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9beea541e1
Also check xcursor instead of DUPSORT, it's slightly briefer.
1356 lines
60 KiB
C
1356 lines
60 KiB
C
/** @file lmdb.h
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* @brief Lightning memory-mapped database library
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*
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* @mainpage Lightning Memory-Mapped Database Manager (MDB)
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*
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* @section intro_sec Introduction
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* MDB is a Btree-based database management library modeled loosely on the
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* BerkeleyDB API, but much simplified. The entire database is exposed
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* in a memory map, and all data fetches return data directly
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* from the mapped memory, so no malloc's or memcpy's occur during
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* data fetches. As such, the library is extremely simple because it
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* requires no page caching layer of its own, and it is extremely high
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* performance and memory-efficient. It is also fully transactional with
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* full ACID semantics, and when the memory map is read-only, the
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* database integrity cannot be corrupted by stray pointer writes from
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* application code.
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*
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* The library is fully thread-aware and supports concurrent read/write
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* access from multiple processes and threads. Data pages use a copy-on-
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* write strategy so no active data pages are ever overwritten, which
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* also provides resistance to corruption and eliminates the need of any
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* special recovery procedures after a system crash. Writes are fully
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* serialized; only one write transaction may be active at a time, which
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* guarantees that writers can never deadlock. The database structure is
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* multi-versioned so readers run with no locks; writers cannot block
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* readers, and readers don't block writers.
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*
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* Unlike other well-known database mechanisms which use either write-ahead
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* transaction logs or append-only data writes, MDB requires no maintenance
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* during operation. Both write-ahead loggers and append-only databases
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* require periodic checkpointing and/or compaction of their log or database
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* files otherwise they grow without bound. MDB tracks free pages within
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* the database and re-uses them for new write operations, so the database
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* size does not grow without bound in normal use.
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*
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* The memory map can be used as a read-only or read-write map. It is
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* read-only by default as this provides total immunity to corruption.
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* Using read-write mode offers much higher write performance, but adds
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* the possibility for stray application writes thru pointers to silently
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* corrupt the database. Of course if your application code is known to
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* be bug-free (...) then this is not an issue.
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*
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* @section caveats_sec Caveats
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* Troubleshooting the lock file, plus semaphores on BSD systems:
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*
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* - A broken lockfile can cause sync issues.
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* Stale reader transactions left behind by an aborted program
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* cause further writes to grow the database quickly, and
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* stale locks can block further operation.
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*
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* Fix: Terminate all programs using the database, or make
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* them close it. Next database user will reset the lockfile.
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*
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* - On BSD systems or others configured with MDB_USE_POSIX_SEM,
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* startup can fail due to semaphores owned by another userid.
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*
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* Fix: Open and close the database as the user which owns the
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* semaphores (likely last user) or as root, while no other
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* process is using the database.
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*
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* Restrictions/caveats (in addition to those listed for some functions):
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*
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* - Only the database owner should normally use the database on
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* BSD systems or when otherwise configured with MDB_USE_POSIX_SEM.
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* Multiple users can cause startup to fail later, as noted above.
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*
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* - A thread can only use one transaction at a time, plus any child
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* transactions. Each transaction belongs to one thread. See below.
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* The #MDB_NOTLS flag changes this for read-only transactions.
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*
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* - Use an MDB_env* in the process which opened it, without fork()ing.
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*
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* - Do not have open an MDB database twice in the same process at
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* the same time. Not even from a plain open() call - close()ing it
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* breaks flock() advisory locking.
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*
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* - Avoid long-lived transactions. Read transactions prevent
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* reuse of pages freed by newer write transactions, thus the
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* database can grow quickly. Write transactions prevent
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* other write transactions, since writes are serialized.
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*
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* - Avoid suspending a process with active transactions. These
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* would then be "long-lived" as above. Also read transactions
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* suspended when writers commit could sometimes see wrong data.
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*
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* ...when several processes can use a database concurrently:
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*
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* - Avoid aborting a process with an active transaction.
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* The transaction becomes "long-lived" as above until the lockfile
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* is reset, since the process may not remove it from the lockfile.
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*
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* - If you do that anyway, close the environment once in a while,
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* so the lockfile can get reset.
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*
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* - Do not use MDB databases on remote filesystems, even between
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* processes on the same host. This breaks flock() on some OSes,
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* possibly memory map sync, and certainly sync between programs
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* on different hosts.
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*
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* - Opening a database can fail if another process is opening or
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* closing it at exactly the same time.
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*
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* @author Howard Chu, Symas Corporation.
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*
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* @copyright Copyright 2011-2013 Howard Chu, Symas Corp. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted only as authorized by the OpenLDAP
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* Public License.
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*
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* A copy of this license is available in the file LICENSE in the
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* top-level directory of the distribution or, alternatively, at
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* <http://www.OpenLDAP.org/license.html>.
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*
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* @par Derived From:
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* This code is derived from btree.c written by Martin Hedenfalk.
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*
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* Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#ifndef _LMDB_H_
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#define _LMDB_H_
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#include <sys/types.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/** Unix permissions for creating files, or dummy definition for Windows */
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#ifdef _MSC_VER
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typedef int mdb_mode_t;
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#else
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typedef mode_t mdb_mode_t;
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#endif
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/** An abstraction for a file handle.
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* On POSIX systems file handles are small integers. On Windows
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* they're opaque pointers.
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*/
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#ifdef _WIN32
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typedef void *mdb_filehandle_t;
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#else
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typedef int mdb_filehandle_t;
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#endif
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/** @defgroup mdb MDB API
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* @{
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* @brief OpenLDAP Lightning Memory-Mapped Database Manager
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*/
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/** @defgroup Version Version Macros
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* @{
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*/
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/** Library major version */
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#define MDB_VERSION_MAJOR 0
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/** Library minor version */
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#define MDB_VERSION_MINOR 9
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/** Library patch version */
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#define MDB_VERSION_PATCH 7
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/** Combine args a,b,c into a single integer for easy version comparisons */
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#define MDB_VERINT(a,b,c) (((a) << 24) | ((b) << 16) | (c))
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/** The full library version as a single integer */
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#define MDB_VERSION_FULL \
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MDB_VERINT(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH)
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/** The release date of this library version */
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#define MDB_VERSION_DATE "January 10, 2013"
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/** A stringifier for the version info */
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#define MDB_VERSTR(a,b,c,d) "MDB " #a "." #b "." #c ": (" d ")"
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/** A helper for the stringifier macro */
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#define MDB_VERFOO(a,b,c,d) MDB_VERSTR(a,b,c,d)
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/** The full library version as a C string */
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#define MDB_VERSION_STRING \
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MDB_VERFOO(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH,MDB_VERSION_DATE)
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/** @} */
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/** @brief Opaque structure for a database environment.
