mdb.c 264 KB
Newer Older
1
/** @file mdb.c
Howard Chu's avatar
Howard Chu committed
2
 *	@brief Lightning memory-mapped database library
3
4
5
6
 *
 *	A Btree-based database management library modeled loosely on the
 *	BerkeleyDB API, but much simplified.
 */
Howard Chu's avatar
Howard Chu committed
7
/*
Quanah Gibson-Mount's avatar
Quanah Gibson-Mount committed
8
 * Copyright 2011-2015 Howard Chu, Symas Corp.
Howard Chu's avatar
Howard Chu committed
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted only as authorized by the OpenLDAP
 * Public License.
 *
 * A copy of this license is available in the file LICENSE in the
 * top-level directory of the distribution or, alternatively, at
 * <http://www.OpenLDAP.org/license.html>.
 *
 * This code is derived from btree.c written by Martin Hedenfalk.
 *
 * Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
35
#ifndef _GNU_SOURCE
Hallvard Furuseth's avatar
Hallvard Furuseth committed
36
#define _GNU_SOURCE 1
37
#endif
Howard Chu's avatar
Howard Chu committed
38
#ifdef _WIN32
Howard Chu's avatar
Howard Chu committed
39
#include <malloc.h>
Howard Chu's avatar
Howard Chu committed
40
#include <windows.h>
Howard Chu's avatar
Howard Chu committed
41
42
43
44
45
/** getpid() returns int; MinGW defines pid_t but MinGW64 typedefs it
 *  as int64 which is wrong. MSVC doesn't define it at all, so just
 *  don't use it.
 */
#define MDB_PID_T	int
Howard Chu's avatar
Howard Chu committed
46
47
48
#define MDB_THR_T	DWORD
#include <sys/types.h>
#include <sys/stat.h>
Howard Chu's avatar
Howard Chu committed
49
50
#ifdef __GNUC__
# include <sys/param.h>
Howard Chu's avatar
Howard Chu committed
51
#else
Howard Chu's avatar
Howard Chu committed
52
53
54
55
56
57
58
59
# define LITTLE_ENDIAN	1234
# define BIG_ENDIAN	4321
# define BYTE_ORDER	LITTLE_ENDIAN
# ifndef SSIZE_MAX
#  define SSIZE_MAX	INT_MAX
# endif
#endif
#else
Howard Chu's avatar
Howard Chu committed
60
61
#include <sys/types.h>
#include <sys/stat.h>
Howard Chu's avatar
Howard Chu committed
62
#define MDB_PID_T	pid_t
Howard Chu's avatar
Howard Chu committed
63
#define MDB_THR_T	pthread_t
Howard Chu's avatar
Howard Chu committed
64
#include <sys/param.h>
Howard Chu's avatar
Howard Chu committed
65
66
67
68
69
#include <sys/uio.h>
#include <sys/mman.h>
#ifdef HAVE_SYS_FILE_H
#include <sys/file.h>
#endif
Howard Chu's avatar
Howard Chu committed
70
#include <fcntl.h>
Howard Chu's avatar
Howard Chu committed
71
#endif
Howard Chu's avatar
Howard Chu committed
72

Howard Chu's avatar
Howard Chu committed
73
74
75
76
77
78
79
80
81
#if defined(__mips) && defined(__linux)
/* MIPS has cache coherency issues, requires explicit cache control */
#include <asm/cachectl.h>
extern int cacheflush(char *addr, int nbytes, int cache);
#define CACHEFLUSH(addr, bytes, cache)	cacheflush(addr, bytes, cache)
#else
#define CACHEFLUSH(addr, bytes, cache)
#endif

82
83
#if defined(__linux) && !defined(MDB_FDATASYNC_WORKS)
/** fdatasync is broken on ext3/ext4fs on older kernels, see
Howard Chu's avatar
Howard Chu committed
84
85
86
 *	description in #mdb_env_open2 comments. You can safely
 *	define MDB_FDATASYNC_WORKS if this code will only be run
 *	on kernels 3.6 and newer.
87
88
89
 */
#define	BROKEN_FDATASYNC
#endif
90

Howard Chu's avatar
Howard Chu committed
91
#include <errno.h>
92
#include <limits.h>
Howard Chu's avatar
Howard Chu committed
93
#include <stddef.h>
94
#include <inttypes.h>
Howard Chu's avatar
Howard Chu committed
95
96
97
98
99
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
100

Howard Chu's avatar
Howard Chu committed
101
#if defined(__sun) || defined(ANDROID)
102
103
104
105
106
/* Most platforms have posix_memalign, older may only have memalign */
#define HAVE_MEMALIGN	1
#include <malloc.h>
#endif

107
#if !(defined(BYTE_ORDER) || defined(__BYTE_ORDER))
108
#include <netinet/in.h>
109
110
111
#include <resolv.h>	/* defines BYTE_ORDER on HPUX and Solaris */
#endif

112
#if defined(__APPLE__) || defined (BSD)
113
# define MDB_USE_SYSV_SEM	1
114
115
116
# define MDB_FDATASYNC		fsync
#elif defined(ANDROID)
# define MDB_FDATASYNC		fsync
117
118
#endif

119
120
#ifndef _WIN32
#include <pthread.h>
121
122
123
124
125
126
127
128
129
130
131
132
#ifdef MDB_USE_SYSV_SEM
#include <sys/ipc.h>
#include <sys/sem.h>
#ifdef _SEM_SEMUN_UNDEFINED
union semun {
	int val;
	struct semid_ds *buf;
	unsigned short *array;
};
#endif /* _SEM_SEMUN_UNDEFINED */
#endif /* MDB_USE_SYSV_SEM */
#endif /* !_WIN32 */
Howard Chu's avatar
Howard Chu committed
133

134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
#ifdef USE_VALGRIND
#include <valgrind/memcheck.h>
#define VGMEMP_CREATE(h,r,z)    VALGRIND_CREATE_MEMPOOL(h,r,z)
#define VGMEMP_ALLOC(h,a,s) VALGRIND_MEMPOOL_ALLOC(h,a,s)
#define VGMEMP_FREE(h,a) VALGRIND_MEMPOOL_FREE(h,a)
#define VGMEMP_DESTROY(h)	VALGRIND_DESTROY_MEMPOOL(h)
#define VGMEMP_DEFINED(a,s)	VALGRIND_MAKE_MEM_DEFINED(a,s)
#else
#define VGMEMP_CREATE(h,r,z)
#define VGMEMP_ALLOC(h,a,s)
#define VGMEMP_FREE(h,a)
#define VGMEMP_DESTROY(h)
#define VGMEMP_DEFINED(a,s)
#endif

