return unnecessarily. refs #1404, #1589, #1705
• Fix a bug when writing a page from memory to disk (reconciling). We could overwrite the end of a temporary buffer in some cases. refs #1697, #1699
• Sometimes we would choose a sub-optimal layout for on disk pages when writing them out from memory. refs #1699
• Improve the performance of in-memory lookups by making the content of the page structure more cache friendly.

WiredTiger release 2.5.1, 2015-03-07

The WiredTiger 2.5.1 release contains new features, minor API changes and many bug fixes.

New features and API changes:

• Add a new "log=(recover=on)" option to wiredtiger_open. The default value is "on", if set to "error", recovery won't be run on startup. An error will be returned if recovery is needed but disabled. This option is mainly to support the WiredTiger command line utility. refs #1651
• Add a new WT_CURSOR::equals method that returns when the cursors are equal, intended as a fast-path for cursor comparison.
• Change how statistics work when there are checkpoints for an object. We used to aggregate statistics for all open checkpoints and the current handle. We now only return statistics for the object being queried. See upgrading documentation for further information.
• Add a mode to LSM that allows us to limit the size of a tree by dropping old chunks. Enabled via "lsm=(chunk_count_limit=0)", default to 0 which disables the functionality. Note that enabling this feature discards old data automatically. refs #1652
• Update the WiredTiger printlog command line utility to generate JSON that can be parsed by third party tools. refs #1438
• Change how we track memory allocation overhead. We used to apply a fixed size for each allocation (which was difficult to track). The overhead can be specified via a new configuration option to wiredtiger_open using "cache_overhead=8". The value is a percentage and the default is 8. refs #1564 #1565
• Major enhancements to the wtstats.py tool that translates WiredTiger statistics into an HTML graph. The tool now generates interactive graphs and no longer requires third party Python libraries to be installed.
• Add a new WT_CURSOR::reconfigure method for cursor configuration. See API documentation for more information. refs #1381
• Add a new WT_SESSION::strerror method, a thread-safe alternative to wiredtiger_strerror. refs #1516

Bug fixes for bugs that could cause data inconsistency:

• Fix a bug in recovery where we could lose track of file identifiers and apply updates to the wrong file. refs SERVER-17142 SERVER-17131
• Fix several bugs in data consistency that could cause corruption when restarting after a hard crash, including:
  • A bug in table create that could cause recovery to fail. refs SERVER-17204

Other significant changes:

• Significant tuning enhancements for the WiredTiger cache, including:
  • Avoiding stalls due to evicting large pages
  • Better algorithms for getting application threads to help with cache management without interfering with operation latencies.
  • Better algorithms for maintaining the cache when there are a few very hot pages (e.g: append workloads). SERVER-17344
  • Freeing obsolete references more aggressively, which saves space and reduces traversal overhead when there are lots of updates or deletes. refs SERVER-17195, #1647
  • Fix a bug that could cause a data loss if we split a large page into multiple smaller pages and attempted to evict the page at the same time. refs #1583 #1563 SERVER-16868
• Significant improvements to the cursor truncate implementation, especially for workloads that periodically truncate from the start of the file. refs SERVER-17141
• Fix a bug in eviction where reconfiguring the number of eviction threads could result in a segfault. refs SERVER-17293
• Significant bug fixes and performance enhancements to the logging subsystem including:
  • Avoid yielding excessively to avoid CPU overhead when there are many active sessions. refs #1610
  • The log close thread needs to wait for outstanding writes. #1571
  • Create a new utility thread to close and fsync log files. #1560
  • Ensure that log files are closed in sequence. #1555
  • Ensure that log file create appears atomic. #1482
  • Fix a race between connection close and switching log files that could lead to a new log file being in an undefined state. #1480
• Added support for advanced options to the WiredTiger verify command line tool.
• Fix a bug in our conflict detection algorithm, where we were failing to detect some write-write conflicts in no-overwrite cursors. refs SERVER-16351
• Significant bug fixes when writing pages to disk, including:
  • Stop double count the on-disk header when choosing split points. refs #1655
  • Fill the first and second pages as much as possible when splitting. refs #1282
  • Improve the algorithm for fitting large items onto pages when splitting. refs #1630 #1631
  • Fix a bug when using raw compression where we could overflow allocated memory. refs SERVER-16664
• Fix several cases where WT_SESSION::verify and WT_SESSION::salvage could return EBUSY unnecessarily. refs #1404 SERVER-16457
• Fix a bug where racing between discarding and updating a tree returned an error to the application. refs #1618 SERVER-17048
• Fix a bug where opening a statistics cursor in parallel with a checkpoint could lead to a deadlock. refs #1575 SERVER-16738
• Change the shared cache implementation to use cache read pressure rather than write pressure to determine how best to share memory (as checkpoints skew write pressure as a metric). refs #1569
• Fix a bug where a deadlock could occur if a checkpoint starts in parallel to compact operations. refs #1589 SERVER-16967
• Fix a bug in how we parse Huffman-encoding configuration settings during WT_SESSION::create. refs #1417 #1536
• Fix a bug where the custom extractor terminate callback was being made twice. refs #1503
• Add a new mode to the eviction server where it writes out some pages even though the eviction triggers have not yet been reached.
• Fix several issues reported by COVERITY static analysis tool.

WiredTiger release 2.5.0, 2014-12-24

The WiredTiger 2.5.0 release contains significant new features, API changes and many bug fixes.

Now that WiredTiger is part of MongoDB, we are tracking issues related to MongoDB usage of WiredTiger in the MongoDB JIRA system. Some entries in the changelog now reference JIRA tickets that can be found at:

http://jira.mongodb.org

New features and API changes:

• Add support for storing large values on-page in a btree rather than in an overflow item. This is useful for workloads that want to keep large items in cache - since WiredTiger overflow items are never cached. It is configured via new leaf_value_max configuration setting. This enhancement led to the deprecation of internal_item_max and leaf_item_max configuration settings, see upgrading documentation for further information. [#1282]
• Add support for compressing log files. When configured each compressible log record will be compressed. This is configure with the log=(compressor=X) configuration setting. See upgrading documentation for further information. [#1359]
• No longer return EBUSY when opening a bulk cursor, verifying or salvaging a database if a checkpoint is currently running. This allows applications to do these exclusive operations without shutting down the checkpoint server thread. [#1397] [#1404] SERVER-16236 SERVER-16457
• Add support for immutable indexes. [#1344]
• Added several new statistics, improved accuracy for some statistics tracking and simplified mechanism for querying a particular statistic. [#1505]
• Have the eviction server write out unnecessary pages prior to the cache reaching the configured eviction trigger size. This can reduce the amount of eviction application threads do when configured with a large cache.
• Several enhancements to managing how long we keep files open
• Revert a change in the 2.4.1 release that caused the WT_ROLLBACK (and deprecated WT_DEADLOCK) error return to map to different numeric values. Applications should ensure they are compiling against the same version of the wiredtiger.h header file as the library they link against, otherwise odd behavior will be experienced.
• Support setting configuration strings to "none" as being equivalent to an empty string in most cases. [#1417]
• Enhance the hot backup implementation to allow recovery to be run between incremental backups. [#1183]

Other significant changes:

• Improve performance of cursor open when there are many tables in a database. [#1391] [#1443]
• Reduce the impact checkpoints have on concurrent operations. This was done by changing how we lock tables. [#1391] [#1392]
• Improve performance when scanning a table that has many deleted items. SERVER-16247
• Fix a bug in checkpoint, where the metadata (turtle) file wasn't being synced on checkpoint. [#1383]
• Fix a bug where WiredTiger could accumulate memory during page splits and never free it. SERVER-16546
• Many enhancements and bug fixes for Windows.
• Fix a bug where a custom extractor terminate was being called twice. [#1503]
• Fix a bug where a race between closing a handle and checkpointing could lead to errors. [#1495] [#1497]
• Validate the block header checksum before we clear it - if the checksum field had been corrupted, we didn't notice. SERVER-16457
• Fix a bug in write conflict detection. Cursors configured with no-overwrite could sometimes not see update conflicts for deleted records. SERVER-16351
• Several bug fixes and performance improvements in LSM including:
  • Add support for custom collators in LSM trees. [#1361]
  • Fix a bug in LSM search_near, where it returned a deleted item. BF-694, BF-700
  • Improve background maintenance operations so that the cache does not get full unnecessarily.
  • Fix a bug that could lead to updates being written into old chunks. [#1432] [#1418]
  • Fix a bug in background merge that could skip updates. SERVER-16123
• Fix a bug when maintaining the cache, that could cause checkpoints to skip writing an update that should have been included. [#1419] SERVER-16336
• Fix a bug in WT_SESSION::drop, where failures generated error output even when force was specified. [#1436]
• Fix a bug in WiredTiger integer packing code when figuring out how much space is required for a value (it can shrink as numbers grow). SERVER-16118
• Several enhancements to the wtstats.py tool that generates graphs from standard WiredTiger statistics logs. [#1365]
• Fix a bug on OS X where fsync isn't sufficient to flush a file, use fcntl(F_FULLFSYNC) instead.
• Work around a bug in clang 3.5.0 compare and swap primitive. The __sync_bool_compare_and_swap version of the API in clang produces bad code for us with -O3 optimization enabled.

