/** @file lmdb.h
* @brief Lightning memory-mapped database library
*
- * @mainpage Lightning Memory-Mapped Database Manager (MDB)
+ * @mainpage Lightning Memory-Mapped Database Manager (LMDB)
*
* @section intro_sec Introduction
- * MDB is a Btree-based database management library modeled loosely on the
+ * LMDB is a Btree-based database management library modeled loosely on the
* BerkeleyDB API, but much simplified. The entire database is exposed
* in a memory map, and all data fetches return data directly
* from the mapped memory, so no malloc's or memcpy's occur during
* readers, and readers don't block writers.
*
* Unlike other well-known database mechanisms which use either write-ahead
- * transaction logs or append-only data writes, MDB requires no maintenance
+ * transaction logs or append-only data writes, LMDB requires no maintenance
* during operation. Both write-ahead loggers and append-only databases
* require periodic checkpointing and/or compaction of their log or database
- * files otherwise they grow without bound. MDB tracks free pages within
+ * files otherwise they grow without bound. LMDB tracks free pages within
* the database and re-uses them for new write operations, so the database
* size does not grow without bound in normal use.
*
* stale locks can block further operation.
*
* Fix: Check for stale readers periodically, using the
- * #mdb_reader_check function or the mdb_stat tool. Or just
+ * #mdb_reader_check function or the \ref mdb_stat_1 "mdb_stat" tool. Or just
* make all programs using the database close it; the lockfile
* is always reset on first open of the environment.
*
*
* - Use an MDB_env* in the process which opened it, without fork()ing.
*
- * - Do not have open an MDB database twice in the same process at
+ * - Do not have open an LMDB database twice in the same process at
* the same time. Not even from a plain open() call - close()ing it
* breaks flock() advisory locking.
*
* - If you do that anyway, do a periodic check for stale readers. Or
* close the environment once in a while, so the lockfile can get reset.
*
- * - Do not use MDB databases on remote filesystems, even between
+ * - Do not use LMDB databases on remote filesystems, even between
* processes on the same host. This breaks flock() on some OSes,
* possibly memory map sync, and certainly sync between programs
* on different hosts.
*
* @author Howard Chu, Symas Corporation.
*
- * @copyright Copyright 2011-2014 Howard Chu, Symas Corp. All rights reserved.
+ * @copyright Copyright 2011-2015 Howard Chu, Symas Corp. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted only as authorized by the OpenLDAP
typedef int mdb_filehandle_t;
#endif
-/** @defgroup mdb MDB API
+/** @defgroup mdb LMDB API
* @{
* @brief OpenLDAP Lightning Memory-Mapped Database Manager
*/
/** Library minor version */
#define MDB_VERSION_MINOR 9
/** Library patch version */
-#define MDB_VERSION_PATCH 12
+#define MDB_VERSION_PATCH 14
/** Combine args a,b,c into a single integer for easy version comparisons */
#define MDB_VERINT(a,b,c) (((a) << 24) | ((b) << 16) | (c))
MDB_VERINT(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH)
/** The release date of this library version */
-#define MDB_VERSION_DATE "June 13, 2014"
+#define MDB_VERSION_DATE "September 20, 2014"
/** A stringifier for the version info */
-#define MDB_VERSTR(a,b,c,d) "MDB " #a "." #b "." #c ": (" d ")"
+#define MDB_VERSTR(a,b,c,d) "LMDB " #a "." #b "." #c ": (" d ")"
/** A helper for the stringifier macro */
#define MDB_VERFOO(a,b,c,d) MDB_VERSTR(a,b,c,d)
#define MDB_MULTIPLE 0x80000
/* @} */
+/** @defgroup mdb_copy Copy Flags
+ * @{
+ */
+/** Compacting copy: Omit free space from copy, and renumber all
+ * pages sequentially.
+ */
+#define MDB_CP_COMPACT 0x01
+/* @} */
+
/** @brief Cursor Get operations.