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*
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* A DB environment supports multiple databases, all residing in the same
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* shared-memory map.
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*/
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typedef struct MDB_env MDB_env;
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/** @brief Opaque structure for a transaction handle.
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*
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* All database operations require a transaction handle. Transactions may be
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* read-only or read-write.
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*/
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typedef struct MDB_txn MDB_txn;
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/** @brief A handle for an individual database in the DB environment. */
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typedef unsigned int MDB_dbi;
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/** @brief Opaque structure for navigating through a database */
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typedef struct MDB_cursor MDB_cursor;
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/** @brief Generic structure used for passing keys and data in and out
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* of the database.
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*
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* Key sizes must be between 1 and the liblmdb build-time constant
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* #MDB_MAXKEYSIZE inclusive. This currently defaults to 511. The
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* same applies to data sizes in databases with the #MDB_DUPSORT flag.
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* Other data items can in theory be from 0 to 0xffffffff bytes long.
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*
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* Values returned from the database are valid only until a subsequent
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* update operation, or the end of the transaction.
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*/
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typedef struct MDB_val {
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size_t mv_size; /**< size of the data item */
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void *mv_data; /**< address of the data item */
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} MDB_val;
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/** @brief A callback function used to compare two keys in a database */
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typedef int (MDB_cmp_func)(const MDB_val *a, const MDB_val *b);
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/** @brief A callback function used to relocate a position-dependent data item
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* in a fixed-address database.
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*
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* The \b newptr gives the item's desired address in
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* the memory map, and \b oldptr gives its previous address. The item's actual
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* data resides at the address in \b item. This callback is expected to walk
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* through the fields of the record in \b item and modify any
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* values based at the \b oldptr address to be relative to the \b newptr address.
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* @param[in,out] item The item that is to be relocated.
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* @param[in] oldptr The previous address.
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* @param[in] newptr The new address to relocate to.
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* @param[in] relctx An application-provided context, set by #mdb_set_relctx().
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* @todo This feature is currently unimplemented.
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*/
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typedef void (MDB_rel_func)(MDB_val *item, void *oldptr, void *newptr, void *relctx);
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/** @defgroup mdb_env Environment Flags
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*
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* Values do not overlap Database Flags.
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* @{
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*/
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/** mmap at a fixed address (experimental) */
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#define MDB_FIXEDMAP 0x01
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/** no environment directory */
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#define MDB_NOSUBDIR 0x4000
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/** don't fsync after commit */
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#define MDB_NOSYNC 0x10000
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/** read only */
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#define MDB_RDONLY 0x20000
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/** don't fsync metapage after commit */
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#define MDB_NOMETASYNC 0x40000
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/** use writable mmap */
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#define MDB_WRITEMAP 0x80000
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/** use asynchronous msync when MDB_WRITEMAP is used */
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#define MDB_MAPASYNC 0x100000
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/** tie reader locktable slots to #MDB_txn objects instead of to threads */
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#define MDB_NOTLS 0x200000
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/** @} */
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/** @defgroup mdb_dbi_open Database Flags
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*
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* Values do not overlap Environment Flags.
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* @{
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*/
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/** use reverse string keys */
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#define MDB_REVERSEKEY 0x02
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/** use sorted duplicates */
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#define MDB_DUPSORT 0x04
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/** numeric keys in native byte order.
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* The keys must all be of the same size. */
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#define MDB_INTEGERKEY 0x08
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/** with #MDB_DUPSORT, sorted dup items have fixed size */
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#define MDB_DUPFIXED 0x10
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/** with #MDB_DUPSORT, dups are numeric in native byte order */
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#define MDB_INTEGERDUP 0x20
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/** with #MDB_DUPSORT, use reverse string dups */
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#define MDB_REVERSEDUP 0x40
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/** create DB if not already existing */
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#define MDB_CREATE 0x40000
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/** @} */
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/** @defgroup mdb_put Write Flags
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* @{
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*/
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/** For put: Don't write if the key already exists. */
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#define MDB_NOOVERWRITE 0x10
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/** Only for #MDB_DUPSORT<br>
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* For put: don't write if the key and data pair already exist.<br>
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* For mdb_cursor_del: remove all duplicate data items.
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*/
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#define MDB_NODUPDATA 0x20
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/** For mdb_cursor_put: overwrite the current key/data pair */
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#define MDB_CURRENT 0x40
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/** For put: Just reserve space for data, don't copy it. Return a
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* pointer to the reserved space.
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*/
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#define MDB_RESERVE 0x10000
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/** Data is being appended, don't split full pages. */
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#define MDB_APPEND 0x20000
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/** Duplicate data is being appended, don't split full pages. */
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#define MDB_APPENDDUP 0x40000
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/** Store multiple data items in one call. Only for #MDB_DUPFIXED. */
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#define MDB_MULTIPLE 0x80000
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/* @} */
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/** @brief Cursor Get operations.
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*
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* This is the set of all operations for retrieving data
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* using a cursor.
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*/
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typedef enum MDB_cursor_op {
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MDB_FIRST, /**< Position at first key/data item */
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MDB_FIRST_DUP, /**< Position at first data item of current key.
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Only for #MDB_DUPSORT */
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MDB_GET_BOTH, /**< Position at key/data pair. Only for #MDB_DUPSORT */
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MDB_GET_BOTH_RANGE, /**< position at key, nearest data. Only for #MDB_DUPSORT */
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MDB_GET_CURRENT, /**< Return key/data at current cursor position */
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MDB_GET_MULTIPLE, /**< Return all the duplicate data items at the current
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cursor position. Only for #MDB_DUPFIXED */
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MDB_LAST, /**< Position at last key/data item */
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MDB_LAST_DUP, /**< Position at last data item of current key.