WiredTiger release 2.4.1, 2014-11-06

The WiredTiger 2.4.1 release contains several new features, many bug fixes and performance enhancements.

New features and API changes:

• Add new custom extractor functionality to WiredTiger indexes. Allowing an application to define mutated and/or multiple keys for indexes. [#1199]
• Add a new WT_SESSION::transaction_pinned_range method that allows users to identify when a session is keeping a transaction ID pinned for a long time. [#1314]
• Enhance statistics output so that keys are more clearly categorized. [#1313]
• Rename WT_DEADLOCK error return to WT_ROLLBACK. WiredTiger uses the return in cases other than traditional application deadlock. The old value is retained as an alias to maintain backward compatibility. [#1204]
• Increase the maximum configurable cache size to 100GB.

Other significant changes:

• Improve support for building on Windows platforms. [#1342]
• Fix a bug where WiredTiger could race closing handles. [#1336]
• Enhance performance when hot pages in cache are growing rapidly. [#1317]
• Fix a bug in recovery, where log files that are zero extended could result in some log records being skipped. [#1334]
• Updates to the Java API to improve documentation and exception handling. [#1295]
• Improve support for building on Oracle Solaris platform [#1329]
• Fix a bug where closing a handle could leave the tree in an inconsistent state on failure. [#1316]
• Several bug fixes and improvements to LSM including:
  • Improving algorithm for switching the in-memory chunk.
  • Fixing a bug related to dropping obsolete chunks. [#1304]
• Fix a bug in schema level operations (table create, drop, etc). If there was an explicit transaction running when the operation was performed that was subsequently rolled back the object could be left in an inconsistent state.
• Several enhancements to cache management when there are long running transactions present.

WiredTiger release 2.4.0, 2014-10-15

The WiredTiger 2.4.0 release contains significant new features, API changes and many bug fixes.

New features and API changes:

• Cursors keep their position across transaction boundaries. That is WT_SESSION::begin_transaction and WT_SESSION::commit_transaction no longer reset cursors. [#1181]
• Change cursor behavior so that when an operation returns WT_NOTFOUND, the cursor is now left pointing to the original key/value pair. [#1209]
• Initial support for building WiredTiger on Windows.
• Add ability to customize a collator for specific data sources or with application managed metadata. See upgrading documentation for more information. [#1165]
• Enhance extension mechanism in WiredTiger to support loading extensions from the application binary - not just a separate library. [#1174]
• Replace WT_SESSION::create "lsm=(merge_threads)" configuration option with wiredtiger_open "lsm_manager=(worker_thread_max)". See upgrading documentation for more information.
• Enhancements to the WiredTiger Python API build process. [#1188]
• Add ability to dump and load WiredTiger databases in JSON format. [#1154]
• Add ability to automatically checkpoint based on the volume of log records generated since the last checkpoint. This is enabled using the wiredtiger_open configuration option "checkpoint=(log_size=size)" [#1170]
• Enhance functionality allowing users to write content into the WiredTiger transaction log. [#1171][#1175]
• Enhance the WiredTiger HyperLevelDB implementation to support log replay. [#1106][#1155]

Other significant changes:

• Fix several bugs in the shared cache implementation. [#1180][#1176]
• Fix a bug where the public URI field in a cursor did not match the string passed to WT_SESSION::open_cursor. [#1235]
• Fix several bugs in salvage. [#1222][#1169]
• Several bug fixes and enhancements for WT_CONNECTION::reconfigure. [#1214][#1172]
• Fix several bugs in raw compression implementation, particularly for data that compresses extremely well. [#1191]
• Several bug fixes and enhancements to WiredTiger LevelDB interface.
• Switch default build from using adaptive pthread mutexes to default pthread mutexes.

WiredTiger release 2.3.1, 2014-08-14

The WiredTiger 2.3.1 release contains mainly performance enhancements and bug fixes.

Changes to the WiredTiger API:

• Fix a bug in WT_CURSOR::set_value that could lead to undefined behavior with some value formats.
• Make the asynchronous API generally available [#1139]
• Add log cursors for replay and verification. Make generated log record and operation types public. [#1106]
• Allow eviction worker threads to be started and stopped dynamically. Applications that use the eviction_workers configuration should see the upgrading documentation on how to use this feature. [#1116, #1143, #1158]

Other significant changes:

• Improve performance and reduce latency during checkpoints and LSM merges. Remove uses of the checkpoint lock other than serializing checkpoints: compact holds the schema lock, so it doesn't need to hold the checkpoint lock, the new WT_BTREE handle close lock prevents checkpoints from colliding with handle close, so LSM doesn't need the checkpoint lock either.
• Some minor cleanups, setting the internal session's name in a few places. [#1073]
• Grab the live lock when loading a checkpoint in diagnostic mode: that could race with a read. [#1102]
• Instead of keeping a list of file URIs for checkpoint to flush, open a handle and stash it. [#1114]
• Add a new OS-layer function __wt_fsync_async to flush a file without waiting for the results, call it from the Btree flush-leaves code so pages start flushing while we're working the rest of the checkpoint. [#1136, #1152]
• Wait for the handle flush lock when writing the leaf pages instead of returning EBUSY. [#1136]
• Add a wtperf page to the documentation, describe how to simulate workloads and view statistics. [#1147]
• Flag new structures not listed in PREDEFINE. [#1148]
• Return EBUSY if no async handles available and fix ex_async to look for it. [#1153]
• Fix some problems with navigation in the reference guide.
• Bump the number of slots for internal sessions: we have a lot more than 2 now. Add a test for session_max settings, make sure we add enough to account for at least the default internal sessions.
• Remove tcbench: we're no longer maintaining it.

WiredTiger release 2.3.0, 2014-07-29

The WiredTiger 2.3.0 release contains significant new features, performance enhancements and bug fixes. Significant changes are described below.

Changes to the WiredTiger API (see upgrading documentation for details):

• Add a LevelDB API implementation for WiredTiger. This includes support for stock LevelDB as well as Basho, HyperLevelDB and RocksDB versions of the API. To build the LevelDB API include –enable-leveldb in the configure command, to specify compatibility with an alternative LevelDB API use –enable-leveldb=[basho,hyper,rocksdb]. [#1028]
• Add ability to build some common extensions into the WiredTiger library. This means that the libraries for those extensions don't need to be dynamically loaded at runtime. Currently supported extensions are Snappy compression and zlib compression. The option can be enabled by passing –with-builtins=[snappy,zlib] to the configure command line.
• Add a new configuration to wiredtiger_open: statistics_log=(on_close=true), that causes a set of statistics to be logged on WT_CONNECTION::close. [#1086]
• Add a new configuration to wiredtiger_open: exclusive, that causes the open to fail if the database already exists.

Other significant changes:

• Performance improvement for high throughput workloads using multiple eviction threads. Performance of some workloads improves by over 15% [#1087]
• Significant performance optimizations for queries, giving up to 20% throughput improvement for in-memory query workloads. https://github.com/wiredtiger/wiredtiger/wiki/Query-throughput
• Fix an off-by-one bug that could lead to ENOMEM during commit with logging. [#1104][#1121]
• Allow bulk loads to multiple files to complete in parallel. [#1114][#1126]

WiredTiger release 2.2.1, 2014-06-24

The WiredTiger 2.2.1 release contains mainly performance enhancements and bug fixes. Significant changes are described below.