*
* This is the set of all operations for retrieving data
#define MDB_PANIC (-30795)
/** Environment version mismatch */
#define MDB_VERSION_MISMATCH (-30794)
- /** File is not a valid MDB file */
+ /** File is not a valid LMDB file */
#define MDB_INVALID (-30793)
/** Environment mapsize reached */
#define MDB_MAP_FULL (-30792)
#define MDB_BAD_TXN (-30782)
/** Unsupported size of key/DB name/data, or wrong DUPFIXED size */
#define MDB_BAD_VALSIZE (-30781)
-#define MDB_LAST_ERRCODE MDB_BAD_VALSIZE
+ /** The specified DBI was changed unexpectedly */
+#define MDB_BAD_DBI (-30780)
+ /** The last defined error code */
+#define MDB_LAST_ERRCODE MDB_BAD_DBI
/** @} */
/** @brief Statistics for a database in the environment */
unsigned int me_numreaders; /**< max reader slots used in the environment */
} MDB_envinfo;
- /** @brief Return the mdb library version information.
+ /** @brief Return the LMDB library version information.
*
* @param[out] major if non-NULL, the library major version number is copied here
* @param[out] minor if non-NULL, the library minor version number is copied here
* This function is a superset of the ANSI C X3.159-1989 (ANSI C) strerror(3)
* function. If the error code is greater than or equal to 0, then the string
* returned by the system function strerror(3) is returned. If the error code
- * is less than 0, an error string corresponding to the MDB library error is
- * returned. See @ref errors for a list of MDB-specific error codes.
+ * is less than 0, an error string corresponding to the LMDB library error is
+ * returned. See @ref errors for a list of LMDB-specific error codes.
* @param[in] err The error code
* @retval "error message" The description of the error
*/
char *mdb_strerror(int err);
- /** @brief Create an MDB environment handle.
+ /** @brief Create an LMDB environment handle.
*
* This function allocates memory for a #MDB_env structure. To release
* the allocated memory and discard the handle, call #mdb_env_close().
* how the operating system has allocated memory to shared libraries and other uses.
* The feature is highly experimental.
* <li>#MDB_NOSUBDIR
- * By default, MDB creates its environment in a directory whose
+ * By default, LMDB creates its environment in a directory whose
* pathname is given in \b path, and creates its data and lock files
* under that directory. With this option, \b path is used as-is for
* the database main data file. The database lock file is the \b path
* with "-lock" appended.
* <li>#MDB_RDONLY
* Open the environment in read-only mode. No write operations will be
- * allowed. MDB will still modify the lock file - except on read-only
- * filesystems, where MDB does not use locks.
+ * allowed. LMDB will still modify the lock file - except on read-only
+ * filesystems, where LMDB does not use locks.
* <li>#MDB_WRITEMAP
* Use a writeable memory map unless MDB_RDONLY is set. This is faster
* and uses fewer mallocs, but loses protection from application bugs
* like wild pointer writes and other bad updates into the database.
* Incompatible with nested transactions.
- * Processes with and without MDB_WRITEMAP on the same environment do
- * not cooperate well.
+ * Do not mix processes with and without MDB_WRITEMAP on the same
+ * environment. This can defeat durability (#mdb_env_sync etc).
* <li>#MDB_NOMETASYNC
* Flush system buffers to disk only once per transaction, omit the
* metadata flush. Defer that until the system flushes files to disk,
* the user synchronizes its use. Applications that multiplex many
* user threads over individual OS threads need this option. Such an
* application must also serialize the write transactions in an OS
- * thread, since MDB's write locking is unaware of the user threads.
+ * thread, since LMDB's write locking is unaware of the user threads.
* <li>#MDB_NOLOCK
* Don't do any locking. If concurrent access is anticipated, the
* caller must manage all concurrency itself. For proper operation
* @return A non-zero error value on failure and 0 on success. Some possible
* errors are:
* <ul>
- * <li>#MDB_VERSION_MISMATCH - the version of the MDB library doesn't match the
+ * <li>#MDB_VERSION_MISMATCH - the version of the LMDB library doesn't match the
* version that created the database environment.
