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1654 lines
74 KiB
1654 lines
74 KiB
/** @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 (LMDB)
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*
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* @section intro_sec Introduction
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* LMDB 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, LMDB 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. LMDB 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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* If this is your first time using a transactional embedded key/value
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* store, you may find the \ref starting page to be helpful.
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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: Check for stale readers periodically, using the
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* #mdb_reader_check function or the \ref mdb_stat_1 "mdb_stat" tool.
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* Stale writers will be cleared automatically on most systems:
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* - Windows - automatic
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* - BSD, systems using SysV semaphores - automatic
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* - Linux, systems using POSIX mutexes with Robust option - automatic
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* Otherwise just make all programs using the database close it;
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* the lockfile is always reset on first open of the environment.
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*
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* - On BSD systems or others configured with MDB_USE_SYSV_SEM or
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* 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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* - There is normally no pure read-only mode, since readers need write
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* access to locks and lock file. Exceptions: On read-only filesystems
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* or with the #MDB_NOLOCK flag described under #mdb_env_open().
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*
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* - An LMDB configuration will often reserve considerable \b unused
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* memory address space and maybe file size for future growth.
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* This does not use actual memory or disk space, but users may need
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* to understand the difference so they won't be scared off.
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*
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* - By default, in versions before 0.9.10, unused portions of the data
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* file might receive garbage data from memory freed by other code.
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* (This does not happen when using the #MDB_WRITEMAP flag.) As of
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* 0.9.10 the default behavior is to initialize such memory before
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* writing to the data file. Since there may be a slight performance
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* cost due to this initialization, applications may disable it using
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* the #MDB_NOMEMINIT flag. Applications handling sensitive data
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* which must not be written should not use this flag. This flag is
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* irrelevant when using #MDB_WRITEMAP.
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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, not after fork().
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*
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* - Do not have open an LMDB 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 fcntl() advisory locking. (It is OK to reopen it after
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* fork() - exec*(), since the lockfile has FD_CLOEXEC set.)
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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 a check
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* for stale readers is performed or the lockfile is reset,
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* since the process may not remove it from the lockfile.
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*
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* This does not apply to write transactions if the system clears
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* stale writers, see above.
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*
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* - If you do that anyway, do a periodic check for stale readers. Or
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* close the environment once in a while, so the lockfile can get reset.
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*
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* - Do not use LMDB 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 2011-2019 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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#include <inttypes.h>
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#include <limits.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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#ifdef _WIN32
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# define MDB_FMT_Z "I"
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#else
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# define MDB_FMT_Z "z" /**< printf/scanf format modifier for size_t */
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#endif
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#ifndef MDB_VL32
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/** Unsigned type used for mapsize, entry counts and page/transaction IDs.
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*
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* It is normally size_t, hence the name. Defining MDB_VL32 makes it
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* uint64_t, but do not try this unless you know what you are doing.
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*/
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typedef size_t mdb_size_t;
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# define MDB_SIZE_MAX SIZE_MAX /**< max #mdb_size_t */
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/** #mdb_size_t printf formats, \b t = one of [diouxX] without quotes */
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# define MDB_PRIy(t) MDB_FMT_Z #t
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/** #mdb_size_t scanf formats, \b t = one of [dioux] without quotes */
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# define MDB_SCNy(t) MDB_FMT_Z #t
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#else
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typedef uint64_t mdb_size_t;
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# define MDB_SIZE_MAX UINT64_MAX
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# define MDB_PRIy(t) PRI##t##64
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# define MDB_SCNy(t) SCN##t##64
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# define mdb_env_create mdb_env_create_vl32 /**< Prevent mixing with non-VL32 builds */
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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 LMDB 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 70
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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 "December 19, 2015"
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/** A stringifier for the version info */
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#define MDB_VERSTR(a,b,c,d) "LMDB " #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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* Values returned from the database are valid only until a subsequent
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* update operation, or the end of the transaction. Do not modify or
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* free them, they commonly point into the database itself.
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*
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* Key sizes must be between 1 and #mdb_env_get_maxkeysize() inclusive.
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* The 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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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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*/
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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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/** don't do any locking, caller must manage their own locks */
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#define MDB_NOLOCK 0x400000
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/** don't do readahead (no effect on Windows) */
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#define MDB_NORDAHEAD 0x800000
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/** don't initialize malloc'd memory before writing to datafile */
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#define MDB_NOMEMINIT 0x1000000
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/** use the previous snapshot rather than the latest one */
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#define MDB_PREVSNAPSHOT 0x2000000
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/** @} */
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/** @defgroup mdb_dbi_open Database 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, either unsigned int or #mdb_size_t.