Changes to the WiredTiger API (see upgrading documentation for details):

• Change the order in which configuration setting mechanisms are applied by wiredtiger_open. [#1010][#1034]
• Split the global transaction_sync configuration into two parts: a sync method (dsync, fsync or none), and an enabled flag (false by default). [#1074]
• Add ability to sync with per transaction granularity. [#1074]
• Update WiredTiger Java API to throw WiredTigerException consistently. [#1011]
• Add ability to dump and load databases using JSON format. [#740][#1049]

Other significant changes:

• Various performance improvements to the main cursor search routine including reductions in how often we need to copy data and profiling based optimizations for tight search loops. [#1050][#1070]
• Fix a bug in recovery with missing files (e.g., after a hotbackup that raced with file creation). [#1042][#1045]
• Several bug fixes and performance enhancements related to LSM trees and snapshot isolation transactions. [#1057][#1060][#1075]
• Several performance tuning enhancements to LSM trees around locking, throttling and switching chunks. [#1051]
• Algorithmic improvements to LSM tree compact operation. It is now faster and more reliable. [#1063]
• Create a separate thread to manage open file handles - which means that:
  • Application threads are less likely to be responsible for closing handles
  • Multi threaded workloads don't open/close handles more often than necessary [#1018]

WiredTiger release 2.2.0, 2014-05-21

The WiredTiger 2.2.0 release contains new features, performance enhancements and bug fixes. Significant changes include:

Changes relevant for upgrading applications:

Update the table create API to disable prefix compression by default. Applications generally see better performance without prefix compression, choosing space saving over performance is up to the application. [#981]

Change the default leaf_page_max setting from 1MB to 32KB. Choosing a large default leaf_page_max led to poor performance in out of cache workloads.

Remove the --enable-debug option to configure. It is more standard to set CFLAGS="-g" variable instead.

Save the wiredtiger_open configuration when a database is created, so that settings like cache size, extensions and logging are set consistently by all subsequent users of the database.

Add an --enable-verbose option to configure. In order to access the verbose message functionality available as part of the wiredtiger_open and WT_CONNECTION::reconfigure APIs, it is necessary to pass the --enable-verbose option to configure.

Enhance the metadata cursor implementation (i.e: cursors created with a "metadata:" prefix) so that they can be used to inspect metadata for internal tables and now support altering the metadata. Add a new "read_only" flag to cursor configuration that defaults to false for metadata cursors.

Fix several bugs in raw compression, including one that could cause data corruption and some that triggered poor performance. [#984][#991][#1007][#1008][#1013]

Improve the performance of recovery - we no longer need to scan all log files looking for the last checkpoint.

Improve performance of read-only transactions, by deferring the allocation of transaction IDs. [#978]

Several bug fixes in hot backup related to log files, including:

• Always choose the right metadata version in the backup [#972]
• Don't require that hot backup copies log files in order [#976]
• Always copy log files before data files [#976]
• Fix a bug where recovery returned an error if the last log record was incomplete [#994]

Speed up checkpoints by doing a better job of skipping pages that can't contain changes that need to be included. [#954][#963][#1001]

Add ability to store zero length data items into LSM trees. [#540]

Add an asynchronous data access/manipulation API to WiredTiger. [#933]

Add the ability to configure multiple eviction server threads, to help with keeping space available in the cache. [#918]

Add the ability to reconfigure the checkpoint and statistics log servers. [#997][#1004]

Improve the performance of retrieving data for in cache workloads. [#970]

Improve the structure of the in-memory tree we are generating, by allowing internal pages to be split. This significantly improves query performance in some workloads. [#876]

Work around a bug in posix_fallocate on Linux, where it could corrupt already written data.

Add the ability to leak memory on connection close via new leak_memory option to WT_CONNECTION::close API. This allows for faster shutdown if a process is going to exit when the WiredTiger connection is closing.

Allow salvage to run on any table type.

WiredTiger release 2.1.2, 2014-03-27

The WiredTiger 2.1.2 release contains performance enhancements and bug fixes. Significant changes include:

Update the configuration settings for shared_cache to make the distinction between cache_size and shared_cache less confusing. See upgrading documentation for more information.

Various performance enhancements to improve the performance of checkpoints.

Fix a bug that could cause a hang with small caches under heavy load. [#894]

WiredTiger release 2.1.1, 2014-03-04

The WiredTiger 2.1.1 release contains new features, performance enhancements and bug fixes. Significant changes include:

Fix a bug where a page could be marked clean when it contained uncommitted changes. This bug could cause undefined behavior in transaction rollback under load.

Fix a bug with shared caches when rebalancing between connections.

Add a new public API to WiredTiger that provides the ability to parse WiredTiger compatible configuration strings. See the upgrading documentation for further information. [#873]

A number of performance enhancements to the LSM implementation, particularly for long running workloads.

A number of performance enhancements and bug fixes to cache eviction code.

Add an option to use direct I/O when reading from checkpoints. To enabled the functionality add "direct_io=[checkpoint]" to your wiredtiger_open configuration string. [#847]

WiredTiger release 2.1.0, 2014-02-04

The WiredTiger 2.1.0 release contains new features, performance enhancements and bug fixes. Significant changes include:

The WT_ITEM structure was changed so that the size field is a size_t rather than a uint32_t. See upgrading documentation for details.

A change to the compress_raw interface around repeating the call with more records. See upgrading documentation for details.

In LSM trees, the memory_page_max setting is ignored. The effective setting is double the chunk size. [#861][#859]

Add support for zlib compression. [#855] [#865]

Various enhancements to how WiredTiger generates tree structures in memory to help maintain consistent performance as table size grows. [#851]

Add support for Levyx Inc Helium as an external data source in WiredTiger [#849][#850]

Improve insert performance when a table contains many identical overflow items.

Various performance enhancements to btree searches. [#838][#839][#840]

Add support for newer versions of autoconf up to 1.14. [#599][#841]

Improve multi-threaded throughput of durable log writes, including changing the default wiredtiger_open transaction_sync configuration from dsync to fsync, see the upgrading documentation for further information. [#831][#832]

In the Python and Java APIs, automatically close handles to prevent invalid accesses by applications. [#649][#800][#830]

Various enhancements to the LSM merge algorithm, including improvements to how files are selected for merging, and throttling based on whether merges are keeping up (to limit write amplification). Made the minimum number of chunks chosen to merge configurable. [#817][#819][#822]

WiredTiger release 2.0.1, 2013-12-12

The WiredTiger 2.0.1 release contains major new features, numerous performance enhancements and bug fixes.

Significant changes include:

• WiredTiger now supports fine-grained durability via Write Ahead Logging (WAL). Logging is enabled with the "log=(enabled)" configuration string to wiredtiger_open. If the connection is not shut down cleanly and logging is enabled, WiredTiger will automatically run recovery the next time it is opened, rolling forward changes in the log until the last commit. [#605]
• Many enhancements to the LSM implementation to improve the throughput and reduce maximum operation latency including:
  • Algorithmic improvements when multiple merge threads are configured.
  • Improvements to bloom filter lookup speed.
  • Enhancements to internal cursor management, to reduce search overhead.
  • Prioritize switching to a new level 0 chunk in utility threads, to avoid application thread pauses.
  • More advanced logic in choosing when to create bloom filters.
• LSM specific WT_SESSION::create configuration option enhancements. Including:
  • Move existing options into their own group, and strip leading lsm_ prefix.
  • Add a new merge_max configuration option.
  • Update the default chunk_size to be 10MB.
  • Increase the default bloom filter bit and hash counts.
  • Clean up files left after interrupted merges. See the upgrading documentation for details. [#784, #785, #786, #802]
• WT_SESSION::compact can now be used to merge LSM trees into a small number of chunks on disk. [#792]
• Enhanced the Java API, so that when WiredTiger automatically closes a handle, the handle is automatically invalidated for the Java application. [#485]
• Add a script that can create an interactive web page to view statistics from a WiredTiger statistics log. Based on D3: http://d3js.org/
• Enhancements to the wtperf performance testing tool to add new features

WiredTiger release 1.6.6, 2013-11-19

The WiredTiger 1.6.6 release is a bugfix and performance tuning release.

