Name | Effect | Values |
allocation_size | the file unit allocation size, in bytes, must a power-of-two; smaller values decrease the file space required by overflow items, and the default value of 4KB is a good choice absent requirements from the operating system or storage device. | an integer between 512B and 128MB; default 4KB . |
block_allocation | configure block allocation. Permitted values are "first" or "best" ; the "first" configuration uses a first-available algorithm during block allocation, the "best" configuration uses a best-fit algorithm. | a string, chosen from the following options: "first" , "best" ; default best . |
block_compressor | configure a compressor for file blocks. Permitted values are empty (off) or "bzip2" , "snappy" or custom compression engine "name" created with WT_CONNECTION::add_compressor. See Compressors for more information. | a string; default empty. |
cache_resident | do not ever evict the object's pages; see Cache resident objects for more information. | a boolean flag; default false . |
checksum | configure block checksums; permitted values are on (checksum all blocks), off (checksum no blocks) and uncompresssed (checksum only blocks which are not compressed for any reason). The uncompressed setting is for applications which can rely on decompression to fail if a block has been corrupted. | a string, chosen from the following options: "on" , "off" , "uncompressed" ; default uncompressed . |
colgroups | comma-separated list of names of column groups. Each column group is stored separately, keyed by the primary key of the table. If no column groups are specified, all columns are stored together in a single file. All value columns in the table must appear in at least one column group. Each column group must be created with a separate call to WT_SESSION::create. | a list of strings; default empty. |
collator | configure custom collation for keys. Value must be a collator name created with WT_CONNECTION::add_collator. | a string; default empty. |
columns | list of the column names. Comma-separated list of the form (column[,...]) . For tables, the number of entries must match the total number of values in key_format and value_format . For colgroups and indices, all column names must appear in the list of columns for the table. | a list of strings; default empty. |
dictionary | the maximum number of unique values remembered in the Btree row-store leaf page value dictionary; see File formats and compression for more information. | an integer greater than or equal to 0; default 0 . |
exclusive | fail if the object exists. When false (the default), if the object exists, check that its settings match the specified configuration. | a boolean flag; default false . |
format | the file format. | a string, chosen from the following options: "btree" ; default btree . |
huffman_key | configure Huffman encoding for keys. Permitted values are empty (off), "english" , "utf8<file>" or "utf16<file>" . See Huffman Encoding for more information. | a string; default empty. |
huffman_value | configure Huffman encoding for values. Permitted values are empty (off), "english" , "utf8<file>" or "utf16<file>" . See Huffman Encoding for more information. | a string; default empty. |
internal_item_max | the largest key stored within an internal node, in bytes. If non-zero, any key larger than the specified size will be stored as an overflow item (which may require additional I/O to access). If zero, a default size is chosen that permits at least 8 keys per internal page. | an integer greater than or equal to 0; default 0 . |
internal_key_truncate | configure internal key truncation, discarding unnecessary trailing bytes on internal keys (ignored for custom collators). | a boolean flag; default true . |
internal_page_max | the maximum page size for internal nodes, in bytes; the size must be a multiple of the allocation size and is significant for applications wanting to avoid excessive L2 cache misses while searching the tree. The page maximum is the bytes of uncompressed data, that is, the limit is applied before any block compression is done. | an integer between 512B and 512MB; default 4KB . |
key_format | the format of the data packed into key items. See Format types for details. By default, the key_format is 'u' and applications use WT_ITEM structures to manipulate raw byte arrays. By default, records are stored in row-store files: keys of type 'r' are record numbers and records referenced by record number are stored in column-store files. | a format string; default u . |
leaf_item_max | the largest key or value stored within a leaf node, in bytes. If non-zero, any key or value larger than the specified size will be stored as an overflow item (which may require additional I/O to access). If zero, a default size is chosen that permits at least 4 key and value pairs per leaf page. | an integer greater than or equal to 0; default 0 . |
leaf_page_max | the maximum page size for leaf nodes, in bytes; the size must be a multiple of the allocation size, and is significant for applications wanting to maximize sequential data transfer from a storage device. The page maximum is the bytes of uncompressed data, that is, the limit is applied before any block compression is done. | an integer between 512B and 512MB; default 32KB . |
lsm = ( | options only relevant for LSM data sources. | a set of related configuration options defined below. |
auto_throttle | Throttle inserts into LSM trees if flushing to disk isn't keeping up. | a boolean flag; default true . |
bloom | create bloom filters on LSM tree chunks as they are merged. | a boolean flag; default true . |
bloom_bit_count | the number of bits used per item for LSM bloom filters. | an integer between 2 and 1000; default 16 . |
bloom_config | config string used when creating Bloom filter files, passed to WT_SESSION::create. | a string; default empty. |
bloom_hash_count | the number of hash values per item used for LSM bloom filters. | an integer between 2 and 100; default 8 . |
bloom_oldest | create a bloom filter on the oldest LSM tree chunk. Only supported if bloom filters are enabled. | a boolean flag; default false . |
chunk_max | the maximum size a single chunk can be. Chunks larger than this size are not considered for further merges. This is a soft limit, and chunks larger than this value can be created. Must be larger than chunk_size. | an integer between 100MB and 10TB; default 5GB . |
chunk_size | the maximum size of the in-memory chunk of an LSM tree. This limit is soft - it is possible for chunks to be temporarily larger than this value. This overrides the memory_page_max setting. | an integer between 512K and 500MB; default 10MB . |
merge_max | the maximum number of chunks to include in a merge operation. | an integer between 2 and 100; default 15 . |
merge_min | the minimum number of chunks to include in a merge operation. If set to 0 or 1 half the value of merge_max is used. | an integer no more than 100; default 0 . |
merge_threads | the number of threads to perform merge operations. | an integer between 1 and 10; default 2 . |
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memory_page_max | the maximum size a page can grow to in memory before being reconciled to disk. The specified size will be adjusted to a lower bound of 50 * leaf_page_max , and an upper bound of cache_size / 2 . This limit is soft - it is possible for pages to be temporarily larger than this value. This setting is ignored for LSM trees, see chunk_size . | an integer between 512B and 10TB; default 5MB . |
os_cache_dirty_max | maximum dirty system buffer cache usage, in bytes. If non-zero, schedule writes for dirty blocks belonging to this object in the system buffer cache after that many bytes from this object are written into the buffer cache. | an integer greater than or equal to 0; default 0 . |
os_cache_max | maximum system buffer cache usage, in bytes. If non-zero, evict object blocks from the system buffer cache after that many bytes from this object are read or written into the buffer cache. | an integer greater than or equal to 0; default 0 . |
prefix_compression | configure prefix compression on row-store leaf pages. | a boolean flag; default false . |
prefix_compression_min | minimum gain before prefix compression will be used on row-store leaf pages. | an integer greater than or equal to 0; default 4 . |
split_pct | the Btree page split size as a percentage of the maximum Btree page size, that is, when a Btree page is split, it will be split into smaller pages, where each page is the specified percentage of the maximum Btree page size. | an integer between 25 and 100; default 75 . |
type | set the type of data source used to store a column group, index or simple table. By default, a "file:" URI is derived from the object name. The type configuration can be used to switch to a different data source, such as LSM or an extension configured by the application. | a string; default file . |
value_format | the format of the data packed into value items. See Format types for details. By default, the value_format is 'u' and applications use a WT_ITEM structure to manipulate raw byte arrays. Value items of type 't' are bitfields, and when configured with record number type keys, will be stored using a fixed-length store. | a format string; default u . |