Howard Chu's avatar
Howard Chu committed
149
#ifndef BYTE_ORDER
Howard Chu's avatar
Howard Chu committed
150
151
152
153
154
155
156
157
158
159
160
161
# if (defined(_LITTLE_ENDIAN) || defined(_BIG_ENDIAN)) && !(defined(_LITTLE_ENDIAN) && defined(_BIG_ENDIAN))
/* Solaris just defines one or the other */
#  define LITTLE_ENDIAN	1234
#  define BIG_ENDIAN	4321
#  ifdef _LITTLE_ENDIAN
#   define BYTE_ORDER  LITTLE_ENDIAN
#  else
#   define BYTE_ORDER  BIG_ENDIAN
#  endif
# else
#  define BYTE_ORDER   __BYTE_ORDER
# endif
Howard Chu's avatar
Howard Chu committed
162
#endif
Howard Chu's avatar
Howard Chu committed
163

Howard Chu's avatar
Howard Chu committed
164
165
166
167
168
#ifndef LITTLE_ENDIAN
#define LITTLE_ENDIAN	__LITTLE_ENDIAN
#endif
#ifndef BIG_ENDIAN
#define BIG_ENDIAN	__BIG_ENDIAN
169
170
#endif

Howard Chu's avatar
Howard Chu committed
171
#if defined(__i386) || defined(__x86_64) || defined(_M_IX86)
Howard Chu's avatar
Howard Chu committed
172
173
174
#define MISALIGNED_OK	1
#endif

Howard Chu's avatar
Howard Chu committed
175
#include "lmdb.h"
176
177
#include "midl.h"

Howard Chu's avatar
Howard Chu committed
178
179
#if (BYTE_ORDER == LITTLE_ENDIAN) == (BYTE_ORDER == BIG_ENDIAN)
# error "Unknown or unsupported endianness (BYTE_ORDER)"
180
181
182
183
#elif (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
# error "Two's complement, reasonably sized integer types, please"
#endif

184
185
#ifdef __GNUC__
/** Put infrequently used env functions in separate section */
Howard Chu's avatar
Howard Chu committed
186
187
188
189
190
# ifdef __APPLE__
#  define	ESECT	__attribute__ ((section("__TEXT,text_env")))
# else
#  define	ESECT	__attribute__ ((section("text_env")))
# endif
191
192
193
194
#else
#define ESECT
#endif

Howard Chu's avatar
Howard Chu committed
195
/** @defgroup internal	LMDB Internals
196
197
 *	@{
 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
198
/** @defgroup compat	Compatibility Macros
Howard Chu's avatar
Howard Chu committed
199
200
201
202
 *	A bunch of macros to minimize the amount of platform-specific ifdefs
 *	needed throughout the rest of the code. When the features this library
 *	needs are similar enough to POSIX to be hidden in a one-or-two line
 *	replacement, this macro approach is used.
203
204
 *	@{
 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
205

Hallvard Furuseth's avatar
Hallvard Furuseth committed
206
	/** Features under development */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
207
208
#ifndef MDB_DEVEL
#define MDB_DEVEL 0
Hallvard Furuseth's avatar
Hallvard Furuseth committed
209
210
#endif

211
#if defined(_WIN32) || defined(MDB_USE_SYSV_SEM) || defined(EOWNERDEAD)
Hallvard Furuseth's avatar
Hallvard Furuseth committed
212
#define MDB_ROBUST_SUPPORTED	1
Hallvard Furuseth's avatar
Hallvard Furuseth committed
213
214
#endif

Hallvard Furuseth's avatar
Hallvard Furuseth committed
215
216
217
218
219
220
221
222
223
224
	/** Wrapper around __func__, which is a C99 feature */
#if __STDC_VERSION__ >= 199901L
# define mdb_func_	__func__
#elif __GNUC__ >= 2 || _MSC_VER >= 1300
# define mdb_func_	__FUNCTION__
#else
/* If a debug message says <mdb_unknown>(), update the #if statements above */
# define mdb_func_	"<mdb_unknown>"
#endif

225
226
227
228
229
230
231
232
233
234
/* Internal error codes, not exposed outside liblmdb */
#define	MDB_NO_ROOT		(MDB_LAST_ERRCODE + 10)
#ifdef _WIN32
#define MDB_OWNERDEAD	((int) WAIT_ABANDONED)
#elif defined MDB_USE_SYSV_SEM
#define MDB_OWNERDEAD	(MDB_LAST_ERRCODE + 11)
#else
#define MDB_OWNERDEAD	EOWNERDEAD
#endif