This release of WiredTiger contains a database format change. Database files from previous releases will need to be upgraded.

A special note: the WiredTiger code base is now being regularly reviewed using the Coverity Static Analysis Verification Engine. We'd like to thank Coverity for their on-going support of Open Source projects like WiredTiger!

Significant changes include:

• Performance changes include: limiting operations done inside update serialization primitives, removing unnecessary memory barriers, replacing spinlocks with atomic instructions, padding structures to avoid false cache sharing, switching from per-file mutexes to per-page mutexes, pre-allocating structures to avoid memory allocation while holding mutexes, and using adaptive mutexes where available. [#707, #718, #719]
• A number of LSM stability and performance improvements: changes include better merge algorithms, reduced locking, and higher concurrency.
• A number of table compaction performance improvements, including changes allowing compaction to no longer read unnecessary file blocks into the cache, requires fewer passes over the file and support concurrent checkpoints and eviction. This change required an underlying file format change, see the upgrading documentation for details. [#756, #761]

• WiredTiger statistics have been significantly improved:

  Statistics logging has been changed to aggregate information from all open handles. [#709, #717]

  For performance reasons, statistics are now disabled by default, see the upgrading documentation for details. [#715]

  Statistics configuration has been changed so the connection and cursor configuration are consistent, with matching changes to the "wt stat" command-line utility; see the upgrading documentation for details.

• Update WT_EVENT_HANDLER interface to contain a new "handle close" interface and to pass a WT_SESSION handle into all callbacks, see the upgrading documentation for details. [#649]

  Add timestamp, process ID and thread ID to messages generated via WT_EVENT_HANDLER interface. [#753]

• WiredTiger eviction improvements, supporting larger data-to-cache size ratios. [#754]
• Various fixes for handling overflow records. [#726, #743]
• Overflow records are no longer tracked during bulk-loads, significantly increasing bulk-load performance for some data sets.

WiredTiger release 1.6.5, 2013-10-09

This is primarily a bugfix and performance tuning release. The main changes are:

• Change the default statistics_fast configuration from false to true.
• Change WT_CURSOR::insert to not hold a position. [#673]
• Disallow WT_SESSION::compact operations on LSM trees.
• The 'sync' setting to wiredtiger_open has been renamed 'checkpoint_sync'.
• Add a "metadata:" cursor type. [#660]
• Fix race in the cache's dirty byte tracking. [#635, #699]
• Fix a bug scanning through a memory-mapped file with overflow items. [#701]
• Use hardware checksum instructions when available. [#582, #702]
• Several bug fixes related to tracking active transaction IDs and detection of obsolete updates with high concurrency workloads. [#639, #643, #657, #683]
• Fix several bugs in LSM including races on shutdown and Bloom filter creation. [#686, #687, #688].
• Fix a bug in LSM where we were not including Bloom filter files in backups. [#684]
• Optimize the LSM throttle and merge algorithms. [#676]
• Make hot backups work concurrently with files being bulk-loaded. [#570, #653]
• Add full support for snapshot isolation to LSM: only switch LSM chunks if all changes are globally visible and detect conflicts between transactions across file switches. [#629]

WiredTiger release 1.6.4, 2013-08-20

This is primarily a bugfix and performance tuning release. The main changes are:

• Make prefix compression of keys conditional on the amount of space saved. A database format change was required for this enhancement. See upgrading documentation for details. [#624]
• The default behavior of the wt utility's load command has been changed to overwrite existing data.
• Add a WT_SESSION::create prefix_compression_min configuration option with a default value of 4. [#624] and [#624]
• Fix "make install" of Python API. [#598]
• Require platform support for atomic read/write of 64 bit values. [#553]
• Support transaction semantics for custom data source implementations. Enhance Memrata data source to support transactions.
• Changes to the wtperf testing tool related to how configuration options are specified.
• Enhance cursor key/value memory management to be more efficient, consistent, and have stricter checking of inputs and outputs.
• Increase the likelihood of being able to evict hot pages. [#604]
• Reference on-page keys instead of copying them to allocated memory. This saves space in the cache and overhead when reading pages into cache. [#592] and [#600]
• Add a btree search optimization that skips matching prefixes. [#595]
• Turn off Huffman encoding for keys on row-store internal pages. [#592]
• Add concurrent logging infrastructure that will be used to support write ahead logging in a future release.

WiredTiger release 1.6.3, 2013-07-12

This is a bugfix and performance tuning release. The main changes are:

• Change the default cursor overwrite configuration so that it is consistent across all data sources. This change may alter the behavior of existing applications without triggering any compilation or runtime warnings. See the upgrade documentation for details. [#512]
• Require platform support for 64 bit atomic operations. [#553]

WiredTiger release 1.6.2, 2013-06-18

This is a bugfix and performance tuning release. The main changes are:

• Fix a race in the WiredTiger pseudo random number generator that was leading to poor distribution of numbers.
• Change the default compression configuration to "uncompressed".
• Fix a race between checkpoints and LSM that could result in a crash. [#543]
• Add an option to output version information at runtime. Configure by including "verbose=[version]" in the wiredtiger_open connection configuration string. [#564]
• Add a configurable prefix to error messages. [#527]
• Add two new extension APIs, one to return a transaction ID, one to return if a transaction ID is visible to the current transaction.
• Add standard metadata functions to the extension API and make extension data sources responsible for their own metadata entries.
• Add a new extension function __wt_ext_config_strget that returns the configuration value from a single string.

WiredTiger release 1.6.1, 2013-05-31

This is a bugfix and performance tuning release. The main changes are:

• Fix the compress_raw API so that it uses platform independent types. See the upgrade guide for further information. [#561]
• Add an explicit enable setting to shared_cache configuration. See the upgrade guide for further information.
• Fix several bugs in hot backup, including race conditions between backup and table drop (and other schema level operations). [#556] [#557]
• Allow any data source type for indices as well as column groups. [#545]
• Preload btree internal pages into file system cache when opening a table.
• Change the default allocation size to 4KB so that DIRECT_IO with 4KB blocks works. [#547]
• Fix some bugs related to tracking the oldest active transaction. [#552]
• Fix a bug in the extension API when using multiple databases.
• Disallow named checkpoints on LSM trees - they aren't supported. [#546]
• Fix support for custom collators with LSM trees. [#544]
• Build fixes for gcc 4.1.2.

See the upgrade documentation for details of API changes that may require altering existing applications.

WiredTiger release 1.6.0, 2013-05-16

This release contains new features, bug fixes and performance improvements. The significant changes are highlighted below:

• Fix a bug where configuring direct I/O could cause checksum errors at runtime. NOTE: database file format change. [#526]
• Fix a race that allowed checkpoints to be deleted while hot backups are running. [#515]
• Scale to events per second in graphs generated from statistics log output. [#518]
• Changes to reduce the latency of LSM operations.
• Add a new terminate callback to extension interfaces that is called when the WiredTiger connection is closed. [#530]
• Various optimizations and bug fixes to cache management and eviction code.
• Update various statistics.
• Fix a bug where using a combination of read-committed and snapshot transactions could result in inconsistent values being returned. [#539]
• Fix a bug where using LSM trees with compression enabled could result in an invalid system call. [#535]
• Enhance statistics logging so that it can dump "lsm:" statistics.

See the upgrade documentation for information about database format changes in this release.

WiredTiger release 1.5.3, 2013-04-26

This release contains some major new features along with numerous bug fixes and performance improvements. The significant changes are highlighted below:

• Enhance the extension data source API to facilitate implementation of new data stores in WiredTiger.
• Add support for the STEC / Memrata KVS data source.
• Add a Berkeley DB data source via the WiredTiger extension API.
• Various enhancements to cache eviction management. Mostly to avoid stalls in application threads.
• Fixes to shared cache pool implementation, so resources are more aggressively reallocated.
• Add new statistics.
• Implement automatic insert throttling in LSM - enabled by default.
• Configuration strings are now case sensitive.
• Enhance LSM merge algorithms to be more efficient as trees grow very large.