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Only for #MDB_DUPSORT */
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MDB_NEXT, /**< Position at next data item */
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MDB_NEXT_DUP, /**< Position at next data item of current key.
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Only for #MDB_DUPSORT */
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MDB_NEXT_MULTIPLE, /**< Return all duplicate data items at the next
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cursor position. Only for #MDB_DUPFIXED */
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MDB_NEXT_NODUP, /**< Position at first data item of next key */
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MDB_PREV, /**< Position at previous data item */
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MDB_PREV_DUP, /**< Position at previous data item of current key.
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Only for #MDB_DUPSORT */
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MDB_PREV_NODUP, /**< Position at last data item of previous key */
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MDB_SET, /**< Position at specified key */
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MDB_SET_KEY, /**< Position at specified key, return key + data */
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MDB_SET_RANGE /**< Position at first key greater than or equal to specified key. */
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} MDB_cursor_op;
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/** @defgroup errors Return Codes
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*
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* BerkeleyDB uses -30800 to -30999, we'll go under them
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* @{
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*/
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/** Successful result */
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#define MDB_SUCCESS 0
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/** key/data pair already exists */
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#define MDB_KEYEXIST (-30799)
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/** key/data pair not found (EOF) */
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#define MDB_NOTFOUND (-30798)
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/** Requested page not found - this usually indicates corruption */
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#define MDB_PAGE_NOTFOUND (-30797)
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/** Located page was wrong type */
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#define MDB_CORRUPTED (-30796)
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/** Update of meta page failed, probably I/O error */
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#define MDB_PANIC (-30795)
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/** Environment version mismatch */
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#define MDB_VERSION_MISMATCH (-30794)
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/** File is not a valid MDB file */
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#define MDB_INVALID (-30793)
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/** Environment mapsize reached */
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#define MDB_MAP_FULL (-30792)
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/** Environment maxdbs reached */
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#define MDB_DBS_FULL (-30791)
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/** Environment maxreaders reached */
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#define MDB_READERS_FULL (-30790)
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/** Too many TLS keys in use - Windows only */
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#define MDB_TLS_FULL (-30789)
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/** Txn has too many dirty pages */
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#define MDB_TXN_FULL (-30788)
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/** Cursor stack too deep - internal error */
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#define MDB_CURSOR_FULL (-30787)
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/** Page has not enough space - internal error */
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#define MDB_PAGE_FULL (-30786)
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/** Database contents grew beyond environment mapsize */
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#define MDB_MAP_RESIZED (-30785)
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/** MDB_INCOMPATIBLE: Operation and DB incompatible, or DB flags changed */
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#define MDB_INCOMPATIBLE (-30784)
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/** Invalid reuse of reader locktable slot */
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#define MDB_BAD_RSLOT (-30783)
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/** Transaction cannot recover - it must be aborted */
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#define MDB_BAD_TXN (-30782)
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/** Too big key/data, key is empty, or wrong DUPFIXED size */
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#define MDB_BAD_VALSIZE (-30781)
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#define MDB_LAST_ERRCODE MDB_BAD_VALSIZE
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/** @} */
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/** @brief Statistics for a database in the environment */
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typedef struct MDB_stat {
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unsigned int ms_psize; /**< Size of a database page.
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This is currently the same for all databases. */
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unsigned int ms_depth; /**< Depth (height) of the B-tree */
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size_t ms_branch_pages; /**< Number of internal (non-leaf) pages */
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size_t ms_leaf_pages; /**< Number of leaf pages */
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size_t ms_overflow_pages; /**< Number of overflow pages */
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size_t ms_entries; /**< Number of data items */
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} MDB_stat;
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/** @brief Information about the environment */
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typedef struct MDB_envinfo {
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void *me_mapaddr; /**< Address of map, if fixed */
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size_t me_mapsize; /**< Size of the data memory map */
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size_t me_last_pgno; /**< ID of the last used page */
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size_t me_last_txnid; /**< ID of the last committed transaction */
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unsigned int me_maxreaders; /**< max reader slots in the environment */
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unsigned int me_numreaders; /**< max reader slots used in the environment */
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} MDB_envinfo;
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/** @brief Return the mdb library version information.
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*
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* @param[out] major if non-NULL, the library major version number is copied here
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* @param[out] minor if non-NULL, the library minor version number is copied here
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* @param[out] patch if non-NULL, the library patch version number is copied here
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* @retval "version string" The library version as a string
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*/
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char *mdb_version(int *major, int *minor, int *patch);
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/** @brief Return a string describing a given error code.
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*
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* This function is a superset of the ANSI C X3.159-1989 (ANSI C) strerror(3)
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* function. If the error code is greater than or equal to 0, then the string
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* returned by the system function strerror(3) is returned. If the error code
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* is less than 0, an error string corresponding to the MDB library error is
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* returned. See @ref errors for a list of MDB-specific error codes.
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* @param[in] err The error code
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* @retval "error message" The description of the error
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*/
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char *mdb_strerror(int err);
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/** @brief Create an MDB environment handle.
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*
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* This function allocates memory for a #MDB_env structure. To release
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* the allocated memory and discard the handle, call #mdb_env_close().
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* Before the handle may be used, it must be opened using #mdb_env_open().
|
|
* Various other options may also need to be set before opening the handle,
|
|
* e.g. #mdb_env_set_mapsize(), #mdb_env_set_maxreaders(), #mdb_env_set_maxdbs(),
|
|
* depending on usage requirements.
|
|
* @param[out] env The address where the new handle will be stored
|
|
* @return A non-zero error value on failure and 0 on success.
|
|
*/
|
|
int mdb_env_create(MDB_env **env);
|
|
|
|
/** @brief Open an environment handle.
|
|
*
|
|
* If this function fails, #mdb_env_close() must be called to discard the #MDB_env handle.