Howard Chu's avatar
Howard Chu committed
235
#ifdef _WIN32
Howard Chu's avatar
Howard Chu committed
236
#define MDB_USE_HASH	1
237
#define MDB_PIDLOCK	0
Howard Chu's avatar
Howard Chu committed
238
239
#define THREAD_RET	DWORD
#define pthread_t	HANDLE
Howard Chu's avatar
Howard Chu committed
240
#define pthread_mutex_t	HANDLE
Howard Chu's avatar
Howard Chu committed
241
#define pthread_cond_t	HANDLE
Hallvard Furuseth's avatar
Hallvard Furuseth committed
242
typedef HANDLE mdb_mutex_t;
Howard Chu's avatar
Howard Chu committed
243
244
#define pthread_key_t	DWORD
#define pthread_self()	GetCurrentThreadId()
245
246
#define pthread_key_create(x,y)	\
	((*(x) = TlsAlloc()) == TLS_OUT_OF_INDEXES ? ErrCode() : 0)
Howard Chu's avatar
Howard Chu committed
247
248
#define pthread_key_delete(x)	TlsFree(x)
#define pthread_getspecific(x)	TlsGetValue(x)
249
#define pthread_setspecific(x,y)	(TlsSetValue(x,y) ? 0 : ErrCode())
Howard Chu's avatar
Howard Chu committed
250
251
#define pthread_mutex_unlock(x)	ReleaseMutex(*x)
#define pthread_mutex_lock(x)	WaitForSingleObject(*x, INFINITE)
Howard Chu's avatar
Howard Chu committed
252
#define pthread_cond_signal(x)	SetEvent(*x)
Howard Chu's avatar
Howard Chu committed
253
#define pthread_cond_wait(cond,mutex)	do{SignalObjectAndWait(*mutex, *cond, INFINITE, FALSE); WaitForSingleObject(*mutex, INFINITE);}while(0)
Howard Chu's avatar
Howard Chu committed
254
255
#define THREAD_CREATE(thr,start,arg)	thr=CreateThread(NULL,0,start,arg,0,NULL)
#define THREAD_FINISH(thr)	WaitForSingleObject(thr, INFINITE)
Hallvard Furuseth's avatar
Hallvard Furuseth committed
256
257
258
#define MDB_MUTEX(env, rw)		((env)->me_##rw##mutex)
#define LOCK_MUTEX0(mutex)		WaitForSingleObject(mutex, INFINITE)
#define UNLOCK_MUTEX(mutex)		ReleaseMutex(mutex)
259
#define mdb_mutex_consistent(mutex)	0
Howard Chu's avatar
Howard Chu committed
260
#define getpid()	GetCurrentProcessId()
261
#define	MDB_FDATASYNC(fd)	(!FlushFileBuffers(fd))
262
#define	MDB_MSYNC(addr,len,flags)	(!FlushViewOfFile(addr,len))
Howard Chu's avatar
Howard Chu committed
263
#define	ErrCode()	GetLastError()
Hallvard Furuseth's avatar
Hallvard Furuseth committed
264
#define GET_PAGESIZE(x) {SYSTEM_INFO si; GetSystemInfo(&si); (x) = si.dwPageSize;}
265
#define	close(fd)	(CloseHandle(fd) ? 0 : -1)
Howard Chu's avatar
Howard Chu committed
266
#define	munmap(ptr,len)	UnmapViewOfFile(ptr)
Hallvard Furuseth's avatar
Hallvard Furuseth committed
267
#ifdef PROCESS_QUERY_LIMITED_INFORMATION
Hallvard Furuseth's avatar
Hallvard Furuseth committed
268
269
270
271
#define MDB_PROCESS_QUERY_LIMITED_INFORMATION PROCESS_QUERY_LIMITED_INFORMATION
#else
#define MDB_PROCESS_QUERY_LIMITED_INFORMATION 0x1000
#endif
272
#define	Z	"I"
Howard Chu's avatar
Howard Chu committed
273
#else
Howard Chu's avatar
Howard Chu committed
274
275
276
#define THREAD_RET	void *
#define THREAD_CREATE(thr,start,arg)	pthread_create(&thr,NULL,start,arg)
#define THREAD_FINISH(thr)	pthread_join(thr,NULL)
277
#define	Z	"z"			/**< printf format modifier for size_t */
278

279
280
281
	/** For MDB_LOCK_FORMAT: True if readers take a pid lock in the lockfile */
#define MDB_PIDLOCK			1

282
#ifdef MDB_USE_SYSV_SEM
283

284
285
286
typedef struct mdb_mutex {
	int semid;
	int semnum;
287
	int *locked;
288
289
290
} mdb_mutex_t;

#define MDB_MUTEX(env, rw)		(&(env)->me_##rw##mutex)
Hallvard Furuseth's avatar
Hallvard Furuseth committed
291
#define LOCK_MUTEX0(mutex)		mdb_sem_wait(mutex)
292
293
294
#define UNLOCK_MUTEX(mutex)		do { \
	struct sembuf sb = { 0, 1, SEM_UNDO }; \
	sb.sem_num = (mutex)->semnum; \
295
	*(mutex)->locked = 0; \
296
297
	semop((mutex)->semid, &sb, 1); \
} while(0)
298
299

static int
300
mdb_sem_wait(mdb_mutex_t *sem)
301
{
302
303
304
305
306
307
308
309
310
311
312
	int rc, *locked = sem->locked;
	struct sembuf sb = { 0, -1, SEM_UNDO };
	sb.sem_num = sem->semnum;
	do {
		if (!semop(sem->semid, &sb, 1)) {
			rc = *locked ? MDB_OWNERDEAD : MDB_SUCCESS;
			*locked = 1;
			break;
		}
	} while ((rc = errno) == EINTR);
	return rc;
313
314
}

315
316
#define mdb_mutex_consistent(mutex)	0

Howard Chu's avatar
Howard Chu committed
317
#else
Hallvard Furuseth's avatar
Hallvard Furuseth committed
318
	/** Pointer/HANDLE type of shared mutex/semaphore.
Howard Chu's avatar
Howard Chu committed
319
	 */
320
typedef pthread_mutex_t mdb_mutex_t;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
321
	/** Mutex for the reader table (rw = r) or write transaction (rw = w).
Howard Chu's avatar
Howard Chu committed
322
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
323
324
325
#define MDB_MUTEX(env, rw)	(&(env)->me_txns->mti_##rw##mutex)
	/** Lock the reader or writer mutex.
	 *	Returns 0 or a code to give #mdb_mutex_failed(), as in #LOCK_MUTEX().
Howard Chu's avatar
Howard Chu committed
326
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
327
328
#define LOCK_MUTEX0(mutex)	pthread_mutex_lock(mutex)
	/** Unlock the reader or writer mutex.
Howard Chu's avatar
Howard Chu committed
329
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
330
#define UNLOCK_MUTEX(mutex)	pthread_mutex_unlock(mutex)
331
332
333
	/** Mark mutex-protected data as repaired, after death of previous owner.
	 */
#define mdb_mutex_consistent(mutex)	pthread_mutex_consistent(mutex)
334
#endif	/* MDB_USE_SYSV_SEM */
Howard Chu's avatar
Howard Chu committed
335
336
337

	/** Get the error code for the last failed system function.
	 */
Howard Chu's avatar
Howard Chu committed
338
#define	ErrCode()	errno
Howard Chu's avatar
Howard Chu committed
339

340
341
342
343
344
345
	/** An abstraction for a file handle.
	 *	On POSIX systems file handles are small integers. On Windows
	 *	they're opaque pointers.
	 */
#define	HANDLE	int