See the upgrade documentation for details of API changes that may require altering existing applications.

WiredTiger release 1.5.2, 2013-03-28

This is a bugfix release. The main changes are:

[#493] Fix get_key/value in the Java API for complex cursors.

• Fix a leak in eviction detected by valgrind.
• Stop trying to cache the oldest reader: we only use it for eviction and only update it when required.
• Track cursor creation in the statistics (creating a cursor per operation isn't a good idea).

WiredTiger release 1.5.1, 2013-03-25

This is a bugfix and performance tuning release. The main changes are:

• Fix several bugs in LSM:
  • the logic for setting the "no eviction" flag on LSM chunks was reversed, causing unnecessary eviction once the cache became full;
  • calling session.checkpoint while writing to an LSM tree could confuse the logic around switching to new chunks; and
  • fix a possible NULL pointer indirection when switching chunks.
• Make WT_ASSERT a no-op when not in DIAGNOSTIC mode.
• Panic if we find a block on the wrong list, that's not something we can recover from.
• If a page is reconciled (causing it's on-disk blocks to be freed and potentially recycled), and then a subsequent collapse of a stack of split-merge pages replaces that page with a page that has not yet been reconciled, we can potentially free the same blocks twice. The fix is to clear the page's WT_REF.addr field at the time we free the blocks, so future reconciliations will ignore the original disk blocks.
• Fix a bug in the dump utility that allowed index URIs.
• Tweak merge to build better trees with random insert workloads.
• Don't use a stale value for the oldest reader transaction ID.
• Track the size of the WT_REF array in internal pages (including WT_ADDRs). Also add an estimate of per-allocation overhead.
• Fix a bug where URIs containing absolute paths were not being parsed correctly.
• Add a RMW insert mode to wtbench.

[#427] Improve cleanup after a failed wiredtiger_open call.

[#484] Don't allow true/false values in config strings where integers are expected.

[#486] Move the cache full check for autocommit transactions out of the rollback path (since we don't reset cursors there), to after we close a cursor.

[#488] Fix an assertion failure if we try to do eviction without ever having done an update.

WiredTiger release 1.5.0, 2013-03-14

This release contains some major new features along with numerous bug fixes and performance improvements. The significant changes are highlighted below:

• Add a Java API.
• Create a thread to do automatic checkpoints, configured by passing "checkpoint=(wait=X)" to wiredtiger_open.
• Add support for periodically logging statistics to a file and a tool to generate graphs based on those logs. Configured by passing "statistics_log=(wait=X)" to wiredtiger_open.
• Several changes to minimize the impact of checkpoints on other threads.
• When reading from checkpoints, use mmap by default.
• Enhance eviction so that internal pages take up less space.
• Add maximum filesystem buffer cache settings to wiredtiger_open called "os_cache_max" and "os_cache_dirty_max". After doing the specified amount of reads or writes, WiredTiger will call fadvise and/or sync_file_range to drop pages from the filesystem cache. This is an alternative to direct I/O with less impact on performance.
• Make run-time statistics optional, defaulted to "off".
• Change how we detect if shared cache is used. It used to rely on a name, now it will be used if the shared_cache configuration option is included.
• Add the ability to specify a per-connection reserved size for cache pools. Ensure cache pool reconfiguration is honored quickly.
• Rework hazard pointer coupling during cursor walks to be more efficient.
• Add a cache_eviction_walk statistic to track the pages we walk and a cache_eviction_force statistic to track the count of pages queued for forced eviction.
• Fixes to reduce the number of operations on shared data that were causing bottlenecks in read only workloads.
• Add streaming pack / unpack to the API.
• Add some basic reconciliation stats to the connection stats.
• In LSM, keep trying to switch if there is an error: it may be transient.
• Minor clean up and enhancement for the reconciliation statistics, add a set of compression statistics, both to the data-source statistics.
• Compaction cannot run at the same time as a checkpoint: the problem is that checkpoints review page reconciliation information and checkpoints update page reconciliation information. Lock out checkpoints while compaction is running.

WiredTiger release 1.4.2, 2013-01-14

[#387] Fast-path "S" and "u" formats in cursor.get_key and cursor.get_value.

[#407] Allow non-conflicting updates to complete concurrently.

[#418] Add code in to prioritize eviction of pages that are larger than a certain threshold. This avoids taking a performance hit when a huge page needs to be reconciled. Add a new memory_max_page configuration option.

[#419] If a page splits, it potentially creates a merge-split internal page and we potentially walk that page during fast-delete. The WT_REF.addr field doesn't point to a cell in that case and we'll drop core.

[#424] Add clarification wording for boolean configuration strings.

[#425] Perform checkpoints in the calling thread, don't block eviction: when evicting in a file that is being checkpointed, only evict clean pages. Also Do compaction in the calling thread instead of interrupting the eviction thread to do the work.

[#426] Fixes for automake 1.3.x. Allow examples to run in parallel: give each a unique home directory.

Make the tree build without HAVE_VERBOSE.

Fix some issues with LSM rename and add a Python test.

Track when cursors refer to memory returned by WiredTiger, copy it if required before dropping hazard pointers that might be protecting it.

Verify shouldn't ever modify the file – don't bother checking for dirty pages, just discard everything.

When rolling forward to resolve key prefix compression, don't copy the key, we only need a reference to it, should speed up tables with lots of key prefix compression.

Requested changes for the WT_COMPRESSOR::compress_raw method API: pass in the configured object's page size as a convenience, and if WT_COMPRESSOR::pre_size is set, use it to determine the size of the destination buffer, rather than using the object's page size as the maximum needed.

WiredTiger release 1.4.1, 2012-12-12

This is a bugfix, cleanup and performance tuning release. The significant changes are highlighted below:

[215] Add a __wt_panic function that shuts down all of the WiredTiger APIs. Also add a new error return WT_PANIC which means there has been an error in the WiredTiger engine, and it should be restarted.

[409] Fix a bug populating column groups with complex schema. Also allow empty column lists in projection cursors.

[150] Add description of how to do index-only searches to the documentation.

[392] Move examples/c/ex_test_perf.c to bench/wtperf.

[322] Add support for statistics on schema-level objects i.e tables, column groups, indices.

• Enhance statistics, including changing the name of some statistics.
• Fix a bug in the eviction server that could cause it to abort, leaving the system unusable.

WiredTiger release 1.4.0, 2012-12-03

This release adds several major new features, a number of performance improvements and bug fixes. The significant changes are outlined below:

New features and API changes:

[242] Track the percentage of cache that is dirty, trigger eviction to bound it. This can be used to bound how much data checkpoints write.

[324] Add support for WT_COMPRESS::compress_raw, which lets the compression routine select how many rows are included in each disk block.

[381] Add statistics to track read and write amplification (application data size versus I/O size)

• Add a trigger configuration option to WT_SESSION::compact API.
• Make WT_SESSION::create's checksum configuration 3-state: on, off, or uncompressed blocks only.

Bug fixes:

• Fix build issues on Solaris.
• Fix a bug calculating the generation of an LSM merge.
• Fix WiredTiger dump and load for tables.
• Fix a memory leak in checkpoints.
• Improve accuracy of cache memory tracking with overflow items.

WiredTiger release 1.3.8, 2012-11-22

This release improves the performance of LSM trees, changes how statistics are reported and adds a shared cache implementation:

New features and API changes:

[232] Add a "size of checkpoint" statistic.

• Add a shared cache pool implementation. Manages a single cache among multiple databases within a process.
• Merge statistics from file and LSM sources into a "data source" statistic structure. Rename and regroup some shared statistics. Add a helper to the Python API to lookup in a cursor in a simple expression.
• Add support for sub groups of options in configuration strings.

Performance tuning for LSM trees:

• Don't try to merge with a chunk that is much larger than a small chunk.
• After an LSM merge, fault in some pages before the new tree goes live to avoid stalling application threads.
• Don't automatically fail inserts if the write generation check fails: compare keys instead.
• Switch the LSM tree lock to a read/write lock, so cursors can read the state of the tree in parallel.