* <li>#MDB_INVALID - the environment file headers are corrupted.
* <li>ENOENT - the directory specified by the path parameter doesn't exist.
*/
int mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode);
- /** @brief Copy an MDB environment to the specified path.
+ /** @brief Copy an LMDB environment to the specified path.
*
* This function may be used to make a backup of an existing environment.
* No lockfile is created, since it gets recreated at need.
*/
int mdb_env_copy(MDB_env *env, const char *path);
- /** @brief Copy an MDB environment to the specified file descriptor.
+ /** @brief Copy an LMDB environment to the specified file descriptor.
*
* This function may be used to make a backup of an existing environment.
* No lockfile is created, since it gets recreated at need.
*/
int mdb_env_copyfd(MDB_env *env, mdb_filehandle_t fd);
- /** @brief Return statistics about the MDB environment.
+ /** @brief Copy an LMDB environment to the specified path, with options.
+ *
+ * This function may be used to make a backup of an existing environment.
+ * No lockfile is created, since it gets recreated at need.
+ * @note This call can trigger significant file size growth if run in
+ * parallel with write transactions, because it employs a read-only
+ * transaction. See long-lived transactions under @ref caveats_sec.
+ * @param[in] env An environment handle returned by #mdb_env_create(). It
+ * must have already been opened successfully.
+ * @param[in] path The directory in which the copy will reside. This
+ * directory must already exist and be writable but must otherwise be
+ * empty.
+ * @param[in] flags Special options for this operation. This parameter
+ * must be set to 0 or by bitwise OR'ing together one or more of the
+ * values described here.
+ * <ul>
+ * <li>#MDB_CP_COMPACT - Perform compaction while copying: omit free
+ * pages and sequentially renumber all pages in output. This option
+ * consumes more CPU and runs more slowly than the default.
+ * </ul>
+ * @return A non-zero error value on failure and 0 on success.
+ */
+int mdb_env_copy2(MDB_env *env, const char *path, unsigned int flags);
+
+ /** @brief Copy an LMDB environment to the specified file descriptor,
+ * with options.
+ *
+ * This function may be used to make a backup of an existing environment.
+ * No lockfile is created, since it gets recreated at need. See
+ * #mdb_env_copy2() for further details.
+ * @note This call can trigger significant file size growth if run in
+ * parallel with write transactions, because it employs a read-only
+ * transaction. See long-lived transactions under @ref caveats_sec.
+ * @param[in] env An environment handle returned by #mdb_env_create(). It
+ * must have already been opened successfully.
+ * @param[in] fd The filedescriptor to write the copy to. It must
+ * have already been opened for Write access.
+ * @param[in] flags Special options for this operation.
+ * See #mdb_env_copy2() for options.
+ * @return A non-zero error value on failure and 0 on success.
+ */
+int mdb_env_copyfd2(MDB_env *env, mdb_filehandle_t fd, unsigned int flags);
+
+ /** @brief Return statistics about the LMDB environment.
*
* @param[in] env An environment handle returned by #mdb_env_create()
* @param[out] stat The address of an #MDB_stat structure
*/
int mdb_env_stat(MDB_env *env, MDB_stat *stat);
- /** @brief Return information about the MDB environment.
+ /** @brief Return information about the LMDB environment.
*
* @param[in] env An environment handle returned by #mdb_env_create()
* @param[out] stat The address of an #MDB_envinfo structure
/** @brief Flush the data buffers to disk.
*
* Data is always written to disk when #mdb_txn_commit() is called,
- * but the operating system may keep it buffered. MDB always flushes
+ * but the operating system may keep it buffered. LMDB always flushes
* the OS buffers upon commit as well, unless the environment was
- * opened with #MDB_NOSYNC or in part #MDB_NOMETASYNC.