Howard Chu's avatar
Howard Chu committed
346
347
348
349
	/**	A value for an invalid file handle.
	 *	Mainly used to initialize file variables and signify that they are
	 *	unused.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
350
#define INVALID_HANDLE_VALUE	(-1)
Howard Chu's avatar
Howard Chu committed
351
352
353
354
355

	/** Get the size of a memory page for the system.
	 *	This is the basic size that the platform's memory manager uses, and is
	 *	fundamental to the use of memory-mapped files.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
356
#define	GET_PAGESIZE(x)	((x) = sysconf(_SC_PAGE_SIZE))
Howard Chu's avatar
Howard Chu committed
357
#endif
Howard Chu's avatar
Howard Chu committed
358

359
#if defined(_WIN32)
Howard Chu's avatar
Howard Chu committed
360
#define MNAME_LEN	32
361
#elif defined(MDB_USE_SYSV_SEM)
362
#define MNAME_LEN	(sizeof(int))
363
364
#else
#define MNAME_LEN	(sizeof(pthread_mutex_t))
Howard Chu's avatar
Howard Chu committed
365
366
#endif

367
368
369
370
371
372
#ifdef MDB_USE_SYSV_SEM
#define SYSV_SEM_FLAG	1		/**< SysV sems in lockfile format */
#else
#define SYSV_SEM_FLAG	0
#endif

373
/** @} */
Howard Chu's avatar
Howard Chu committed
374

Hallvard Furuseth's avatar
Hallvard Furuseth committed
375
376
377
378
379
380
381
#ifdef MDB_ROBUST_SUPPORTED
	/** Lock mutex, handle any error, set rc = result.
	 *	Return 0 on success, nonzero (not rc) on error.
	 */
#define LOCK_MUTEX(rc, env, mutex) \
	(((rc) = LOCK_MUTEX0(mutex)) && \
	 ((rc) = mdb_mutex_failed(env, mutex, rc)))
382
static int mdb_mutex_failed(MDB_env *env, mdb_mutex_t *mutex, int rc);
Hallvard Furuseth's avatar
Hallvard Furuseth committed
383
384
385
386
387
#else
#define LOCK_MUTEX(rc, env, mutex) ((rc) = LOCK_MUTEX0(mutex))
#define mdb_mutex_failed(env, mutex, rc) (rc)
#endif

388
#ifndef _WIN32
Howard Chu's avatar
Howard Chu committed
389
390
391
392
393
394
/**	A flag for opening a file and requesting synchronous data writes.
 *	This is only used when writing a meta page. It's not strictly needed;
 *	we could just do a normal write and then immediately perform a flush.
 *	But if this flag is available it saves us an extra system call.
 *
 *	@note If O_DSYNC is undefined but exists in /usr/include,
Hallvard Furuseth's avatar
Hallvard Furuseth committed
395
396
397
398
399
400
 * preferably set some compiler flag to get the definition.
 * Otherwise compile with the less efficient -DMDB_DSYNC=O_SYNC.
 */
#ifndef MDB_DSYNC
# define MDB_DSYNC	O_DSYNC
#endif
401
402
403
404
405
406
407
#endif

/** Function for flushing the data of a file. Define this to fsync
 *	if fdatasync() is not supported.
 */
#ifndef MDB_FDATASYNC
# define MDB_FDATASYNC	fdatasync
408
409
410
411
412
413
414
415
416
417
418
419
#endif

#ifndef MDB_MSYNC
# define MDB_MSYNC(addr,len,flags)	msync(addr,len,flags)
#endif

#ifndef MS_SYNC
#define	MS_SYNC	1
#endif

#ifndef MS_ASYNC
#define	MS_ASYNC	0
420
421
#endif

Howard Chu's avatar
Howard Chu committed
422
423
424
425
426
427
428
429
	/** A page number in the database.
	 *	Note that 64 bit page numbers are overkill, since pages themselves
	 *	already represent 12-13 bits of addressable memory, and the OS will
	 *	always limit applications to a maximum of 63 bits of address space.
	 *
	 *	@note In the #MDB_node structure, we only store 48 bits of this value,
	 *	which thus limits us to only 60 bits of addressable data.
	 */
430
typedef MDB_ID	pgno_t;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
431

432
433
434
	/** A transaction ID.
	 *	See struct MDB_txn.mt_txnid for details.
	 */
435
typedef MDB_ID	txnid_t;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
436

Howard Chu's avatar
Howard Chu committed
437
438
439
/** @defgroup debug	Debug Macros
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
440
#ifndef MDB_DEBUG
441
	/**	Enable debug output.  Needs variable argument macros (a C99 feature).
Howard Chu's avatar
Howard Chu committed
442
443
444
	 *	Set this to 1 for copious tracing. Set to 2 to add dumps of all IDLs
	 *	read from and written to the database (used for free space management).
	 */
Howard Chu's avatar
Howard Chu committed
445
#define MDB_DEBUG 0
446
#endif
Howard Chu's avatar
Howard Chu committed
447

448
#if MDB_DEBUG
449
static int mdb_debug;
450
static txnid_t mdb_debug_start;
451

452
453
454
455
456
	/**	Print a debug message with printf formatting.
	 *	Requires double parenthesis around 2 or more args.
	 */
# define DPRINTF(args) ((void) ((mdb_debug) && DPRINTF0 args))
# define DPRINTF0(fmt, ...) \
Hallvard Furuseth's avatar
Hallvard Furuseth committed
457
	fprintf(stderr, "%s:%d " fmt "\n", mdb_func_, __LINE__, __VA_ARGS__)
Howard Chu's avatar
Howard Chu committed
458
#else
459
# define DPRINTF(args)	((void) 0)
Howard Chu's avatar
Howard Chu committed
460
#endif
Howard Chu's avatar
Howard Chu committed
461
462
463
	/**	Print a debug string.
	 *	The string is printed literally, with no format processing.
	 */
464
#define DPUTS(arg)	DPRINTF(("%s", arg))
465
466
467
	/** Debuging output value of a cursor DBI: Negative in a sub-cursor. */
#define DDBI(mc) \
	(((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
Howard Chu's avatar
Howard Chu committed
468
/** @} */
Howard Chu's avatar
Howard Chu committed
469