Bug fixes:

• Fix a bug where we could write past the end of a buffer after it was grown.

WiredTiger release 1.3.7, 2012-11-09

This release fixes a bug and improves performance with Bloom filters:

• Drop any old Bloom filter before creating a new one – we may have been interrupted in between creating it and updating the metadata. Write the metadata after creating missing Bloom filters.
• Use a separate thread for creation of Bloom filters for the newest, unmerged LSM chunks.
• Changes to the ex_test_perf example: change the default configuration to 4KB pages and disable prefix compression. Change the "-i" command line option to be a simple count of records to insert. Clean up error handling and add option to populate using multiple threads.
• Clarify the docs for the default buffer_alignment setting.

WiredTiger release 1.3.6, 2012-11-06

This is a bugfix and performance tuning release. The changes are as follows:

• Rename the WiredTiger installed modules to libwiredtiger_XXX. Don't install the nop and reverse collator modules.
• Replace test/format's bzip configuration string with compression, which can take one of four arguments (none, bzip, ext, snappy), change format to run snappy compression if the library is available.
• Rename the builtin block compressor names from "bzip2_compress" to "bzip2", and from "snappy_compress" to "snappy".
• Support multiple LSM merge threads with the "lsm_merge_threads" config key. Use IDs rather than array index to mark the start chunk in a merge, in case we race with another thread.
• Cache the hash values used for Bloom filter lookups, rather than hashing for each Bloom filter in an LSM tree.
• Only switch trees in an LSM cursor if the primary chunk is on disk.
• Add a per-btree cache priority, currently only used to make it more likely for Bloom filter pages to stay in cache.
• Only evict pages with read generations in the bottom quarter of the range we see. Fix a 32-bit wrapping bug in assigning read generations.
• For update-only LSM cursors, only open a cursor in the primary chunk.
• LSM: Report errors from the checkpoint thread.
• LSM: only save a Bloom URI in the metadata after it is successfully created.
• LSM: Create missing Bloom filters when reading from an LSM tree if "lsm_bloom_newest"is set.
• LSM: Include all of the chosen chunks in a merge. Only pin the current chunk in an LSM cursor if it is writeable.

WiredTiger release 1.3.5, 2012-10-26

This is a bugfix and performance tuning release. The changes are as follows:

[#370] Document that applications are responsible for figuring out their upgrade path if they might swap out compression engines.

[#371] When a single session was used to reconcile multiple btrees, one of which had dictionaries configured and one of which didn't, we failed to clear the dictionary when starting page reconciliation. Be consistent, never use anything other than the btree handle's configuration to decide if we're using a dictionary in a reconciliation run.

[#372] Fix several potential integer overflow bugs.

[#373] Fix a bug where calls that performed an operation on multiple objects (such as creating a table that implicitly creates a column group) could leave the metadata incomplete if a process exited without calling WT_CONNECTION::close. Hold the schema lock while opening tables. Fixes the error "cannot be opened until all column groups are created" message when create calls race with open_cursor.

[#374] Fix a race that caused crashes when using the Python API with multi-threaded code.

[#375] Fix a bug in __wt_cond_wait - so that it returns after timeout expires.

• Protect the list of LSM trees with the schema lock to avoid races during create.
• Update ex_test_perf to output statistics during populate and improve timing accuracy.
• Skew eviction in favor of leaf pages - which improves read-only performance for large LSM trees.
• Hold the LSM tree lock while gathering statistics.
• Fix a bug in bulk load of bitmap files.
• Fix a related bug in the bloom code that uses bitmap stores.
• Don't attempt to drop the first chunk of an LSM tree before creating it.
• Instead of entering a fake key cell after the last cell on the page just in case the page ends with a key cell which has no value, use the end of the page to detect that case.
• Cache cursor key/value formats in Python, to save a native call from every get_key/value.
• Don't sync the directory after open if the global "sync" flag is false.
• Fix a race for LSM trees that could happen if two threads race to open a cursor and drop the LSM tree.

WiredTiger release 1.3.4, 2012-10-19

This release includes several important new features, including:

• support for online compaction of files;
• support for tables, column groups and indices that use LSM trees for storage; and
• improved statistics and configuration for LSM trees and Bloom filters.

In addition, there are some significant performance improvements and bug fixes. The full list of changes is:

[#248] Add support for online compaction.

[#310] Fixed a bug where overflow blocks could be accessed by a long-running reader after they had been freed in a checkpoint.

[#358] Allocate checkpoint blocks from the live system's list of available blocks rather than always extending the file.

[#361] Sync the directory after creating a file: this is apparently required for durability on Linux, according to the Linux fsync man page.

[#362] Don't check if a page is on the avail or discard lists if we're salvaging the file, that is okay.

[#363] Remove obsolete code dealing with forced eviction.

[#366] Fake checkpoints may have the delete flag set, ignore them when rolling checkpoints forward.

[#367] All metadata reads should ignore the application's transactional context.

[#369] Support LSM as a data source for tables, column groups and indices.

• Add tuning options for LSM bloom filters, including controlling whether the oldest level in the tree has a Bloom filter, whether newly-created (level 0) files have Bloom filters, and passing arbitrary file configuration for Bloom filters.
• Add a merge generation to LSM chunks. Add a statistic that reports the highest merge generation in a tree.
• Add a new LSM statistic tracking searches that could benefit from bloom filters.
• Enable LSM statistics in the "wt stat" utility.
• Interrupt LSM merge operations, rather than waiting on close.
• Wait for a while before looking for LSM major merges, in case merges catch up with inserts.
• Fix LSM index searches. The main issue was LSM search_near was not always returning the closest key to the search key, which calling code expects. It now tries hard to find the smallest cursor larger than the search key, and only if no larger record exists does it return the largest record smaller than the search key.
• Reset any old cursor position before an LSM search. This limits hazard references in an LSM search to a single chunk.
• Fix a memory leak in an error path in Bloom filters.
• Tweak the search loops in hazard_{set,clear} in favor of last-in-first-out ordering.
• If there are many files open, some hotter than others, walk more files looking for pages to evict.
• Don't stop evicting until we reach the target, have eviction wake up periodically regardless of whether the application signals it. This latter requires a "timed condition wait" operation.
• Tweaks to file handle flags for out-of-cache read performance on Linux (disable read-ahead and access time updates).
• Replace the WT_SESSION::dumpfile method with configuration strings to WT_SESSION::verify.
• Fix a bug where we weren't skipping unnecessary default checkpoints because we weren't handling the generational number included in the internal checkpoint name.
• Add a "force" configuration flag to WT_SESSION::checkpoint, object compaction needs it because the work it wants done is done by the block manager.
• Make compact and checkpoint operate on a table's indices.
• When doing a page truncate, lock down the page before we unpack the on-page cell – it's possible the page could be instantiated, modified and reconciled while we're sleeping, in which case the WT_REF.addr field would no longer point on-page.

WiredTiger release 1.3.3, 2012-10-11

This is a bugfix and performance tuning release, primarily related to LSM trees. The changes are as follows:

[#350] Checkpoint the metadata after successful schema-level operations. Otherwise, if process exits without closing the connection or running a checkpoint, created objects exist but there is no record in the metadata.

[#351] Don't put checkpoint extent blocks on the available list, blocks on it are considered for truncation; they have to go on the "checkpoint available" list.

• Choose LSM merges based on a measure of efficiency (levels collapsed per record), rather than simply choosing a minor or a major merge. Tweak the merge heuristic so we don't end up with runs of smaller chunks in the middle of the tree.
• Add a connection-wide flag to disable LSM merges.
• Don't create Bloom filters for the oldest chunk in the system. Add the ability to disable Bloom filters entirely.
• Fix fast-path for bit values in WT_CURSOR::set_value.
• Clean up allocation of LSM chunk IDs.
• Update bloom_get so that it doesn't hold a cursor position.
• Respect the page size for fixed-length column stores, remembering there are 8 bits per byte.
• Support bulk loading a bitmap into a fixed-length column store, update Bloom filter code to use this.
• Add an example program, ex_test_perf, to demonstrate basic LSM usage.
• Add a new statistics cursor type "statistics:lsm". Update ex_stat.c to demonstrate usage.
• Add a statistics_fast flag to file statistics cursors. Update LSM statistics so that they aggregate some cache statistics. Add ability to open a statistics cursor on a checkpoint.
• Walk a constant number of pages for LRU eviction.
• Move the cache full check to after an update operation completes, when it is no longer holding hazard references. This improves behavior with small caches.