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* (lmdb expects 32-bit int <= size_t <= 32/64-bit mdb_size_t.)
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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 #MDB_INTEGERKEY-style integers */
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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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/** @defgroup mdb_copy Copy Flags
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* @{
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*/
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/** Compacting copy: Omit free space from copy, and renumber all
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* pages sequentially.
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*/
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#define MDB_CP_COMPACT 0x01
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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 up to a page of duplicate data items
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from current cursor position. Move cursor to prepare
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for #MDB_NEXT_MULTIPLE. 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 up to a page of duplicate data items
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from next cursor position. Move cursor to prepare
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for #MDB_NEXT_MULTIPLE. 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_PREV_MULTIPLE /**< Position at previous page and return up to
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a page of duplicate data items. Only for #MDB_DUPFIXED */
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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 */
|
|
#define MDB_PAGE_NOTFOUND (-30797)
|
|
/** Located page was wrong type */
|
|
#define MDB_CORRUPTED (-30796)
|
|
/** Update of meta page failed or environment had fatal error */
|
|
#define MDB_PANIC (-30795)
|
|
/** Environment version mismatch */
|
|
#define MDB_VERSION_MISMATCH (-30794)
|
|
/** File is not a valid LMDB file */
|
|
#define MDB_INVALID (-30793)
|
|
/** Environment mapsize reached */
|
|
#define MDB_MAP_FULL (-30792)
|
|
/** Environment maxdbs reached */
|
|
#define MDB_DBS_FULL (-30791)
|
|
/** Environment maxreaders reached */
|
|
#define MDB_READERS_FULL (-30790)
|
|
/** Too many TLS keys in use - Windows only */
|
|
#define MDB_TLS_FULL (-30789)
|
|
/** Txn has too many dirty pages */
|
|
#define MDB_TXN_FULL (-30788)
|
|
/** Cursor stack too deep - internal error */
|
|
#define MDB_CURSOR_FULL (-30787)
|
|
/** Page has not enough space - internal error */
|
|
#define MDB_PAGE_FULL (-30786)
|
|
/** Database contents grew beyond environment mapsize */
|
|
#define MDB_MAP_RESIZED (-30785)
|
|
/** Operation and DB incompatible, or DB type changed. This can mean:
|
|
* <ul>
|
|
* <li>The operation expects an #MDB_DUPSORT / #MDB_DUPFIXED database.
|
|
* <li>Opening a named DB when the unnamed DB has #MDB_DUPSORT / #MDB_INTEGERKEY.
|
|
* <li>Accessing a data record as a database, or vice versa.
|
|
* <li>The database was dropped and recreated with different flags.
|
|
* </ul>
|
|
*/
|
|
#define MDB_INCOMPATIBLE (-30784)
|
|
/** Invalid reuse of reader locktable slot */
|
|
#define MDB_BAD_RSLOT (-30783)
|
|
/** Transaction must abort, has a child, or is invalid */
|
|
#define MDB_BAD_TXN (-30782)
|
|
/** Unsupported size of key/DB name/data, or wrong DUPFIXED size */
|
|
#define MDB_BAD_VALSIZE (-30781)
|
|
/** The specified DBI was changed unexpectedly */
|
|
#define MDB_BAD_DBI (-30780)
|
|
/** Unexpected problem - txn should abort */
|
|
#define MDB_PROBLEM (-30779)
|
|
/** The last defined error code */
|
|
#define MDB_LAST_ERRCODE MDB_PROBLEM
|
|
/** @} */
|
|
|
|
/** @brief Statistics for a database in the environment */
|
|
typedef struct MDB_stat {
|
|
unsigned int ms_psize; /**< Size of a database page.
|
|
This is currently the same for all databases. */
|
|
unsigned int ms_depth; /**< Depth (height) of the B-tree */
|
|
mdb_size_t ms_branch_pages; /**< Number of internal (non-leaf) pages */
|
|
mdb_size_t ms_leaf_pages; /**< Number of leaf pages */
|
|
mdb_size_t ms_overflow_pages; /**< Number of overflow pages */
|
|
mdb_size_t ms_entries; /**< Number of data items */
|
|
} MDB_stat;
|
|
|
|
/** @brief Information about the environment */
|
|
typedef struct MDB_envinfo {
|
|
void *me_mapaddr; /**< Address of map, if fixed */
|
|
mdb_size_t me_mapsize; /**< Size of the data memory map */
|
|
mdb_size_t me_last_pgno; /**< ID of the last used page */
|
|
mdb_size_t me_last_txnid; /**< ID of the last committed transaction */
|
|
unsigned int me_maxreaders; /**< max reader slots in the environment */
|
|
unsigned int me_numreaders; /**< max reader slots used in the environment */
|
|
} MDB_envinfo;
|
|
|
|
/** @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
|
|
* @param[out] patch if non-NULL, the library patch version number is copied here
|
|
* @retval "version string" The library version as a string
|
|
*/
|
|
char *mdb_version(int *major, int *minor, int *patch);
|
|
|
|
/** @brief Return a string describing a given error code.