470
471
	/**	@brief The maximum size of a database page.
	 *
Hallvard Furuseth's avatar
Hallvard Furuseth committed
472
473
	 *	It is 32k or 64k, since value-PAGEBASE must fit in
	 *	#MDB_page.%mp_upper.
474
475
476
477
	 *
	 *	LMDB will use database pages < OS pages if needed.
	 *	That causes more I/O in write transactions: The OS must
	 *	know (read) the whole page before writing a partial page.
Howard Chu's avatar
Howard Chu committed
478
479
480
481
482
483
484
485
	 *
	 *	Note that we don't currently support Huge pages. On Linux,
	 *	regular data files cannot use Huge pages, and in general
	 *	Huge pages aren't actually pageable. We rely on the OS
	 *	demand-pager to read our data and page it out when memory
	 *	pressure from other processes is high. So until OSs have
	 *	actual paging support for Huge pages, they're not viable.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
486
#define MAX_PAGESIZE	 (PAGEBASE ? 0x10000 : 0x8000)
Howard Chu's avatar
Howard Chu committed
487
488
489
490
491
492
493
494
495
496
497
498
499

	/** The minimum number of keys required in a database page.
	 *	Setting this to a larger value will place a smaller bound on the
	 *	maximum size of a data item. Data items larger than this size will
	 *	be pushed into overflow pages instead of being stored directly in
	 *	the B-tree node. This value used to default to 4. With a page size
	 *	of 4096 bytes that meant that any item larger than 1024 bytes would
	 *	go into an overflow page. That also meant that on average 2-3KB of
	 *	each overflow page was wasted space. The value cannot be lower than
	 *	2 because then there would no longer be a tree structure. With this
	 *	value, items larger than 2KB will go into overflow pages, and on
	 *	average only 1KB will be wasted.
	 */
Howard Chu's avatar
Howard Chu committed
500
#define MDB_MINKEYS	 2
Howard Chu's avatar
Howard Chu committed
501

Howard Chu's avatar
Howard Chu committed
502
	/**	A stamp that identifies a file as an LMDB file.
Howard Chu's avatar
Howard Chu committed
503
504
505
	 *	There's nothing special about this value other than that it is easily
	 *	recognizable, and it will reflect any byte order mismatches.
	 */
Howard Chu's avatar
Howard Chu committed
506
#define MDB_MAGIC	 0xBEEFC0DE
Howard Chu's avatar
Howard Chu committed
507

508
	/**	The version number for a database's datafile format. */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
509
#define MDB_DATA_VERSION	 ((MDB_DEVEL) ? 999 : 1)
510
	/**	The version number for a database's lockfile format. */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
511
#define MDB_LOCK_VERSION	 ((MDB_DEVEL) ? 999 : 1)
Howard Chu's avatar
Howard Chu committed
512

513
	/**	@brief The max size of a key we can write, or 0 for computed max.
514
	 *
515
516
517
518
519
520
521
522
523
	 *	This macro should normally be left alone or set to 0.
	 *	Note that a database with big keys or dupsort data cannot be
	 *	reliably modified by a liblmdb which uses a smaller max.
	 *	The default is 511 for backwards compat, or 0 when #MDB_DEVEL.
	 *
	 *	Other values are allowed, for backwards compat.  However:
	 *	A value bigger than the computed max can break if you do not
	 *	know what you are doing, and liblmdb <= 0.9.10 can break when
	 *	modifying a DB with keys/dupsort data bigger than its max.
524
	 *
525
526
527
	 *	Data items in an #MDB_DUPSORT database are also limited to
	 *	this size, since they're actually keys of a sub-DB.  Keys and
	 *	#MDB_DUPSORT data items must fit on a node in a regular page.
Howard Chu's avatar
Howard Chu committed
528
	 */
529
#ifndef MDB_MAXKEYSIZE
530
#define MDB_MAXKEYSIZE	 ((MDB_DEVEL) ? 0 : 511)
531
532
533
534
535
536
537
#endif

	/**	The maximum size of a key we can write to the environment. */
#if MDB_MAXKEYSIZE
#define ENV_MAXKEY(env)	(MDB_MAXKEYSIZE)
#else
#define ENV_MAXKEY(env)	((env)->me_maxkey)
538
#endif
Howard Chu's avatar
Howard Chu committed
539

540
541
542
543
544
545
	/**	@brief The maximum size of a data item.
	 *
	 *	We only store a 32 bit value for node sizes.
	 */
#define MAXDATASIZE	0xffffffffUL

Howard Chu's avatar
Howard Chu committed
546
#if MDB_DEBUG
547
548
549
550
	/**	Key size which fits in a #DKBUF.
	 *	@ingroup debug
	 */
#define DKBUF_MAXKEYSIZE ((MDB_MAXKEYSIZE) > 0 ? (MDB_MAXKEYSIZE) : 511)
Howard Chu's avatar
Howard Chu committed
551
552
553
554
	/**	A key buffer.
	 *	@ingroup debug
	 *	This is used for printing a hex dump of a key's contents.
	 */
555
#define DKBUF	char kbuf[DKBUF_MAXKEYSIZE*2+1]
Howard Chu's avatar
Howard Chu committed
556
557
558
559
	/**	Display a key in hex.
	 *	@ingroup debug
	 *	Invoke a function to display a key in hex.
	 */
Howard Chu's avatar
Howard Chu committed
560
561
#define	DKEY(x)	mdb_dkey(x, kbuf)
#else
Howard Chu's avatar
Howard Chu committed
562
#define	DKBUF
Howard Chu's avatar
Howard Chu committed
563
#define DKEY(x)	0
Howard Chu's avatar
Howard Chu committed
564
#endif
Howard Chu's avatar
Howard Chu committed
565

Howard Chu's avatar
Howard Chu committed
566
567
568
	/** An invalid page number.
	 *	Mainly used to denote an empty tree.
	 */
569
#define P_INVALID	 (~(pgno_t)0)
Howard Chu's avatar
Howard Chu committed
570

571
	/** Test if the flags \b f are set in a flag word \b w. */
Howard Chu's avatar
Howard Chu committed
572
573
#define F_ISSET(w, f)	 (((w) & (f)) == (f))

574
575
576
	/** Round \b n up to an even number. */
#define EVEN(n)		(((n) + 1U) & -2) /* sign-extending -2 to match n+1U */