WiredTiger release 1.3.2, 2012-10-03

This is a bugfix and performance tuning release, primarily related to LSM trees. The changes are as follows:

• Implement minor merges for LSM trees, prefer them to major merges.
• Update hazard references, so the active array grows as needed. Change the default hazard_max to 1000.
• Abort transactions if the cache is so full that they cannot make progress.
• Fix a bug where verify could crash if an empty checkpoint exists.
• Make the maximum number of chunks for merges configurable, rather than deriving a value from the number of hazard references available.
• Switch to an atomic add to allocate transaction IDs. This fixes a subtle race before where two threads could temporarily have the same ID in the global state table. If one of the threads timed out and the other thread committed its transaction with that ID, the commit would not become visible immediately. This could lead to deadlock errors in workloads that are logically conflict-free.
• Have auto-commit transactions retry deadlocks. This requires that we keep the user's key and value in the cursor.
• Simplify the code handling updated records in variable-length column-store reconciliation.
• Never wait for eviction when holding the schema lock. This avoids deadlocks between opening a column store file and taking a checkpoint.
• Take care with the loop termination when walking files for eviction. We were making one extra call into __wt_tree_walk, which would leave a leaf page in the WT_REF_EVICT_WALK state, unable to be evicted. In some workloads, including LSM loads, we could end up with many files all consisting of a single leaf page, none of which could be evicted.
• Pause updates when the cache is full.
• In files marked as "out of cache", don't wait for eviction when reading a page.
• Fix the record count calculation for minor merges. This was leading to no Bloom filter being created for minor merges after running for some time, leading to merges taking increasingly long to complete.
• Only sleep in the LSM checkpoint thread if no work is done.
• Add sanity check of cache size to LSM open.

[#338] Create fake checkpoints until an object is modified, so that a checkpoint between the cursor create and the bulk load doesn't make it impossible to do a bulk-load on the cursor.

WiredTiger release 1.3.1, 2012-09-25

This is a bugfix release, primarily related to LSM trees. The changes are as follows:

[#309] Implement auto-commit of transactions at the API. As well as ensuring the atomicity of complex operations, this change simplified code that simulated auto-commit internally and fixed a number of bugs.

[#321] Bulk-cursors no longer block checkpoints. We can't write files that are being bulk-loaded, so change checkpoint to create checkpoints in the metadata that, if accessed, look like empty files.

Tighten down the requirements for bulk-load, the only thing that can be bulk-loaded now is a newly created tree, not any empty file.

[#329] Add dictionary support to variable-length column store objects. Support large row-store reconciliation dictionaries: add a skiplist as the indexing mechanism.

[#333] Fix a leak of the in-memory transaction log structure and the LSM data source handle.

[#334] Fix a memory leak where a page's replacement address wasn't being freed.

• Check that LSM trees are not configured as column stores.
• Fix a race when starting the LSM worker thread. It was possible for the thread to exit immediately if it started fast enough.
• Two fixes for LSM, one to ensure that cursors read from a checkpoint if one is available. The other to reduce the number of empty chunks that can be created initially.
• Fix a bug that disabled bloom filters.
• The configure script checks for Python support in SWIG.
• If a drop operation fails to acquire all of the handle locks it needs, make sure it releases the primary handle lock.
• Fix a number of other minor bugs and memory leaks.

WiredTiger release 1.3.0, 2012-09-17

This release contains a number of major new features, including:

• support for LSM trees with Bloom filters;
• support for hot backups; and
• support for fast truncation of files.

In addition, there are some critical bug fixes. We recommend that all users upgrade. Here is the full list of changes:

[#143] Implement random record lookups.

[#168] Add support for LSM trees.

[#168] Add support for Bloom filters in LSM trees.

[#198] Handle page-generation wraparound.

[#236] Implement hot backups.

[#244] Index cursors for column-store objects may not be created using the record number as the index key.

[#247] Add a fast-path for WT_SESSION::truncate that avoids reading most data to be deleted.

[#259] Performance hack for cursor open: don't parse the configuration strings for a default value if the application didn't specify a configuration string.

[#262] Disable dump on child cursors: only the top-level cursor is wrapped in a dump cursor.

[#266] Deal with new / dropped indices in __wt_schema_open_index.

[#269] Checkpoint handles must not be open when they are overwritten.

[#271] Add support for a reserved checkpoint name "WiredTigerCheckpoint" that opens the object's last checkpoint.

[#271] Add the ability to access unnamed checkpoints.

[#274] Change cursor.equals to return a standard error value and store the cursor equality result in a separate argument.

[#275] If exclusive handle is required for an operation and it is not available, fail immediately: don't block.

[#276] Fix methods that return integer parameters from Python. This includes cursor.equals and cursor.search_near.

[#277] Acquire the schema lock when creating the metadata file. We're single-threaded, so it isn't protecting against anything, but the handle management code expects to have the schema lock.

[#279] Some optimizations for __wt_config_gets_defno. Specifically, if we're dealing with a simple stack of config strings, just parse the application string rather than the full list of defaults.

[#279] Split the description string into a set of structures, to reduce the number of string comparisons and manipulation that's required.

[#282] Remove the cursor.reconfigure method, and replace it with documentation showing how to "reconfigure" cursors using the session.open_cursor method to duplicate them with different configuration strings.

[#284] Fix for a hazard reference race, where page eviction races with the creation of the hazard reference, we have to check the pointer itself as well as the state of the pointer.

[#285] We can clear the tree's modified flag on checkpoint, as long as the checkpoint writes all modifications. Clear the tree's modified flag before we start the checkpoint, but reset it as necessary if reconciliation is unable to write all of the changes in a page.

[#287] Fix __wt_config_check to handle overlapping config values correctly.

[#289] Add support for read-committed isolation, make it the default. Add a session-level "isolation" setting.

[#294] If txn_commit fails, document the transaction was rolled-back.

[#295] Expand the documentation on using cursors without explicit transactions.

[#300] Include all changes whenever closing a file, don't check for visibility. If updates are skipped while evicting a page, give up.

[#305] Have "wt dump" fail more gracefully if the object doesn't exist.

[#310] When freeing a tracked address in reconciliation, clear it to avoid freeing the same address again on error.

[#314] Replace cursor.equals with cursor.compare

[#319] Clear the bulk_load_ok flag when closing handles.

• Add an "ancient transaction" statistic so we can find out if they're actually occurring in the field.
• Add an "was object ever modified" flag to the btree handle, and use it to avoid writing read-only objects during internal checkpoints, issue
• Add per-connection statistics counters for transaction checkpoint, begin, commit and rollback. Add per-btree statistics counters for update conflicts.
• Another fixed-length column-store implicit record fix: if the earliest row in the object is row 10, and it's on an append list, we still must return rows 1-9, they've been implicitly created.
• Bulk cursors: disallow cursor.{equals,next,prev,reset,search, search_near,update,remove}; only close and insert are supported.
• Change session.truncate to support any cursor position for range truncation, not just keys that are known to exist.
• Checkpoint has to flush the metadata file, but only after it's flushed all of the other files.
• Discard obsolete WT_UPDATE structures during updates.
• Document that duplicated cursors are positioned at the same point as the cursor that was duplicated.
• Fix a (very unlikely) deadlock at startup, if an application issues a checkpoint before the eviction server has managed to open its session.
• Fix a core dump if we verify a file that's corrupted such that we are unable to load any checkpoints at all, and the per-checkpoint bit map is never set.
• If a page selected for eviction cannot be freed because it has some recent updates, try instead to free memory by trimming old updates.
• If a thread fails to evict a page, try to bump its snapshot. This avoids the common case of read-committed threads getting stuck because one thread falls behind (e.g., because we can't evict during a checkpoint).
• If an exclusive table create fails, return EEXIST.
• If we try to remove a file that doesn't exist, don't complain, return success.
• If we're repeatedly taking a checkpoint with the same name, skip the work for read-only objects.
• Instead of flagging the empty tree's leaf page empty as part of creating an empty tree in memory, set the page as modified (to force reconciliation); if the leaf page is still empty at that time, then we'll figure it out during that reconciliation. This fixes a memory leak where the leaf page of a empty tree wasn't being freed.
• It's not unreasonable to open a cursor on a non-existent table, don't complain, just return not-found.
• Move dist/RELEASE to the top level of the tree.
• Optimization: don't repeatedly look up btree handles for schema operations.
• Return keys from all operations: don't keep pointing to the application's key.
• Update btree usage of 64 bitstring implementation, so it's cleaner.
• Update the bitstring implementation to use 64 bit length strings.
• Updates performed without an active transaction should become visible with the current transaction ID.
• Upgrade to doxygen 1.8.x
• Use a real snapshot transaction for checkpoints. Otherwise, the snapshot can be updated in between checkpointing multiple files (when updating the metadata).