|
|
*
|
|
* 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 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 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().
|
|
* 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, 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. 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 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_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 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
|
|
* the caller must enforce single-writer semantics, and must ensure
|
|
* that no readers are using old transactions while a writer is
|
|
* active. The simplest approach is to use an exclusive lock so that
|
|
* no readers may be active at all when a writer begins.
|
|
* <li>#MDB_NORDAHEAD
|
|
* Turn off readahead. Most operating systems perform readahead on
|
|
* read requests by default. This option turns it off if the OS
|
|
* supports it. Turning it off may help random read performance
|
|
* when the DB is larger than RAM and system RAM is full.
|
|
* The option is not implemented on Windows.
|
|
* <li>#MDB_NOMEMINIT
|
|
* Don't initialize malloc'd memory before writing to unused spaces
|
|
* in the data file. By default, memory for pages written to the data
|
|
* file is obtained using malloc. While these pages may be reused in
|
|
* subsequent transactions, freshly malloc'd pages will be initialized
|
|
* to zeroes before use. This avoids persisting leftover data from other
|
|
* code (that used the heap and subsequently freed the memory) into the
|
|
* data file. Note that many other system libraries may allocate
|
|
* and free memory from the heap for arbitrary uses. E.g., stdio may
|
|
* use the heap for file I/O buffers. This initialization step has a
|
|
* modest performance cost so some applications may want to disable
|
|
* it using this flag. This option can be a problem for applications
|
|
* which handle sensitive data like passwords, and it makes memory
|
|
* checkers like Valgrind noisy. This flag is not needed with #MDB_WRITEMAP,
|
|
* which writes directly to the mmap instead of using malloc for pages. The
|
|
* initialization is also skipped if #MDB_RESERVE is used; the
|
|
* caller is expected to overwrite all of the memory that was
|
|
* reserved in that case.
|
|
* This flag may be changed at any time using #mdb_env_set_flags().
|
|
* <li>#MDB_PREVSNAPSHOT
|
|
* Open the environment with the previous snapshot rather than the latest
|
|
* one. This loses the latest transaction, but may help work around some
|
|
* types of corruption. If opened with write access, this must be the
|
|
* only process using the environment. This flag is automatically reset
|
|
* after a write transaction is successfully committed.
|
|
* </ul>
|
|
* @param[in] mode The UNIX permissions to set on created files and semaphores.
|
|
* 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 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.
|
|
* <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 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.
|
|
* @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 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.
|
|
* @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 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.
|
|
* 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_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
|
|
* where the statistics will be copied
|
|
*/
|
|
int mdb_env_stat(MDB_env *env, MDB_stat *stat);
|
|
|
|
/** @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
|
|
* 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. LMDB always flushes
|
|
* the OS buffers upon commit as well, unless the environment was
|
|
* 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
|
|
* 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>EACCES - the environment is read-only.
|
|
* <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. If several threads
|
|
* change the flags at the same time, the result is undefined.
|
|
* @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 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.
|
|
* @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_fd(MDB_env *env, mdb_filehandle_t *fd);
|
|
|
|
/** @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 should be called after #mdb_env_create() and before #mdb_env_open().
|
|
* It may be called at later times if no transactions are active in
|
|
* this process. Note that the library does not check for this condition,
|
|
* the caller must ensure it explicitly.
|
|
*
|
|
* 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.
|
|
*
|
|
* 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 has
|
|
* an active write transaction.
|
|
* </ul>
|
|
*/
|
|
int mdb_env_set_mapsize(MDB_env *env, mdb_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().
|
|
*
|
|
* Currently a moderate number of slots are cheap but a huge number gets
|
|
* expensive: 7-120 words per transaction, and every #mdb_dbi_open()
|
|
* does a linear search of the opened slots.
|
|
* @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 keys and #MDB_DUPSORT data we can write.
|
|
*
|
|
* Depends on the compile-time constant #MDB_MAXKEYSIZE. Default 511.
|
|
* See @ref MDB_val.