Howard Chu's avatar
Howard Chu committed
577
578
579
580
	/**	Used for offsets within a single page.
	 *	Since memory pages are typically 4 or 8KB in size, 12-13 bits,
	 *	this is plenty.
	 */
Howard Chu's avatar
Howard Chu committed
581
582
typedef uint16_t	 indx_t;

Howard Chu's avatar
Howard Chu committed
583
584
585
586
	/**	Default size of memory map.
	 *	This is certainly too small for any actual applications. Apps should always set
	 *	the size explicitly using #mdb_env_set_mapsize().
	 */
Howard Chu's avatar
Howard Chu committed
587
588
#define DEFAULT_MAPSIZE	1048576

Howard Chu's avatar
Howard Chu committed
589
590
591
592
593
594
595
/**	@defgroup readers	Reader Lock Table
 *	Readers don't acquire any locks for their data access. Instead, they
 *	simply record their transaction ID in the reader table. The reader
 *	mutex is needed just to find an empty slot in the reader table. The
 *	slot's address is saved in thread-specific data so that subsequent read
 *	transactions started by the same thread need no further locking to proceed.
 *
Howard Chu's avatar
Howard Chu committed
596
597
 *	If #MDB_NOTLS is set, the slot address is not saved in thread-specific data.
 *
Howard Chu's avatar
Howard Chu committed
598
599
 *	No reader table is used if the database is on a read-only filesystem, or
 *	if #MDB_NOLOCK is set.
600
 *
Howard Chu's avatar
Howard Chu committed
601
602
603
 *	Since the database uses multi-version concurrency control, readers don't
 *	actually need any locking. This table is used to keep track of which
 *	readers are using data from which old transactions, so that we'll know
604
605
 *	when a particular old transaction is no longer in use. Old transactions
 *	that have discarded any data pages can then have those pages reclaimed
Howard Chu's avatar
Howard Chu committed
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
 *	for use by a later write transaction.
 *
 *	The lock table is constructed such that reader slots are aligned with the
 *	processor's cache line size. Any slot is only ever used by one thread.
 *	This alignment guarantees that there will be no contention or cache
 *	thrashing as threads update their own slot info, and also eliminates
 *	any need for locking when accessing a slot.
 *
 *	A writer thread will scan every slot in the table to determine the oldest
 *	outstanding reader transaction. Any freed pages older than this will be
 *	reclaimed by the writer. The writer doesn't use any locks when scanning
 *	this table. This means that there's no guarantee that the writer will
 *	see the most up-to-date reader info, but that's not required for correct
 *	operation - all we need is to know the upper bound on the oldest reader,
 *	we don't care at all about the newest reader. So the only consequence of
 *	reading stale information here is that old pages might hang around a
 *	while longer before being reclaimed. That's actually good anyway, because
 *	the longer we delay reclaiming old pages, the more likely it is that a
 *	string of contiguous pages can be found after coalescing old pages from
 *	many old transactions together.
 *	@{
 */
	/**	Number of slots in the reader table.
	 *	This value was chosen somewhat arbitrarily. 126 readers plus a
	 *	couple mutexes fit exactly into 8KB on my development machine.
	 *	Applications should set the table size using #mdb_env_set_maxreaders().
	 */
#define DEFAULT_READERS	126

	/**	The size of a CPU cache line in bytes. We want our lock structures
	 *	aligned to this size to avoid false cache line sharing in the
	 *	lock table.
	 *	This value works for most CPUs. For Itanium this should be 128.
	 */
Howard Chu's avatar
Howard Chu committed
640
#ifndef CACHELINE
Howard Chu's avatar
Howard Chu committed
641
#define CACHELINE	64
Howard Chu's avatar
Howard Chu committed
642
643
#endif

Howard Chu's avatar
Howard Chu committed
644
645
646
647
648
649
650
651
	/**	The information we store in a single slot of the reader table.
	 *	In addition to a transaction ID, we also record the process and
	 *	thread ID that owns a slot, so that we can detect stale information,
	 *	e.g. threads or processes that went away without cleaning up.
	 *	@note We currently don't check for stale records. We simply re-init
	 *	the table when we know that we're the only process opening the
	 *	lock file.
	 */
Howard Chu's avatar
Howard Chu committed
652
typedef struct MDB_rxbody {
653
	/**	Current Transaction ID when this transaction began, or (txnid_t)-1.
Howard Chu's avatar
Howard Chu committed
654
655
656
657
658
659
	 *	Multiple readers that start at the same time will probably have the
	 *	same ID here. Again, it's not important to exclude them from
	 *	anything; all we need to know is which version of the DB they
	 *	started from so we can avoid overwriting any data used in that
	 *	particular version.
	 */
660
	volatile txnid_t		mrb_txnid;
Howard Chu's avatar
Howard Chu committed
661
	/** The process ID of the process owning this reader txn. */
662
	volatile MDB_PID_T	mrb_pid;
Howard Chu's avatar
Howard Chu committed
663
	/** The thread ID of the thread owning this txn. */
664
	volatile MDB_THR_T	mrb_tid;
Howard Chu's avatar
Howard Chu committed
665
666
} MDB_rxbody;

Howard Chu's avatar
Howard Chu committed
667
	/** The actual reader record, with cacheline padding. */
Howard Chu's avatar
Howard Chu committed
668
typedef struct MDB_reader {
Howard Chu's avatar
Howard Chu committed
669
670
	union {
		MDB_rxbody mrx;
Howard Chu's avatar
Howard Chu committed
671
		/** shorthand for mrb_txnid */
Howard Chu's avatar
Howard Chu committed
672
673
674
#define	mr_txnid	mru.mrx.mrb_txnid
#define	mr_pid	mru.mrx.mrb_pid
#define	mr_tid	mru.mrx.mrb_tid
Howard Chu's avatar
Howard Chu committed
675
		/** cache line alignment */
Howard Chu's avatar
Howard Chu committed
676
677
		char pad[(sizeof(MDB_rxbody)+CACHELINE-1) & ~(CACHELINE-1)];
	} mru;
Howard Chu's avatar
Howard Chu committed
678
679
} MDB_reader;