WiredTiger release 1.2.2, 2012-06-20

This is a bugfix release. The changes are as follows:

• Defer making free pages available until the end of a checkpoint, in case there is a failure after processing some files.
• When checking the value of the "isolation" key, don't assume it is nul terminated. This bug could cause transactions to run with incorrect isolation.
• Fix two bugs with snapshot isolation:
  1. reset the isolation level when the transaction completes;
  2. when checking visibility, check item's ID against the maximum snapshot ID (not the transaction's ID).

WiredTiger release 1.2.1, 2012-06-15

This is a bugfix release. The changes are as follows:

• Avoid a deadlock between eviction and checkpoint on the connection spinlock.
• Allocate "desc" buffers in heap memory so that they are correctly aligned (fixes direct_io support on Linux).
• Initialize the snapshot-avail list after cleaning it out, else we'll try and print a NULL pointer in VERBOSE mode.

WiredTiger release 1.2.0, 2012-06-04

This release contains many bugfixes and improvements. The major changes are:

[#138] Add support for transactions with coarse-grained durability. Transactions provide atomicity guarantees and rollback, and uncommitted changes are never written to disk. There is no on-disk log, so committed changes only become durable when the next checkpoint completes. Checkpoints are implemented by creating transactionally-consistent snapshots within data files.

[#156] Fully support operations that make schema changes with multiple sessions open concurrently.

[#159] Disable internal page key suffix compression if a custom collator is configured. This avoids issues with collators that require complete keys.

[#167] Add support for durable snapshots within files. While a snapshot is active, the pages used by the snapshot will not be overwritten. If a file is accessed after a crash or application exit without calling WT_CONNECTION::close, any changes made after the last snapshot will be silently ignored.

[#214, #216] Fixes for forcing eviction with small caches.

WiredTiger release 1.1.5, 2012-04-26

Don't update a WT_REF after it has been unlocked.

Add an operation to set a flag atomically, use it to avoid racing on page flags.

Fix a race between sync and reading that could cause a segfault.

WiredTiger release 1.1.4, 2012-04-16

Check the versions of autoconf, automake and libtool to avoid failures when trying to build from the github tree with versions that are too old.

[#191] Create the schema table as part of creating the environment so that application threads don't race trying to create it later.

[#193] Split-merge pages have to be reconciled to mark their parents dirty

[#194] The dump utility should only output configuration that can be passed to WT_SESSION::create.

Eviction fixes for out-of-cache update workloads:

• Fix an unlikely bug where the EVICT_LRU flag was cleared when a page in the LRU queue was overwritten with itself during a walk. This led to an assertion failure when the page was later evicted.
• Clear all unused eviction queue entries while holding the lru_lock.
• Split WT_PAGE->flags so that there is no possibility of racing: (1) Move WT_PAGE_REC_* flags into WT_PAGE_MODIFY; (2) Use atomic operations to set and clear the remaining (2) page flags.

Move the test/format threads setting into the CONFIG file.

WiredTiger release 1.1.3, 2012-04-04

Fix the "exclusive" config for WT_SESSION::create. [#181]

1. Make it work for files within a single session.
2. Make it work for files across sessions.
3. Make other data sources consistent with files.

Fix an eviction bug introduced into 1.1.2: when evicting a page with children, remove the children from the LRU eviction queue. Reduce the impact of clearing a page from the LRU queue by marking pages on the queue with a flag (WT_PAGE_EVICT_LRU).

During an eviction walk, pin pages up to the root so there is no need to spin when attempting to lock a parent page. Use the EVICT_LRU page flag to avoid putting a page on the LRU queue multiple times.

Layer dump cursors on top of any cursor type.

Add a section on replacing the default system memory allocator to the tuning page.

Typo in usage method for "wt write".

Don't report range errors for config values that aren't well-formed integers.

WiredTiger release 1.1.2, 2012-03-20

Add public-domain copyright notices to the extension code.

test/format can now run multi-threaded, fixed two bugs it found: (1) When iterating backwards through a skiplist, we could race with an insert. (2) If eviction fails for a page, we have to assume that eviction has unlocked the reference.

Scan row-store leaf pages twice when reading to reduce the overhead of the index array.

Eviction race fixes: (1) Call __rec_review with WT_REFs: don't look at the page until we've checked the state. (2) Clear the eviction point if we hit it when discarding a child page, not just the parent.

Eviction tuning changes, particularly for read-only, out-of-cache workloads.

Only notify the eviction server if an application thread doesn't find any pages to evict, and then only once.

Only spin on the LRU lock if there might be pages in the LRU queue to evict.

Keep the current eviction point in memory and make the eviction walk run concurrent with LRU eviction.

Every test now has err/out captured, and it is checked to assure it is empty at the end of every test.

WiredTiger release 1.1.1, 2012-03-12

Default to a verbose build: that can be switched off by running configure --enable-silent-rules).

Account for all memory allocated when reading a page into cache. Total memory usage is now much closer to the cache size when using many small keys and values.

Have application threads trigger a retry forced page eviction rather than blocking eviction. This allows rec_evict.c to simply set the WT_REF state to WT_REF_MEM after all failures, and fixes a bug where pages on the forced eviction queue would end up with state WT_REF_MEM, meaning they could be chosen for eviction multiple times.

Grow existing scratch buffers in preference to allocating new ones.

Fix a race between threads reading in and then modifying a page.

Get rid of the pinned flag: it is no longer used.

Fix a race where btree files weren't completely closed before they could be re-opened. This behavior can be triggered by using a new session on every operation (see the new -S flag to the test/thread program). [#178]

When connections are closed, create a session and discard the btree handles. This fixes a long-standing bug in closing a connection: if for any reason there are btree handles still open, we need a real session handle to close them.

Really close btree handles: otherwise we can't safely remove or rename them. Fixes test failures in test_base02 (among others).

Wait for application threads in LRU eviction to drain before walking a file.

Fix a buffer size calculation when updating the root address of a file.

Documentation fix: 10% of 1MB is 100KB.

WiredTiger release 1.1.0, 2012-02-28

Add checks to the session.truncate method to ensure the start/stop cursors reference the same object and have been initialized.

Implement cursor duplication via WT_SESSION::open_cursor. [#161]

Switch to quiet builds by default.

Fix with automake version < 1.11, use foreign mode so that fewer top-level files are required.

If a session or connection method is about to return WT_NOTFOUND (some underlying object was not found), map it to ENOENT, only cursor methods return WT_NOTFOUND. [#163]

Save and restore session->btree in schema ops to simplify calling code. [#164]

Note the wiredtiger_open config string "multiprocess" is not yet supported.

Move "root:F" and "version:F" entries for files into the value for "file:F", so there is only a single record per file. [NOTE: SCHEMA CHANGE]

When parsing config strings, continue to the end of the string in case of repeated keys. [#124]

Don't require shared libraries unless Python is configured.

Add support for direct I/O, with the config "direct_io=(data,log)". Build with _GNU_SOURCE on Linux to enable O_DIRECT.

Don't keep the last page of column stores pinned: it prevented eviction of large trees created from scratch.

Allow application threads to evict pages from any tree: maintain a count of threads doing LRU in each tree and wait for activity to drain when closing.