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @return The maximum size of a key we can write
|
|
*/
|
|
int mdb_env_get_maxkeysize(MDB_env *env);
|
|
|
|
/** @brief Set application information associated with the #MDB_env.
|
|
*
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @param[in] ctx An arbitrary pointer for whatever the application needs.
|
|
* @return A non-zero error value on failure and 0 on success.
|
|
*/
|
|
int mdb_env_set_userctx(MDB_env *env, void *ctx);
|
|
|
|
/** @brief Get the application information associated with the #MDB_env.
|
|
*
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @return The pointer set by #mdb_env_set_userctx().
|
|
*/
|
|
void *mdb_env_get_userctx(MDB_env *env);
|
|
|
|
/** @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().
|
|
* @param[in] msg The assertion message, not including newline.
|
|
*/
|
|
typedef void MDB_assert_func(MDB_env *env, const char *msg);
|
|
|
|
/** Set or reset the assert() callback of the environment.
|
|
* Disabled if liblmdb is buillt with NDEBUG.
|
|
* @note This hack should become obsolete as lmdb's error handling matures.
|
|
* @param[in] env An environment handle returned by #mdb_env_create().
|
|
* @param[in] func An #MDB_assert_func function, or 0.
|
|
* @return A non-zero error value on failure and 0 on success.
|
|
*/
|
|
int mdb_env_set_assert(MDB_env *env, MDB_assert_func *func);
|
|
|
|
/** @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.
|
|
* <li>#MDB_NOSYNC
|
|
* Don't flush system buffers to disk when committing this transaction.
|
|
* <li>#MDB_NOMETASYNC
|
|
* Flush system buffers but omit metadata flush when committing this transaction.
|
|
* </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 this environment's map must be resized as well.
|
|
* See #mdb_env_set_mapsize().
|
|
* <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 Return the transaction's ID.
|
|
*
|
|
* This returns the identifier associated with this transaction. For a
|
|
* read-only transaction, this corresponds to the snapshot being read;
|
|
* concurrent readers will frequently have the same transaction ID.
|
|
*
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @return A transaction ID, valid if input is an active transaction.
|
|
*/
|
|
mdb_size_t mdb_txn_id(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 may 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 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 are
|
|
* keys in the unnamed database, and may be read but not written.
|
|
*
|
|
* @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, either unsigned int
|
|
* or #mdb_size_t, and will be sorted as such.
|
|
* (lmdb expects 32-bit int <= size_t <= 32/64-bit mdb_size_t.)
|
|
* The keys must all be of the same size.
|
|
* <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, #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.
|
|
* <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] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @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_txn *txn, MDB_dbi dbi, unsigned int *flags);
|
|
|
|
/** @brief Close a database handle. Normally unnecessary. Use with care:
|
|
*
|
|
* 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.
|
|
* Doing so can cause misbehavior from database corruption to errors
|
|
* like MDB_BAD_VALSIZE (since the DB name is gone).
|
|
*
|
|
* Closing a database handle is not necessary, but lets #mdb_dbi_open()
|
|
* reuse the handle value. Usually it's better to set a bigger
|
|
* #mdb_env_set_maxdbs(), unless that value would be large.
|
|
*
|
|
* @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.
|
|
*
|
|
* See #mdb_dbi_close() for restrictions about closing the DB handle.
|
|
* @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.
|
|
* LMDB does nothing else with this memory, the caller is expected
|
|
* to modify all of the space requested. 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
|
|
* 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
|
|
* 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.
|
|
* The cursor is positioned at the new item, or on failure usually near it.
|
|
* @note Earlier documentation incorrectly said errors would leave the
|
|
* state of the cursor unchanged.
|
|
* @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 - replace the item at the current cursor position.
|
|
* The \b key parameter must still be provided, and must match it.
|
|
* 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
|
|
* 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 - 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
|
|
* 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
|
|
* a #MDB_KEYEXIST error.
|
|
* <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 write in a read-only transaction.
|
|
* <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.
|
|
* This does not invalidate the cursor, so operations such as MDB_NEXT
|
|
* can still be used on it.
|
|
* Both MDB_NEXT and MDB_GET_CURRENT will return the same record after
|
|
* this operation.
|
|
* @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 write in a read-only transaction.
|
|
* <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, mdb_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
|
|
/** @page tools LMDB Command Line Tools
|
|
The following describes the command line tools that are available for LMDB.
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\li \ref mdb_copy_1
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\li \ref mdb_dump_1
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\li \ref mdb_load_1
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\li \ref mdb_stat_1
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*/
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#endif /* _LMDB_H_ */
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