A connection to a WiredTiger database. More...

Public Member Functions
int	close (WT_CONNECTION connection, const char config)
	Close a connection. More...

int	reconfigure (WT_CONNECTION connection, const char config)
	Reconfigure a connection handle. More...

const char *	get_home (WT_CONNECTION *connection)
	The home directory of the connection. More...

int	configure_method (WT_CONNECTION connection, const char method, const char uri, const char config, const char type, const char check)
	Add configuration options for a method. More...

int	is_new (WT_CONNECTION *connection)
	Return if opening this handle created the database. More...

Async operation handles
int	async_flush (WT_CONNECTION *connection)
	Wait for all outstanding operations to complete. More...

int	async_new_op (WT_CONNECTION connection, const char uri, const char config, WT_ASYNC_CALLBACK callback, WT_ASYNC_OP **asyncopp)
	Return an async operation handle. More...

Session handles
int	open_session (WT_CONNECTION connection, WT_EVENT_HANDLER errhandler, const char config, WT_SESSION *sessionp)
	Open a session. More...

Extensions
int	load_extension (WT_CONNECTION connection, const char path, const char *config)
	Load an extension. More...

int	add_data_source (WT_CONNECTION connection, const char prefix, WT_DATA_SOURCE data_source, const char config)
	Add a custom data source. More...

int	add_collator (WT_CONNECTION connection, const char name, WT_COLLATOR collator, const char config)
	Add a custom collation function. More...

int	add_compressor (WT_CONNECTION connection, const char name, WT_COMPRESSOR compressor, const char config)
	Add a compression function. More...

int	add_extractor (WT_CONNECTION connection, const char name, WT_EXTRACTOR extractor, const char config)
	Add a custom extractor for index keys or column groups. More...

WT_EXTENSION_API *	get_extension_api (WT_CONNECTION *wt_conn)
	Return a reference to the WiredTiger extension functions. More...

Detailed Description

A connection to a WiredTiger database.

The connection may be opened within the same address space as the caller or accessed over a socket connection.

Most applications will open a single connection to a database for each process. The first process to open a connection to a database will access the database in its own address space. Subsequent connections (if allowed) will communicate with the first process over a socket connection to perform their operations.

Thread safety: A WT_CONNECTION handle may be shared between threads, see Multithreading for more information.

Examples:: ex_access.c, ex_async.c, ex_call_center.c, ex_config.c, ex_cursor.c, ex_extending.c, ex_extractor.c, ex_file.c, ex_hello.c, ex_log.c, ex_pack.c, ex_schema.c, ex_stat.c, and ex_thread.c.

Member Function Documentation

int WT_CONNECTION::add_collator	(	WT_CONNECTION *	connection,
		const char *	name,
		WT_COLLATOR *	collator,
		const char *	config
	)

Add a custom collation function.

The application must first implement the WT_COLLATOR interface and then register the implementation with WiredTiger:

static WT_COLLATOR my_collator = { my_compare, NULL, NULL };

ret = conn->add_collator(conn, "my_collator", &my_collator, NULL);

Parameters

connection	the connection handle
name	the name of the collation to be used in calls to WT_SESSION::create
collator	the application-supplied collation handler
config	Configuration string, see Configuration Strings. No values currently permitted.

Returns: zero on success and a non-zero error code on failure. See Error Returns for details.

Examples:: ex_extending.c.

int WT_CONNECTION::add_compressor	(	WT_CONNECTION *	connection,
		const char *	name,
		WT_COMPRESSOR *	compressor,
		const char *	config
	)

Add a compression function.