Howard Chu's avatar
Howard Chu committed
680
681
682
683
684
685
686
	/** The header for the reader table.
	 *	The table resides in a memory-mapped file. (This is a different file
	 *	than is used for the main database.)
	 *
	 *	For POSIX the actual mutexes reside in the shared memory of this
	 *	mapped file. On Windows, mutexes are named objects allocated by the
	 *	kernel; we store the mutex names in this mapped file so that other
Howard Chu's avatar
Howard Chu committed
687
	 *	processes can grab them. This same approach is also used on
Howard Chu's avatar
Howard Chu committed
688
	 *	MacOSX/Darwin (using named semaphores) since MacOSX doesn't support
Howard Chu's avatar
Howard Chu committed
689
690
691
692
	 *	process-shared POSIX mutexes. For these cases where a named object
	 *	is used, the object name is derived from a 64 bit FNV hash of the
	 *	environment pathname. As such, naming collisions are extremely
	 *	unlikely. If a collision occurs, the results are unpredictable.
Howard Chu's avatar
Howard Chu committed
693
	 */
Howard Chu's avatar
Howard Chu committed
694
typedef struct MDB_txbody {
Howard Chu's avatar
Howard Chu committed
695
		/** Stamp identifying this as an LMDB file. It must be set
Howard Chu's avatar
Howard Chu committed
696
		 *	to #MDB_MAGIC. */
Howard Chu's avatar
Howard Chu committed
697
	uint32_t	mtb_magic;
698
699
		/** Format of this lock file. Must be set to #MDB_LOCK_FORMAT. */
	uint32_t	mtb_format;
700
#if defined(_WIN32)
Howard Chu's avatar
Howard Chu committed
701
	char	mtb_rmname[MNAME_LEN];
702
703
#elif defined(MDB_USE_SYSV_SEM)
	int 	mtb_semid;
704
	int		mtb_rlocked;
Howard Chu's avatar
Howard Chu committed
705
#else
Howard Chu's avatar
Howard Chu committed
706
		/** Mutex protecting access to this table.
Hallvard Furuseth's avatar
Hallvard Furuseth committed
707
		 *	This is the #MDB_MUTEX(env,r) reader table lock.
Howard Chu's avatar
Howard Chu committed
708
		 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
709
	pthread_mutex_t	mtb_rmutex;
Howard Chu's avatar
Howard Chu committed
710
#endif
Howard Chu's avatar
Howard Chu committed
711
712
713
714
		/**	The ID of the last transaction committed to the database.
		 *	This is recorded here only for convenience; the value can always
		 *	be determined by reading the main database meta pages.
		 */
715
	volatile txnid_t		mtb_txnid;
Howard Chu's avatar
Howard Chu committed
716
717
718
719
		/** The number of slots that have been used in the reader table.
		 *	This always records the maximum count, it is not decremented
		 *	when readers release their slots.
		 */
720
	volatile unsigned	mtb_numreaders;
Howard Chu's avatar
Howard Chu committed
721
722
} MDB_txbody;

Howard Chu's avatar
Howard Chu committed
723
	/** The actual reader table definition. */
Howard Chu's avatar
Howard Chu committed
724
typedef struct MDB_txninfo {
Howard Chu's avatar
Howard Chu committed
725
726
727
	union {
		MDB_txbody mtb;
#define mti_magic	mt1.mtb.mtb_magic
728
#define mti_format	mt1.mtb.mtb_format
Hallvard Furuseth's avatar
Hallvard Furuseth committed
729
#define mti_rmutex	mt1.mtb.mtb_rmutex
Howard Chu's avatar
Howard Chu committed
730
#define mti_rmname	mt1.mtb.mtb_rmname
Howard Chu's avatar
Howard Chu committed
731
732
#define mti_txnid	mt1.mtb.mtb_txnid
#define mti_numreaders	mt1.mtb.mtb_numreaders
733
734
#ifdef MDB_USE_SYSV_SEM
#define	mti_semid	mt1.mtb.mtb_semid
735
736
737
738
#define	mti_rlocked	mt1.mtb.mtb_rlocked
#endif
		char pad[(sizeof(MDB_txbody)+CACHELINE-1) & ~(CACHELINE-1)];
	} mt1;
Howard Chu's avatar
Howard Chu committed
739
	union {
740
#if defined(_WIN32)
Howard Chu's avatar
Howard Chu committed
741
		char mt2_wmname[MNAME_LEN];
Howard Chu's avatar
Howard Chu committed
742
#define	mti_wmname	mt2.mt2_wmname
743
744
745
#elif defined MDB_USE_SYSV_SEM
		int mt2_wlocked;
#define mti_wlocked	mt2.mt2_wlocked
Howard Chu's avatar
Howard Chu committed
746
#else
Howard Chu's avatar
Howard Chu committed
747
748
		pthread_mutex_t	mt2_wmutex;
#define mti_wmutex	mt2.mt2_wmutex
Howard Chu's avatar
Howard Chu committed
749
#endif
750
		char pad[(MNAME_LEN+CACHELINE-1) & ~(CACHELINE-1)];
Howard Chu's avatar
Howard Chu committed
751
752
	} mt2;
	MDB_reader	mti_readers[1];
Howard Chu's avatar
Howard Chu committed
753
} MDB_txninfo;
754
755
756
757
758
759

	/** Lockfile format signature: version, features and field layout */
#define MDB_LOCK_FORMAT \
	((uint32_t) \
	 ((MDB_LOCK_VERSION) \
	  /* Flags which describe functionality */ \
760
	  + (SYSV_SEM_FLAG << 18) \
761
	  + (((MDB_PIDLOCK) != 0) << 16)))
Howard Chu's avatar
Howard Chu committed
762
/** @} */
Howard Chu's avatar
Howard Chu committed
763

