* corrupt the database. Of course if your application code is known to
* be bug-free (...) then this is not an issue.
*
+ * If this is your first time using a transactional embedded key/value
+ * store, you may find the \ref starting page to be helpful.
+ *
* @section caveats_sec Caveats
* Troubleshooting the lock file, plus semaphores on BSD systems:
*
* access to locks and lock file. Exceptions: On read-only filesystems
* or with the #MDB_NOLOCK flag described under #mdb_env_open().
*
+ * - An LMDB configuration will often reserve considerable \b unused
+ * memory address space and maybe file size for future growth.
+ * This does not use actual memory or disk space, but users may need
+ * to understand the difference so they won't be scared off.
+ *
* - By default, in versions before 0.9.10, unused portions of the data
* file might receive garbage data from memory freed by other code.
* (This does not happen when using the #MDB_WRITEMAP flag.) As of
* transactions. Each transaction belongs to one thread. See below.
* The #MDB_NOTLS flag changes this for read-only transactions.
*
- * - Use an MDB_env* in the process which opened it, without fork()ing.
+ * - Use an MDB_env* in the process which opened it, not after fork().
*
* - 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.
+ * breaks fcntl() advisory locking. (It is OK to reopen it after
+ * fork() - exec*(), since the lockfile has FD_CLOEXEC set.)
*
* - Avoid long-lived transactions. Read transactions prevent
* reuse of pages freed by newer write transactions, thus the
*
* @author Howard Chu, Symas Corporation.
*
- * @copyright Copyright 2011-2015 Howard Chu, Symas Corp. All rights reserved.
+ * @copyright Copyright 2011-2018 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
/** Library minor version */
#define MDB_VERSION_MINOR 9
/** Library patch version */
-#define MDB_VERSION_PATCH 17
+#define MDB_VERSION_PATCH 22
/** 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 "November 30, 2015"
+#define MDB_VERSION_DATE "March 21, 2018"
/** A stringifier for the version info */
#define MDB_VERSTR(a,b,c,d) "LMDB " #a "." #b "." #c ": (" d ")"
MDB_PREV_NODUP, /**< Position at last data item of previous key */
MDB_SET, /**< Position at specified key */
MDB_SET_KEY, /**< Position at specified key, return key + data */
- MDB_SET_RANGE /**< Position at first key greater than or equal to specified key. */
+ MDB_SET_RANGE, /**< Position at first key greater than or equal to specified key. */
+ MDB_PREV_MULTIPLE /**< Position at previous page and return key and up to
+ a page of duplicate data items. Only for #MDB_DUPFIXED */
} MDB_cursor_op;
/** @defgroup errors Return Codes
* 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
+ * Use a writeable memory map unless MDB_RDONLY is set. This uses
+ * fewer mallocs but loses protection from application bugs
* like wild pointer writes and other bad updates into the database.
+ * This may be slightly faster for DBs that fit entirely in RAM, but
+ * is slower for DBs larger than RAM.
* Incompatible with nested transactions.
* Do not mix processes with and without MDB_WRITEMAP on the same
* environment. This can defeat durability (#mdb_env_sync etc).
* <li>#MDB_NOTLS
* Don't use Thread-Local Storage. Tie reader locktable slots to
* #MDB_txn objects instead of to threads. I.e. #mdb_txn_reset() keeps
- * the slot reseved for the #MDB_txn object. A thread may use parallel
+ * the slot reserved for the #MDB_txn object. A thread may use parallel
* read-only transactions. A read-only transaction may span threads if
* the user synchronizes its use. Applications that multiplex many
* user threads over individual OS threads need this option. Such an
* <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.
+ * Currently it fails if the environment has suffered a page leak.
* </ul>
* @return A non-zero error value on failure and 0 on success.
*/
int mdb_env_get_path(MDB_env *env, const char **path);
/** @brief Return the filedescriptor for the given environment.
+ *
+ * This function may be called after fork(), so the descriptor can be
+ * closed before exec*(). Other LMDB file descriptors have FD_CLOEXEC.
+ * (Until LMDB 0.9.18, only the lockfile had that.)
*
* @param[in] env An environment handle returned by #mdb_env_create()
* @param[out] fd Address of a mdb_filehandle_t to contain the descriptor.
* This flag may only be used in combination with #MDB_DUPSORT. This option
* tells the library that the data items for this database are all the same
* size, which allows further optimizations in storage and retrieval. When
- * all data items are the same size, the #MDB_GET_MULTIPLE and #MDB_NEXT_MULTIPLE
- * cursor operations may be used to retrieve multiple items at once.
+ * all data items are the same size, the #MDB_GET_MULTIPLE, #MDB_NEXT_MULTIPLE
+ * and #MDB_PREV_MULTIPLE cursor operations may be used to retrieve multiple
+ * items at once.
* <li>#MDB_INTEGERDUP
* This option specifies that duplicate data items are binary integers,
* similar to #MDB_INTEGERKEY keys.
* the database supports duplicates (#MDB_DUPSORT).
* <li>#MDB_RESERVE - reserve space for data of the given size, but
* don't copy the given data. Instead, return a pointer to the
- * reserved space, which the caller can fill in later. This saves
+ * 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. This flag
* must not be specified if the database was opened with #MDB_DUPSORT.
* <li>#MDB_APPEND - append the given key/data pair to the end of the
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