The application must first implement the WT_COMPRESSOR interface and then register the implementation with WiredTiger:

/* Local compressor structure. */
typedef struct {
        WT_COMPRESSOR compressor;               /* Must come first */
        WT_EXTENSION_API *wt_api;               /* Extension API */
        unsigned long nop_calls;                /* Count of calls */
} NOP_COMPRESSOR;

/*
 * wiredtiger_extension_init --
 *      A simple shared library compression example.
 */
int
wiredtiger_extension_init(WT_CONNECTION *connection, WT_CONFIG_ARG *config)
{
        NOP_COMPRESSOR *nop_compressor;
        (void)config;                           /* Unused parameters */
        if ((nop_compressor = calloc(1, sizeof(NOP_COMPRESSOR))) == NULL)
                return (errno);
        /*
         * Allocate a local compressor structure, with a WT_COMPRESSOR structure
         * as the first field, allowing us to treat references to either type of
         * structure as a reference to the other type.
         *
         * This could be simplified if only a single database is opened in the
         * application, we could use a static WT_COMPRESSOR structure, and a
         * static reference to the WT_EXTENSION_API methods, then we don't need
         * to allocate memory when the compressor is initialized or free it when
         * the compressor is terminated.  However, this approach is more general
         * purpose and supports multiple databases per application.
         */
        nop_compressor->compressor.compress = nop_compress;
        nop_compressor->compressor.compress_raw = NULL;
        nop_compressor->compressor.decompress = nop_decompress;
        nop_compressor->compressor.pre_size = nop_pre_size;
        nop_compressor->compressor.terminate = nop_terminate;
        nop_compressor->wt_api = connection->get_extension_api(connection);
                                                /* Load the compressor */
        return (connection->add_compressor(
            connection, "nop", (WT_COMPRESSOR *)nop_compressor, NULL));
}

Parameters

connection	the connection handle
name	the name of the compression function to be used in calls to WT_SESSION::create
compressor	the application-supplied compression handler
config	Configuration string, see Configuration Strings. No values currently permitted.

Returns: zero on success and a non-zero error code on failure. See Error Returns for details.

int WT_CONNECTION::add_data_source	(	WT_CONNECTION *	connection,
		const char *	prefix,
		WT_DATA_SOURCE *	data_source,
		const char *	config
	)

Add a custom data source.

See Custom Data Sources for more information.

The application must first implement the WT_DATA_SOURCE interface and then register the implementation with WiredTiger:

        static WT_DATA_SOURCE my_dsrc = {
                my_create,
                my_compact,
                my_drop,
                my_open_cursor,
                my_rename,
                my_salvage,
                my_truncate,
                my_range_truncate,
                my_verify,
                my_checkpoint,
                my_terminate
        };
        ret = conn->add_data_source(conn, "dsrc:", &my_dsrc, NULL);

Parameters

connection	the connection handle
prefix	the URI prefix for this data source, e.g., "file:"
data_source	the application-supplied implementation of WT_DATA_SOURCE to manage this data source.
config	Configuration string, see Configuration Strings. No values currently permitted.

Returns: zero on success and a non-zero error code on failure. See Error Returns for details.

int WT_CONNECTION::add_extractor	(	WT_CONNECTION *	connection,
		const char *	name,
		WT_EXTRACTOR *	extractor,
		const char *	config
	)

Add a custom extractor for index keys or column groups.

The application must first implement the WT_EXTRACTOR interface and then register the implementation with WiredTiger:

        static WT_EXTRACTOR my_extractor = {my_extract, NULL, NULL};
        ret = conn->add_extractor(conn, "my_extractor", &my_extractor, NULL);

Parameters

connection	the connection handle
name	the name of the extractor to be used in calls to WT_SESSION::create
extractor	the application-supplied extractor
config	Configuration string, see Configuration Strings. No values currently permitted.

Returns: zero on success and a non-zero error code on failure. See Error Returns for details.

Examples:: ex_extractor.c.

int WT_CONNECTION::async_flush ( WT_CONNECTION * connection )

Wait for all outstanding operations to complete.

/* Wait for all outstanding operations to complete. */

ret = conn->async_flush(conn);

Parameters

connection the connection handle

Returns: zero on success and a non-zero error code on failure. See Error Returns for details.