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[in] path The directory in which the database files reside. This
|
|
* directory must already exist and be writable.
|
|
* @param[in] flags Special options for this environment. This parameter
|
|
* must be set to 0 or by bitwise OR'ing together one or more of the
|
|
* values described here.
|
|
* Flags set by mdb_env_set_flags() are also used.
|
|
* <ul>
|
|
* <li>#MDB_FIXEDMAP
|
|
* use a fixed address for the mmap region. This flag must be specified
|
|
* when creating the environment, and is stored persistently in the environment.
|
|
* If successful, the memory map will always reside at the same virtual address
|
|
* and pointers used to reference data items in the database will be constant
|
|
* across multiple invocations. This option may not always work, depending on
|
|
* 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
|
|
* 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.
|
|
* <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.
|
|
* <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,
|
|
* or next non-MDB_RDONLY commit or #mdb_env_sync(). This optimization
|
|
* maintains database integrity, but a system crash may undo the last
|
|
* committed transaction. I.e. it preserves the ACI (atomicity,
|
|
* consistency, isolation) but not D (durability) database property.
|
|
* This flag may be changed at any time using #mdb_env_set_flags().
|
|
* <li>#MDB_NOSYNC
|
|
* Don't flush system buffers to disk when committing a transaction.
|
|
* This optimization means a system crash can corrupt the database or
|
|
* lose the last transactions if buffers are not yet flushed to disk.
|
|
* The risk is governed by how often the system flushes dirty buffers
|
|
* to disk and how often #mdb_env_sync() is called. However, if the
|
|
* filesystem preserves write order and the #MDB_WRITEMAP flag is not
|
|
* used, transactions exhibit ACI (atomicity, consistency, isolation)
|
|
* properties and only lose D (durability). I.e. database integrity
|
|
* is maintained, but a system crash may undo the final transactions.
|
|
* Note that (#MDB_NOSYNC | #MDB_WRITEMAP) leaves the system with no
|
|
* hint for when to write transactions to disk, unless #mdb_env_sync()
|
|
* is called. (#MDB_MAPASYNC | #MDB_WRITEMAP) may be preferable.
|
|
* This flag may be changed at any time using #mdb_env_set_flags().
|
|
* <li>#MDB_MAPASYNC
|
|
* When using #MDB_WRITEMAP, use asynchronous flushes to disk.
|
|
* As with #MDB_NOSYNC, a system crash can then corrupt the
|
|
* database or lose the last transactions. Calling #mdb_env_sync()
|
|
* ensures on-disk database integrity until next commit.
|
|
* This flag may be changed at any time using #mdb_env_set_flags().
|
|
* <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
|
|
* 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
|
|
* application must also serialize the write transactions in an OS
|
|
* thread, since MDB's write locking is unaware of the user threads.
|
|
* </ul>
|
|
* @param[in] mode The UNIX permissions to set on created files. This parameter
|
|
* is ignored on Windows.
|
|
* @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
|
|
* 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.
|
|
* <li>EACCES - the user didn't have permission to access the environment files.
|
|
* <li>EAGAIN - the environment was locked by another process.
|
|
* </ul>
|
|
*/
|
|
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.
|
|
*
|
|
* 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.
|
|
* @return A non-zero error value on failure and 0 on success.
|
|
*/
|
|
int mdb_env_copy(MDB_env *env, const char *path);
|
|
|
|
/** @brief Copy an MDB 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.
|
|
* @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.
|
|
* @return A non-zero error value on failure and 0 on success.
|
|
*/
|
|
int mdb_env_copyfd(MDB_env *env, mdb_filehandle_t fd);
|
|
|
|
/** @brief Return statistics about the MDB environment.
|
|
*
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[out] stat The address of an #MDB_stat structure
|
|
* where the statistics will be copied
|
|
*/
|
|
int mdb_env_stat(MDB_env *env, MDB_stat *stat);
|
|
|
|
/** @brief Return information about the MDB environment.
|
|
*
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[out] stat The address of an #MDB_envinfo structure
|
|
* where the information will be copied
|
|
*/
|
|
int mdb_env_info(MDB_env *env, MDB_envinfo *stat);
|
|
|
|
/** @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
|
|
* the OS buffers upon commit as well, unless the environment was
|
|
* opened with #MDB_NOSYNC or in part #MDB_NOMETASYNC.
|
|
* @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
|
|
* will be omitted, and with #MDB_MAPASYNC they will be asynchronous.
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* <li>EIO - an error occurred during synchronization.
|
|
* </ul>
|
|
*/
|
|
int mdb_env_sync(MDB_env *env, int force);
|
|
|
|
/** @brief Close the environment and release the memory map.
|
|
*
|
|
* Only a single thread may call this function. All transactions, databases,
|
|
* and cursors must already be closed before calling this function. Attempts to
|
|
* use any such handles after calling this function will cause a SIGSEGV.
|
|
* The environment handle will be freed and must not be used again after this call.
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
*/
|
|
void mdb_env_close(MDB_env *env);
|
|
|
|
/** @brief Set environment flags.
|
|
*
|
|
* This may be used to set some flags in addition to those from
|
|
* #mdb_env_open(), or to unset these flags.
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[in] flags The flags to change, bitwise OR'ed together
|
|
* @param[in] onoff A non-zero value sets the flags, zero clears them.
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_env_set_flags(MDB_env *env, unsigned int flags, int onoff);
|
|
|
|
/** @brief Get environment flags.
|
|
*
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[out] flags The address of an integer to store the flags
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_env_get_flags(MDB_env *env, unsigned int *flags);
|
|
|
|
/** @brief Return the path that was used in #mdb_env_open().
|
|
*
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[out] path Address of a string pointer to contain the path. This
|
|
* is the actual string in the environment, not a copy. It should not be
|
|
* altered in any way.
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_env_get_path(MDB_env *env, const char **path);
|
|
|
|
/** @brief Set the size of the memory map to use for this environment.
|
|
*
|
|
* The size should be a multiple of the OS page size. The default is
|
|
* 10485760 bytes. The size of the memory map is also the maximum size
|
|
* of the database. The value should be chosen as large as possible,
|
|
* to accommodate future growth of the database.
|
|
* This function may only be called after #mdb_env_create() and before #mdb_env_open().
|
|
* The size may be changed by closing and reopening the environment.
|
|
* Any attempt to set a size smaller than the space already consumed
|
|
* by the environment will be silently changed to the current size of the used space.