+ * opened with #MDB_NOSYNC or in part #MDB_NOMETASYNC. This call is
+ * not valid if the environment was opened with #MDB_RDONLY.
* @param[in] env An environment handle returned by #mdb_env_create()
* @param[in] force If non-zero, force a synchronous flush. Otherwise
* if the environment has the #MDB_NOSYNC flag set the flushes
* @return A non-zero error value on failure and 0 on success. Some possible
* errors are:
* <ul>
+ * <li>EACCES - the environment is read-only.
* <li>EINVAL - an invalid parameter was specified.
* <li>EIO - an error occurred during synchronization.
* </ul>
* this process. Note that the library does not check for this condition,
* the caller must ensure it explicitly.
*
- * If the mapsize is changed by another process, #mdb_txn_begin() will
+ * The new size takes effect immediately for the current process but
+ * will not be persisted to any others until a write transaction has been
+ * committed by the current process. Also, only mapsize increases are
+ * persisted into the environment.
+ *
+ * If the mapsize is increased by another process, and data has grown
+ * beyond the range of the current mapsize, #mdb_txn_begin() will
* return #MDB_MAP_RESIZED. This function may be called with a size
* of zero to adopt the new size.
*
*/
void *mdb_env_get_userctx(MDB_env *env);
- /** @brief A callback function for most MDB assert() failures,
+ /** @brief A callback function for most LMDB assert() failures,
* called before printing the message and aborting.
*
* @param[in] env An environment handle returned by #mdb_env_create().
* After a successful commit the
* handle will reside in the shared environment, and may be used
* by other transactions. This function must not be called from
- * multiple concurrent transactions. A transaction that uses this function
- * must finish (either commit or abort) before any other transaction may
- * use this function.
+ * multiple concurrent transactions in the same process. A transaction
+ * that uses this function must finish (either commit or abort) before
+ * any other transaction in the process may use this function.
*
* To use named databases (with name != NULL), #mdb_env_set_maxdbs()
* must be called before opening the environment. Database names
* reserved space, which the caller can fill in later - before
* the next update operation or the transaction ends. This saves
* an extra memcpy if the data is being generated later.
- * MDB does nothing else with this memory, the caller is expected
+ * LMDB does nothing else with this memory, the caller is expected
* to modify all of the space requested.
* <li>#MDB_APPEND - append the given key/data pair to the end of the
- * database. No key comparisons are performed. This option allows
- * fast bulk loading when keys are already known to be in the
- * correct order. Loading unsorted keys with this flag will cause
- * data corruption.
+ * database. This option allows fast bulk loading when keys are
+ * already known to be in the correct order. Loading unsorted keys
+ * with this flag will cause a #MDB_KEYEXIST error.
* <li>#MDB_APPENDDUP - as above, but for sorted dup data.
* </ul>
* @return A non-zero error value on failure and 0 on success. Some possible
* <ul>
* <li>#MDB_CURRENT - replace the item at the current cursor position.
* The \b key parameter must still be provided, and must match it.
- * So must \b data if using sorted duplicates (#MDB_DUPSORT).
+ * If using sorted duplicates (#MDB_DUPSORT) the data item must still
+ * sort into the same place. This is intended to be used when the
+ * new data is the same size as the old. Otherwise it will simply
+ * perform a delete of the old record followed by an insert.
* <li>#MDB_NODUPDATA - enter the new key/data pair only if it does not
* already appear in the database. This flag may only be specified
* if the database was opened with #MDB_DUPSORT. The function will
#ifdef __cplusplus
}
#endif
+/** @page tools LMDB Command Line Tools
+ The following describes the command line tools that are available for LMDB.
+ \li \ref mdb_copy_1
+ \li \ref mdb_dump_1
+ \li \ref mdb_load_1
+ \li \ref mdb_stat_1
+*/
+
#endif /* _LMDB_H_ */
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