Examples:: ex_async.c.

int WT_CONNECTION::async_new_op	(	WT_CONNECTION *	connection,
		const char *	uri,
		const char *	config,
		WT_ASYNC_CALLBACK *	callback,
		WT_ASYNC_OP **	asyncopp
	)

Return an async operation handle.

                while ((ret = conn->async_new_op(conn,
                    "table:async", NULL, &ex_asynckeys.iface, &op)) != 0) {
                        /*
                         * If we used up all the handles, pause and retry to
                         * give the workers a chance to catch up.
                         */
                        fprintf(stderr,
                            "asynchronous operation handle not available\n");
                        if (ret == EBUSY)
                                sleep(1);
                        else
                                return (ret);
                }

Parameters

connection the connection handle

uri the connection handle

config

Configuration string, see Configuration Strings. Permitted values:

Name	Effect	Values
`append`	append the value as a new record, creating a new record number key; valid only for operations with record number keys.	a boolean flag; default `false`.
`overwrite`	configures whether the cursor's insert, update and remove methods check the existing state of the record. If `overwrite` is `false`, WT_CURSOR::insert fails with WT_DUPLICATE_KEY if the record exists, WT_CURSOR::update and WT_CURSOR::remove fail with WT_NOTFOUND if the record does not exist.	a boolean flag; default `true`.
`raw`	ignore the encodings for the key and value, manage data as if the formats were `"u"`. See Raw mode for details.	a boolean flag; default `false`.
`timeout`	maximum amount of time to allow for compact in seconds. The actual amount of time spent in compact may exceed the configured value. A value of zero disables the timeout.	an integer; default `1200`.

callback the operation callback

[out] asyncopp the new op handle

Returns: zero on success and a non-zero error code on failure. See Error Returns for details. If there are no available handles, EBUSY is returned.

Examples:: ex_async.c.

int WT_CONNECTION::close	(	WT_CONNECTION *	connection,
		const char *	config
	)

Close a connection.

Any open sessions will be closed.

ret = conn->close(conn, NULL);

Parameters

connection the connection handle

config

Configuration string, see Configuration Strings. Permitted values:

Name	Effect	Values
`leak_memory`	don't free memory during close.	a boolean flag; default `false`.

Returns: zero on success and a non-zero error code on failure. See Error Returns for details.

Examples:: ex_access.c, ex_async.c, ex_call_center.c, ex_config.c, ex_cursor.c, ex_extending.c, ex_extractor.c, ex_file.c, ex_hello.c, ex_log.c, ex_pack.c, ex_schema.c, ex_stat.c, and ex_thread.c.

int WT_CONNECTION::configure_method	(	WT_CONNECTION *	connection,
		const char *	method,
		const char *	uri,
		const char *	config,
		const char *	type,
		const char *	check
	)

Add configuration options for a method.

See Creating data-specific configuration strings for more information.

        /*
         * Applications opening a cursor for the data-source object "my_data"
         * have an additional configuration option "entries", which is an
         * integer type, defaults to 5, and must be an integer between 1 and 10.
         */
        ret = conn->configure_method(conn,
            "session.open_cursor",
            "my_data:", "entries=5", "int", "min=1,max=10");
        /*
         * Applications opening a cursor for the data-source object "my_data"
         * have an additional configuration option "devices", which is a list
         * of strings.
         */
        ret = conn->configure_method(conn,
            "session.open_cursor", "my_data:", "devices", "list", NULL);

Parameters

connection	the connection handle
method	the name of the method
uri	the object type or NULL for all object types
config	the additional configuration's name and default value
type	the additional configuration's type (must be one of `"boolean"\`, `"int"`, `"list"` or `"string"`)
check	the additional configuration check string, or NULL if none

Returns: zero on success and a non-zero error code on failure. See Error Returns for details.

WT_EXTENSION_API* WT_CONNECTION::get_extension_api ( WT_CONNECTION * wt_conn )

Return a reference to the WiredTiger extension functions.

#include <wiredtiger_ext.h>
static WT_EXTENSION_API *wt_api;
static void
my_data_source_init(WT_CONNECTION *connection)
{
        wt_api = connection->get_extension_api(connection);
}

Parameters

wt_conn the WT_CONNECTION handle

Returns: a reference to a WT_EXTENSION_API structure.

const char* WT_CONNECTION::get_home ( WT_CONNECTION * connection )

The home directory of the connection.

printf("The database home is %s\n", conn->get_home(conn));

Parameters

connection the connection handle

Returns: a pointer to a string naming the home directory

int WT_CONNECTION::is_new ( WT_CONNECTION * connection )