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[in] size The size in bytes
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified, or the environment is already open.
|
|
* </ul>
|
|
*/
|
|
int mdb_env_set_mapsize(MDB_env *env, size_t size);
|
|
|
|
/** @brief Set the maximum number of threads/reader slots for the environment.
|
|
*
|
|
* This defines the number of slots in the lock table that is used to track readers in the
|
|
* the environment. The default is 126.
|
|
* Starting a read-only transaction normally ties a lock table slot to the
|
|
* current thread until the environment closes or the thread exits. If
|
|
* MDB_NOTLS is in use, #mdb_txn_begin() instead ties the slot to the
|
|
* MDB_txn object until it or the #MDB_env object is destroyed.
|
|
* This function may only be called after #mdb_env_create() and before #mdb_env_open().
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[in] readers The maximum number of reader lock table slots
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified, or the environment is already open.
|
|
* </ul>
|
|
*/
|
|
int mdb_env_set_maxreaders(MDB_env *env, unsigned int readers);
|
|
|
|
/** @brief Get the maximum number of threads/reader slots for the environment.
|
|
*
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[out] readers Address of an integer to store the number of readers
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_env_get_maxreaders(MDB_env *env, unsigned int *readers);
|
|
|
|
/** @brief Set the maximum number of named databases for the environment.
|
|
*
|
|
* This function is only needed if multiple databases will be used in the
|
|
* environment. Simpler applications that use the environment as a single
|
|
* unnamed database can ignore this option.
|
|
* This function may only be called after #mdb_env_create() and before #mdb_env_open().
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[in] dbs The maximum number of databases
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified, or the environment is already open.
|
|
* </ul>
|
|
*/
|
|
int mdb_env_set_maxdbs(MDB_env *env, MDB_dbi dbs);
|
|
|
|
/** @brief Get the maximum size of a key for the environment.
|
|
*
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @return The maximum size of a key. (#MDB_MAXKEYSIZE)
|
|
*/
|
|
int mdb_env_get_maxkeysize(MDB_env *env);
|
|
|
|
/** @brief Create a transaction for use with the environment.
|
|
*
|
|
* The transaction handle may be discarded using #mdb_txn_abort() or #mdb_txn_commit().
|
|
* @note A transaction and its cursors must only be used by a single
|
|
* thread, and a thread may only have a single transaction at a time.
|
|
* If #MDB_NOTLS is in use, this does not apply to read-only transactions.
|
|
* @note Cursors may not span transactions.
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[in] parent If this parameter is non-NULL, the new transaction
|
|
* will be a nested transaction, with the transaction indicated by \b parent
|
|
* as its parent. Transactions may be nested to any level. A parent
|
|
* transaction and its cursors may not issue any other operations than
|
|
* mdb_txn_commit and mdb_txn_abort while it has active child transactions.
|
|
* @param[in] flags Special options for this transaction. This parameter
|
|
* must be set to 0 or by bitwise OR'ing together one or more of the
|
|
* values described here.
|
|
* <ul>
|
|
* <li>#MDB_RDONLY
|
|
* This transaction will not perform any write operations.
|
|
* </ul>
|
|
* @param[out] txn Address where the new #MDB_txn handle will be stored
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>#MDB_PANIC - a fatal error occurred earlier and the environment
|
|
* must be shut down.
|
|
* <li>#MDB_MAP_RESIZED - another process wrote data beyond this MDB_env's
|
|
* mapsize and the environment must be shut down.
|
|
* <li>#MDB_READERS_FULL - a read-only transaction was requested and
|
|
* the reader lock table is full. See #mdb_env_set_maxreaders().
|
|
* <li>ENOMEM - out of memory.
|
|
* </ul>
|
|
*/
|
|
int mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **txn);
|
|
|
|
/** @brief Returns the transaction's #MDB_env
|
|
*
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
*/
|
|
MDB_env *mdb_txn_env(MDB_txn *txn);
|
|
|
|
/** @brief Commit all the operations of a transaction into the database.
|
|
*
|
|
* The transaction handle is freed. It and its cursors must not be used
|
|
* again after this call, except with #mdb_cursor_renew().
|
|
* @note Earlier documentation incorrectly said all cursors would be freed.
|
|
* Only write-transactions free cursors.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* <li>ENOSPC - no more disk space.
|
|
* <li>EIO - a low-level I/O error occurred while writing.
|
|
* <li>ENOMEM - out of memory.
|
|
* </ul>
|
|
*/
|
|
int mdb_txn_commit(MDB_txn *txn);
|
|
|
|
/** @brief Abandon all the operations of the transaction instead of saving them.
|
|
*
|
|
* The transaction handle is freed. It and its cursors must not be used
|
|
* again after this call, except with #mdb_cursor_renew().
|
|
* @note Earlier documentation incorrectly said all cursors would be freed.
|
|
* Only write-transactions free cursors.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
*/
|
|
void mdb_txn_abort(MDB_txn *txn);
|
|
|
|
/** @brief Reset a read-only transaction.
|
|
*
|
|
* Abort the transaction like #mdb_txn_abort(), but keep the transaction
|
|
* handle. #mdb_txn_renew() may reuse the handle. This saves allocation
|
|
* overhead if the process will start a new read-only transaction soon,
|
|
* and also locking overhead if #MDB_NOTLS is in use. The reader table
|
|
* lock is released, but the table slot stays tied to its thread or
|
|
* #MDB_txn. Use mdb_txn_abort() to discard a reset handle, and to free
|
|
* its lock table slot if MDB_NOTLS is in use.
|
|
* Cursors opened within the transaction must not be used
|
|
* again after this call, except with #mdb_cursor_renew().
|
|
* Reader locks generally don't interfere with writers, but they keep old
|
|
* versions of database pages allocated. Thus they prevent the old pages
|
|
* from being reused when writers commit new data, and so under heavy load
|
|
* the database size may grow much more rapidly than otherwise.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
*/
|
|
void mdb_txn_reset(MDB_txn *txn);
|
|
|
|
/** @brief Renew a read-only transaction.
|
|
*
|
|
* This acquires a new reader lock for a transaction handle that had been
|
|
* released by #mdb_txn_reset(). It must be called before a reset transaction
|
|
* may be used again.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>#MDB_PANIC - a fatal error occurred earlier and the environment
|
|
* must be shut down.
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_txn_renew(MDB_txn *txn);
|
|
|
|
/** Compat with version <= 0.9.4, avoid clash with libmdb from MDB Tools project */
|
|
#define mdb_open(txn,name,flags,dbi) mdb_dbi_open(txn,name,flags,dbi)
|
|
/** Compat with version <= 0.9.4, avoid clash with libmdb from MDB Tools project */
|
|
#define mdb_close(env,dbi) mdb_dbi_close(env,dbi)
|
|
|
|
/** @brief Open a database in the environment.
|
|
*
|
|
* A database handle denotes the name and parameters of a database,
|
|
* independently of whether such a database exists.
|
|
* The database handle may be discarded by calling #mdb_dbi_close().
|
|
* The old database handle is returned if the database was already open.
|
|
* The handle must only be closed once.
|
|
* The database handle will be private to the current transaction until
|
|
* the transaction is successfully committed. If the transaction is
|
|
* aborted the handle will be closed automatically.
|
|
* 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.
|
|
*
|
|
* To use named databases (with name != NULL), #mdb_env_set_maxdbs()
|
|
* must be called before opening the environment.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] name The name of the database to open. If only a single
|
|
* database is needed in the environment, this value may be NULL.
|
|
* @param[in] flags Special options for this database. This parameter
|
|
* must be set to 0 or by bitwise OR'ing together one or more of the
|
|
* values described here.
|
|
* <ul>
|
|
* <li>#MDB_REVERSEKEY
|
|
* Keys are strings to be compared in reverse order, from the end
|
|
* of the strings to the beginning. By default, Keys are treated as strings and
|
|
* compared from beginning to end.
|
|
* <li>#MDB_DUPSORT
|
|
* Duplicate keys may be used in the database. (Or, from another perspective,
|
|
* keys may have multiple data items, stored in sorted order.) By default
|
|
* keys must be unique and may have only a single data item.
|
|
* <li>#MDB_INTEGERKEY
|
|
* Keys are binary integers in native byte order. Setting this option
|
|
* requires all keys to be the same size, typically sizeof(int)
|
|
* or sizeof(size_t).
|
|
* <li>#MDB_DUPFIXED
|
|
* 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.
|
|
* <li>#MDB_INTEGERDUP
|
|
* This option specifies that duplicate data items are also integers, and
|
|
* should be sorted as such.
|
|
* <li>#MDB_REVERSEDUP
|
|
* This option specifies that duplicate data items should be compared as
|
|
* strings in reverse order.
|
|
* <li>#MDB_CREATE
|
|
* Create the named database if it doesn't exist. This option is not
|
|
* allowed in a read-only transaction or a read-only environment.
|
|
* </ul>
|
|
* @param[out] dbi Address where the new #MDB_dbi handle will be stored
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>#MDB_NOTFOUND - the specified database doesn't exist in the environment
|
|
* and #MDB_CREATE was not specified.
|
|
* <li>#MDB_DBS_FULL - too many databases have been opened. See #mdb_env_set_maxdbs().
|
|
* </ul>
|
|
*/
|
|
int mdb_dbi_open(MDB_txn *txn, const char *name, unsigned int flags, MDB_dbi *dbi);
|
|
|
|
/** @brief Retrieve statistics for a database.
|
|
*
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[out] stat The address of an #MDB_stat structure
|
|
* where the statistics will be copied
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_stat(MDB_txn *txn, MDB_dbi dbi, MDB_stat *stat);
|
|
|
|
/** @brief Retrieve the DB flags for a database handle.
|
|
*
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[out] flags Address where the flags will be returned.
|
|
* @return A non-zero error value on failure and 0 on success.
|
|
*/
|
|
int mdb_dbi_flags(MDB_env *env, MDB_dbi dbi, unsigned int *flags);
|
|
|
|
/** @brief Close a database handle.
|
|
*
|
|
* This call is not mutex protected. Handles should only be closed by
|
|
* a single thread, and only if no other threads are going to reference
|
|
* the database handle or one of its cursors any further. Do not close
|
|
* a handle if an existing transaction has modified its database.
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
*/
|
|
void mdb_dbi_close(MDB_env *env, MDB_dbi dbi);
|
|
|
|
/** @brief Empty or delete+close a database.
|
|
*
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[in] del 0 to empty the DB, 1 to delete it from the
|
|
* environment and close the DB handle.
|
|
* @return A non-zero error value on failure and 0 on success.
|
|
*/
|
|
int mdb_drop(MDB_txn *txn, MDB_dbi dbi, int del);
|
|
|
|
/** @brief Set a custom key comparison function for a database.
|
|
*
|
|
* The comparison function is called whenever it is necessary to compare a
|
|
* key specified by the application with a key currently stored in the database.
|
|
* If no comparison function is specified, and no special key flags were specified
|
|
* with #mdb_dbi_open(), the keys are compared lexically, with shorter keys collating
|
|
* before longer keys.
|
|
* @warning This function must be called before any data access functions are used,
|
|
* otherwise data corruption may occur. The same comparison function must be used by every
|
|
* program accessing the database, every time the database is used.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[in] cmp A #MDB_cmp_func function
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_set_compare(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp);
|
|
|
|
/** @brief Set a custom data comparison function for a #MDB_DUPSORT database.
|
|
*
|
|
* This comparison function is called whenever it is necessary to compare a data
|
|
* item specified by the application with a data item currently stored in the database.
|
|
* This function only takes effect if the database was opened with the #MDB_DUPSORT
|
|
* flag.
|
|
* If no comparison function is specified, and no special key flags were specified
|
|
* with #mdb_dbi_open(), the data items are compared lexically, with shorter items collating
|
|
* before longer items.
|
|
* @warning This function must be called before any data access functions are used,
|
|
* otherwise data corruption may occur. The same comparison function must be used by every
|
|
* program accessing the database, every time the database is used.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[in] cmp A #MDB_cmp_func function
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_set_dupsort(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp);
|
|
|
|
/** @brief Set a relocation function for a #MDB_FIXEDMAP database.
|
|
*
|
|
* @todo The relocation function is called whenever it is necessary to move the data
|
|
* of an item to a different position in the database (e.g. through tree
|
|
* balancing operations, shifts as a result of adds or deletes, etc.). It is
|
|
* intended to allow address/position-dependent data items to be stored in
|
|
* a database in an environment opened with the #MDB_FIXEDMAP option.
|
|
* Currently the relocation feature is unimplemented and setting
|
|
* this function has no effect.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[in] rel A #MDB_rel_func function
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_set_relfunc(MDB_txn *txn, MDB_dbi dbi, MDB_rel_func *rel);
|
|
|
|
/** @brief Set a context pointer for a #MDB_FIXEDMAP database's relocation function.
|
|
*
|
|
* See #mdb_set_relfunc and #MDB_rel_func for more details.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[in] ctx An arbitrary pointer for whatever the application needs.
|
|
* It will be passed to the callback function set by #mdb_set_relfunc
|
|
* as its \b relctx parameter whenever the callback is invoked.