Return if opening this handle created the database.

        if (conn->is_new(conn)) {
                /* First time initialization. */
        }

Parameters

connection the connection handle

Returns: false (zero) if the connection existed before the call to wiredtiger_open, true (non-zero) if it was created by opening this handle.

int WT_CONNECTION::load_extension	(	WT_CONNECTION *	connection,
		const char *	path,
		const char *	config
	)

Load an extension.

        ret = conn->load_extension(conn, "my_extension.dll", NULL);
        ret = conn->load_extension(conn,
            "datasource/libdatasource.so",
            "config=[device=/dev/sd1,alignment=64]");

Parameters

connection the connection handle

path the filename of the extension module, or "local" to search the current application binary for the initialization function, see Extending WiredTiger for more details.

config

Configuration string, see Configuration Strings. Permitted values:

Name	Effect	Values
`config`	configuration string passed to the entry point of the extension as its WT_CONFIG_ARG argument.	a string; default empty.
`entry`	the entry point of the extension, called to initialize the extension when it is loaded. The signature of the function must match wiredtiger_extension_init.	a string; default `wiredtiger_extension_init`.
`terminate`	an optional function in the extension that is called before the extension is unloaded during WT_CONNECTION::close. The signature of the function must match wiredtiger_extension_terminate.	a string; default `wiredtiger_extension_terminate`.

Returns: zero on success and a non-zero error code on failure. See Error Returns for details.

int WT_CONNECTION::open_session	(	WT_CONNECTION *	connection,
		WT_EVENT_HANDLER *	errhandler,
		const char *	config,
		WT_SESSION **	sessionp
	)

Open a session.

WT_SESSION *session;

ret = conn->open_session(conn, NULL, NULL, &session);

Parameters

connection the connection handle

errhandler An error handler. If NULL, the connection's error handler is used

config

Configuration string, see Configuration Strings. Permitted values:

Name	Effect	Values
`isolation`	the default isolation level for operations in this session.	a string, chosen from the following options: `"read-uncommitted"`, `"read-committed"`, `"snapshot"`; default `read-committed`.

[out] sessionp the new session handle

Returns: zero on success and a non-zero error code on failure. See Error Returns for details.

Examples:: ex_access.c, ex_async.c, ex_call_center.c, ex_config.c, ex_cursor.c, ex_extending.c, ex_extractor.c, ex_file.c, ex_hello.c, ex_log.c, ex_pack.c, ex_schema.c, ex_stat.c, and ex_thread.c.

int WT_CONNECTION::reconfigure	(	WT_CONNECTION *	connection,
		const char *	config
	)

Reconfigure a connection handle.

ret = conn->reconfigure(conn, "eviction_target=75");

Parameters

connection the connection handle

config

Configuration string, see Configuration Strings. Permitted values:

Name	Effect	Values
`async = (`	asynchronous operations configuration options.	a set of related configuration options defined below.
`enabled`	enable asynchronous operation.	a boolean flag; default `false`.
`ops_max`	maximum number of expected simultaneous asynchronous operations.	an integer between 10 and 4096; default `1024`.
`threads`	the number of worker threads to service asynchronous requests.	an integer between 1 and 20; default `2`.
`)`
`cache_size`	maximum heap memory to allocate for the cache. A database should configure either a cache_size or a shared_cache not both.	an integer between 1MB and 10TB; default `100MB`.
`checkpoint = (`	periodically checkpoint the database.	a set of related configuration options defined below.
`log_size`	wait for this amount of log record bytes to be written to the log between each checkpoint. A database can configure both log_size and wait to set an upper bound for checkpoints; setting this value above 0 configures periodic checkpoints.	an integer between 0 and 2GB; default `0`.
`name`	the checkpoint name.	a string; default `"WiredTigerCheckpoint"`.
`wait`	seconds to wait between each checkpoint; setting this value above 0 configures periodic checkpoints.	an integer between 0 and 100000; default `0`.
`)`
`error_prefix`	prefix string for error messages.	a string; default empty.
`eviction = (`	eviction configuration options.	a set of related configuration options defined below.
`threads_max`	maximum number of threads WiredTiger will start to help evict pages from cache. The number of threads started will vary depending on the current eviction load.	an integer between 1 and 20; default `1`.
`threads_min`	minimum number of threads WiredTiger will start to help evict pages from cache. The number of threads currently running will vary depending on the current eviction load.	an integer between 1 and 20; default `1`.
`)`
`eviction_dirty_target`	continue evicting until the cache has less dirty memory than the value, as a percentage of the total cache size. Dirty pages will only be evicted if the cache is full enough to trigger eviction.	an integer between 10 and 99; default `80`.
`eviction_target`	continue evicting until the cache has less total memory than the value, as a percentage of the total cache size. Must be less than `eviction_trigger`.	an integer between 10 and 99; default `80`.
`eviction_trigger`	trigger eviction when the cache is using this much memory, as a percentage of the total cache size.	an integer between 10 and 99; default `95`.
`lsm_manager = (`	configure database wide options for LSM tree management.	a set of related configuration options defined below.
`merge`	merge LSM chunks where possible.	a boolean flag; default `true`.
`worker_thread_max`	Configure a set of threads to manage merging LSM trees in the database.	an integer between 3 and 20; default `4`.
`)`
`shared_cache = (`	shared cache configuration options. A database should configure either a cache_size or a shared_cache not both.	a set of related configuration options defined below.
`chunk`	the granularity that a shared cache is redistributed.	an integer between 1MB and 10TB; default `10MB`.
`name`	name of a cache that is shared between databases.	a string; default empty.
`reserve`	amount of cache this database is guaranteed to have available from the shared cache. This setting is per database. Defaults to the chunk size.	an integer; default `0`.
`size`	maximum memory to allocate for the shared cache. Setting this will update the value if one is already set.	an integer between 1MB and 10TB; default `500MB`.
`)`
`statistics`	Maintain database statistics, which may impact performance. Choosing "all" maintains all statistics regardless of cost, "fast" maintains a subset of statistics that are relatively inexpensive, "none" turns off all statistics. The "clear" configuration resets statistics after they are gathered, where appropriate (for example, a cache size statistic is not cleared, while the count of cursor insert operations will be cleared). When "clear" is configured for the database, gathered statistics are reset each time a statistics cursor is used to gather statistics, as well as each time statistics are logged using the `statistics_log` configuration. See Statistics for more information.	a list, with values chosen from the following options: `"all"`, `"fast"`, `"none"`, `"clear"`; default `none`.
`statistics_log = (`	log any statistics the database is configured to maintain, to a file. See Statistics for more information.	a set of related configuration options defined below.
`on_close`	log statistics on database close.	a boolean flag; default `false`.
`path`	the pathname to a file into which the log records are written, may contain ISO C standard strftime conversion specifications. If the value is not an absolute path name, the file is created relative to the database home.	a string; default `"WiredTigerStat.%d.%H"`.
`sources`	if non-empty, include statistics for the list of data source URIs, if they are open at the time of the statistics logging. The list may include URIs matching a single data source ("table:mytable"), or a URI matching all data sources of a particular type ("table:").	a list of strings; default empty.
`timestamp`	a timestamp prepended to each log record, may contain strftime conversion specifications.	a string; default `"%b %d %H:%M:%S"`.
`wait`	seconds to wait between each write of the log records.	an integer between 0 and 100000; default `0`.
`)`
`verbose`	enable messages for various events. Only available if WiredTiger is configured with –enable-verbose. Options are given as a list, such as `"verbose=[evictserver,read]"`.	a list, with values chosen from the following options: `"api"`, `"block"`, `"checkpoint"`, `"compact"`, `"evict"`, `"evictserver"`, `"fileops"`, `"log"`, `"lsm"`, `"metadata"`, `"mutex"`, `"overflow"`, `"read"`, `"reconcile"`, `"recovery"`, `"salvage"`, `"shared_cache"`, `"split"`, `"temporary"`, `"transaction"`, `"verify"`, `"version"`, `"write"`; default empty.

Returns: zero on success and a non-zero error code on failure. See Error Returns for details.

Public Member Functions

Detailed Description

Member Function Documentation