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_set_relctx(MDB_txn *txn, MDB_dbi dbi, void *ctx);
|
|
|
|
/** @brief Get items from a database.
|
|
*
|
|
* This function retrieves key/data pairs from the database. The address
|
|
* and length of the data associated with the specified \b key are returned
|
|
* in the structure to which \b data refers.
|
|
* If the database supports duplicate keys (#MDB_DUPSORT) then the
|
|
* first data item for the key will be returned. Retrieval of other
|
|
* items requires the use of #mdb_cursor_get().
|
|
*
|
|
* @note The memory pointed to by the returned values is owned by the
|
|
* database. The caller need not dispose of the memory, and may not
|
|
* modify it in any way. For values returned in a read-only transaction
|
|
* any modification attempts will cause a SIGSEGV.
|
|
* @note Values returned from the database are valid only until a
|
|
* subsequent update operation, or the end of the transaction.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[in] key The key to search for in the database
|
|
* @param[out] data The data corresponding to the key
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>#MDB_NOTFOUND - the key was not in the database.
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_get(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data);
|
|
|
|
/** @brief Store items into a database.
|
|
*
|
|
* This function stores key/data pairs in the database. The default behavior
|
|
* is to enter the new key/data pair, replacing any previously existing key
|
|
* if duplicates are disallowed, or adding a duplicate data item if
|
|
* duplicates are allowed (#MDB_DUPSORT).
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[in] key The key to store in the database
|
|
* @param[in,out] data The data to store
|
|
* @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_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
|
|
* return #MDB_KEYEXIST if the key/data pair already appears in the
|
|
* database.
|
|
* <li>#MDB_NOOVERWRITE - enter the new key/data pair only if the key
|
|
* does not already appear in the database. The function will return
|
|
* #MDB_KEYEXIST if the key already appears in the database, even if
|
|
* the database supports duplicates (#MDB_DUPSORT). The \b data
|
|
* parameter will be set to point to the existing item.
|
|
* <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 - before
|
|
* the next update operation or the transaction ends. This saves
|
|
* an extra memcpy if the data is being generated later.
|
|
* <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.
|
|
* <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
|
|
* errors are:
|
|
* <ul>
|
|
* <li>#MDB_MAP_FULL - the database is full, see #mdb_env_set_mapsize().
|
|
* <li>#MDB_TXN_FULL - the transaction has too many dirty pages.
|
|
* <li>EACCES - an attempt was made to write in a read-only transaction.
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_put(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data,
|
|
unsigned int flags);
|
|
|
|
/** @brief Delete items from a database.
|
|
*
|
|
* This function removes key/data pairs from the database.
|
|
* If the database does not support sorted duplicate data items
|
|
* (#MDB_DUPSORT) the data parameter is ignored.
|
|
* If the database supports sorted duplicates and the data parameter
|
|
* is NULL, all of the duplicate data items for the key will be
|
|
* deleted. Otherwise, if the data parameter is non-NULL
|
|
* only the matching data item will be deleted.
|
|
* This function will return #MDB_NOTFOUND if the specified key/data
|
|
* pair is not in the database.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[in] key The key to delete from the database
|
|
* @param[in] data The data to delete
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EACCES - an attempt was made to write in a read-only transaction.
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_del(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data);
|
|
|
|
/** @brief Create a cursor handle.
|
|
*
|
|
* A cursor is associated with a specific transaction and database.
|
|
* A cursor cannot be used when its database handle is closed. Nor
|
|
* when its transaction has ended, except with #mdb_cursor_renew().
|
|
* It can be discarded with #mdb_cursor_close().
|
|
* A cursor in a write-transaction can be closed before its transaction
|
|
* ends, and will otherwise be closed when its transaction ends.
|
|
* A cursor in a read-only transaction must be closed explicitly, before
|
|
* or after its transaction ends. It can be reused with
|
|
* #mdb_cursor_renew() before finally closing it.
|
|
* @note Earlier documentation said that cursors in every transaction
|
|
* were closed when the transaction committed or aborted.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[out] cursor Address where the new #MDB_cursor handle will be stored
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_cursor_open(MDB_txn *txn, MDB_dbi dbi, MDB_cursor **cursor);
|
|
|
|
/** @brief Close a cursor handle.
|
|
*
|
|
* The cursor handle will be freed and must not be used again after this call.
|
|
* Its transaction must still be live if it is a write-transaction.
|
|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open()
|
|
*/
|
|
void mdb_cursor_close(MDB_cursor *cursor);
|
|
|
|
/** @brief Renew a cursor handle.
|
|
*
|
|
* A cursor is associated with a specific transaction and database.
|
|
* Cursors that are only used in read-only
|
|
* transactions may be re-used, to avoid unnecessary malloc/free overhead.
|
|
* The cursor may be associated with a new read-only transaction, and
|
|
* referencing the same database handle as it was created with.
|
|
* This may be done whether the previous transaction is live or dead.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open()
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_cursor_renew(MDB_txn *txn, MDB_cursor *cursor);
|
|
|
|
/** @brief Return the cursor's transaction handle.
|
|
*
|
|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open()
|
|
*/
|
|
MDB_txn *mdb_cursor_txn(MDB_cursor *cursor);
|
|
|
|
/** @brief Return the cursor's database handle.
|
|
*
|
|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open()
|
|
*/
|
|
MDB_dbi mdb_cursor_dbi(MDB_cursor *cursor);
|
|
|
|
/** @brief Retrieve by cursor.
|
|
*
|
|
* This function retrieves key/data pairs from the database. The address and length
|
|
* of the key are returned in the object to which \b key refers (except for the
|
|
* case of the #MDB_SET option, in which the \b key object is unchanged), and
|
|
* the address and length of the data are returned in the object to which \b data
|
|
* refers.
|
|
* See #mdb_get() for restrictions on using the output values.
|
|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open()
|
|
* @param[in,out] key The key for a retrieved item
|
|
* @param[in,out] data The data of a retrieved item
|
|
* @param[in] op A cursor operation #MDB_cursor_op
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>#MDB_NOTFOUND - no matching key found.
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_cursor_get(MDB_cursor *cursor, MDB_val *key, MDB_val *data,
|
|
MDB_cursor_op op);
|
|
|
|
/** @brief Store by cursor.
|
|
*
|
|
* This function stores key/data pairs into the database.
|
|
* If the function fails for any reason, the state of the cursor will be
|
|
* unchanged. If the function succeeds and an item is inserted into the
|
|
* database, the cursor is always positioned to refer to the newly inserted item.
|
|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open()
|
|
* @param[in] key The key operated on.
|
|
* @param[in] data The data operated on.
|
|
* @param[in] flags Options for this operation. This parameter
|
|
* must be set to 0 or one of the values described here.
|
|
* <ul>
|
|
* <li>#MDB_CURRENT - overwrite the data of the key/data pair to which
|
|
* the cursor refers with the specified data item. The \b key
|
|
* parameter is ignored.
|
|
* <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
|
|
* return #MDB_KEYEXIST if the key/data pair already appears in the
|
|
* database.
|
|
* <li>#MDB_NOOVERWRITE - enter the new key/data pair only if the key
|
|
* does not already appear in the database. The function will return
|
|
* #MDB_KEYEXIST if the key already appears in the database, even if
|
|
* 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
|
|
* an extra memcpy if the data is being generated later.
|
|
* <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.
|
|
* <li>#MDB_APPENDDUP - as above, but for sorted dup data.
|
|
* <li>#MDB_MULTIPLE - store multiple contiguous data elements in a
|
|
* single request. This flag may only be specified if the database
|
|
* was opened with #MDB_DUPFIXED. The \b data argument must be an
|
|
* array of two MDB_vals. The mv_size of the first MDB_val must be
|
|
* the size of a single data element. The mv_data of the first MDB_val
|
|
* must point to the beginning of the array of contiguous data elements.
|
|
* The mv_size of the second MDB_val must be the count of the number
|
|
* of data elements to store. On return this field will be set to
|
|
* the count of the number of elements actually written. The mv_data
|
|
* of the second MDB_val is unused.
|
|
* </ul>
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>#MDB_MAP_FULL - the database is full, see #mdb_env_set_mapsize().
|
|
* <li>#MDB_TXN_FULL - the transaction has too many dirty pages.
|
|
* <li>EACCES - an attempt was made to modify a read-only database.
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_cursor_put(MDB_cursor *cursor, MDB_val *key, MDB_val *data,
|
|
unsigned int flags);
|
|
|
|
/** @brief Delete current key/data pair
|
|
*
|
|
* This function deletes the key/data pair to which the cursor refers.
|
|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open()
|
|
* @param[in] flags Options for this operation. This parameter
|
|
* must be set to 0 or one of the values described here.
|
|
* <ul>
|
|
* <li>#MDB_NODUPDATA - delete all of the data items for the current key.
|
|
* This flag may only be specified if the database was opened with #MDB_DUPSORT.
|
|
* </ul>
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EACCES - an attempt was made to modify a read-only database.
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_cursor_del(MDB_cursor *cursor, unsigned int flags);
|
|
|
|
/** @brief Return count of duplicates for current key.
|
|
*
|
|
* This call is only valid on databases that support sorted duplicate
|
|
* data items #MDB_DUPSORT.
|
|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open()
|
|
* @param[out] countp Address where the count will be stored
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EINVAL - cursor is not initialized, or an invalid parameter was specified.
|
|
* </ul>
|
|
*/
|
|
int mdb_cursor_count(MDB_cursor *cursor, size_t *countp);
|
|
|
|
/** @brief Compare two data items according to a particular database.
|
|
*
|
|
* This returns a comparison as if the two data items were keys in the
|
|
* specified database.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[in] a The first item to compare
|
|
* @param[in] b The second item to compare
|
|
* @return < 0 if a < b, 0 if a == b, > 0 if a > b
|
|
*/
|
|
int mdb_cmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b);
|
|
|
|
/** @brief Compare two data items according to a particular database.
|
|
*
|
|
* This returns a comparison as if the two items were data items of
|
|
* the specified database. The database must have the #MDB_DUPSORT flag.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_dbi_open()
|
|
* @param[in] a The first item to compare
|
|
* @param[in] b The second item to compare
|
|
* @return < 0 if a < b, 0 if a == b, > 0 if a > b
|
|
*/
|
|
int mdb_dcmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b);
|
|
|
|
/** @brief A callback function used to print a message from the library.
|
|
*
|
|
* @param[in] msg The string to be printed.
|
|
* @param[in] ctx An arbitrary context pointer for the callback.
|
|
* @return < 0 on failure, 0 on success.
|
|
*/
|
|
typedef int (MDB_msg_func)(const char *msg, void *ctx);
|
|
|
|
/** @brief Dump the entries in the reader lock table.
|
|
*
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[in] func A #MDB_msg_func function
|
|
* @param[in] ctx Anything the message function needs
|
|
* @return < 0 on failure, 0 on success.
|
|
*/
|
|
int mdb_reader_list(MDB_env *env, MDB_msg_func *func, void *ctx);
|
|
|
|
/** @brief Check for stale entries in the reader lock table.
|
|
*
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[out] dead Number of stale slots that were cleared
|
|
* @return 0 on success, non-zero on failure.
|
|
*/
|
|
int mdb_reader_check(MDB_env *env, int *dead);
|
|
/** @} */
|
|
|
|
#ifdef __cplusplus
|
|
}
|
|
#endif
|
|
#endif /* _LMDB_H_ */
|