Howard Chu's avatar
Howard Chu committed
764
/** Common header for all page types.
Howard Chu's avatar
Howard Chu committed
765
 * Overflow records occupy a number of contiguous pages with no
Howard Chu's avatar
Howard Chu committed
766
767
 * headers on any page after the first.
 */
Howard Chu's avatar
Howard Chu committed
768
typedef struct MDB_page {
769
770
#define	mp_pgno	mp_p.p_pgno
#define	mp_next	mp_p.p_next
Howard Chu's avatar
Howard Chu committed
771
	union {
772
		pgno_t		p_pgno;	/**< page number */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
773
		struct MDB_page *p_next; /**< for in-memory list of freed pages */
774
	} mp_p;
Howard Chu's avatar
Howard Chu committed
775
	uint16_t	mp_pad;
Howard Chu's avatar
Howard Chu committed
776
777
778
779
780
/**	@defgroup mdb_page	Page Flags
 *	@ingroup internal
 *	Flags for the page headers.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
781
782
783
784
#define	P_BRANCH	 0x01		/**< branch page */
#define	P_LEAF		 0x02		/**< leaf page */
#define	P_OVERFLOW	 0x04		/**< overflow page */
#define	P_META		 0x08		/**< meta page */
785
#define	P_DIRTY		 0x10		/**< dirty page, also set for #P_SUBP pages */
Howard Chu's avatar
Howard Chu committed
786
#define	P_LEAF2		 0x20		/**< for #MDB_DUPFIXED records */
Howard Chu's avatar
Howard Chu committed
787
#define	P_SUBP		 0x40		/**< for #MDB_DUPSORT sub-pages */
Howard Chu's avatar
Howard Chu committed
788
#define	P_LOOSE		 0x4000		/**< page was dirtied then freed, can be reused */
Howard Chu's avatar
Howard Chu committed
789
#define	P_KEEP		 0x8000		/**< leave this page alone during spill */
Howard Chu's avatar
Howard Chu committed
790
/** @} */
Howard Chu's avatar
Howard Chu committed
791
	uint16_t	mp_flags;		/**< @ref mdb_page */
792
793
794
#define mp_lower	mp_pb.pb.pb_lower
#define mp_upper	mp_pb.pb.pb_upper
#define mp_pages	mp_pb.pb_pages
Howard Chu's avatar
Howard Chu committed
795
	union {
Howard Chu's avatar
Howard Chu committed
796
		struct {
797
798
799
800
801
			indx_t		pb_lower;		/**< lower bound of free space */
			indx_t		pb_upper;		/**< upper bound of free space */
		} pb;
		uint32_t	pb_pages;	/**< number of overflow pages */
	} mp_pb;
Howard Chu's avatar
Howard Chu committed
802
	indx_t		mp_ptrs[1];		/**< dynamic size */
Howard Chu's avatar
Howard Chu committed
803
804
} MDB_page;

Howard Chu's avatar
Howard Chu committed
805
	/** Size of the page header, excluding dynamic data at the end */
806
#define PAGEHDRSZ	 ((unsigned) offsetof(MDB_page, mp_ptrs))
Howard Chu's avatar
Howard Chu committed
807

Howard Chu's avatar
Howard Chu committed
808
809
810
	/** Address of first usable data byte in a page, after the header */
#define METADATA(p)	 ((void *)((char *)(p) + PAGEHDRSZ))

811
	/** ITS#7713, change PAGEBASE to handle 65536 byte pages */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
812
#define	PAGEBASE	((MDB_DEVEL) ? PAGEHDRSZ : 0)
813

Howard Chu's avatar
Howard Chu committed
814
	/** Number of nodes on a page */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
815
#define NUMKEYS(p)	 (((p)->mp_lower - (PAGEHDRSZ-PAGEBASE)) >> 1)
Howard Chu's avatar
Howard Chu committed
816
817

	/** The amount of space remaining in the page */
Howard Chu's avatar
Howard Chu committed
818
#define SIZELEFT(p)	 (indx_t)((p)->mp_upper - (p)->mp_lower)
Howard Chu's avatar
Howard Chu committed
819
820

	/** The percentage of space used in the page, in tenths of a percent. */
Howard Chu's avatar
Howard Chu committed
821
822
#define PAGEFILL(env, p) (1000L * ((env)->me_psize - PAGEHDRSZ - SIZELEFT(p)) / \
				((env)->me_psize - PAGEHDRSZ))
Howard Chu's avatar
Howard Chu committed
823
824
825
826
827
828
	/** The minimum page fill factor, in tenths of a percent.
	 *	Pages emptier than this are candidates for merging.
	 */
#define FILL_THRESHOLD	 250

	/** Test if a page is a leaf page */
Howard Chu's avatar
Howard Chu committed
829
#define IS_LEAF(p)	 F_ISSET((p)->mp_flags, P_LEAF)
Howard Chu's avatar
Howard Chu committed
830
	/** Test if a page is a LEAF2 page */
Howard Chu's avatar
Howard Chu committed
831
#define IS_LEAF2(p)	 F_ISSET((p)->mp_flags, P_LEAF2)
Howard Chu's avatar
Howard Chu committed
832
	/** Test if a page is a branch page */
Howard Chu's avatar
Howard Chu committed
833
#define IS_BRANCH(p)	 F_ISSET((p)->mp_flags, P_BRANCH)
Howard Chu's avatar
Howard Chu committed
834
	/** Test if a page is an overflow page */
Howard Chu's avatar
Howard Chu committed
835
#define IS_OVERFLOW(p)	 F_ISSET((p)->mp_flags, P_OVERFLOW)
Howard Chu's avatar
Howard Chu committed
836
837
	/** Test if a page is a sub page */
#define IS_SUBP(p)	 F_ISSET((p)->mp_flags, P_SUBP)
Howard Chu's avatar
Howard Chu committed
838

Howard Chu's avatar
Howard Chu committed
839
	/** The number of overflow pages needed to store the given size. */
840
#define OVPAGES(size, psize)	((PAGEHDRSZ-1 + (size)) / (psize) + 1)
Howard Chu's avatar
Howard Chu committed
841

842
	/** Link in #MDB_txn.%mt_loose_pgs list */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
843
#define NEXT_LOOSE_PAGE(p)		(*(MDB_page **)((p) + 2))
844

Howard Chu's avatar
Howard Chu committed
845
	/** Header for a single key/data pair within a page.
846
847
	 * Used in pages of type #P_BRANCH and #P_LEAF without #P_LEAF2.
	 * We guarantee 2-byte alignment for 'MDB_node's.
Howard Chu's avatar
Howard Chu committed
848
849
850
851
	 */
typedef struct MDB_node {
	/** lo and hi are used for data size on leaf nodes and for
	 * child pgno on branch nodes. On 64 bit platforms, flags
852
	 * is also used for pgno. (Branch nodes have no flags).
Howard Chu's avatar
Howard Chu committed
853
	 * They are in host byte order in case that lets some
854
	 * accesses be optimized into a 32-bit word access.
Howard Chu's avatar
Howard Chu committed
855
	 */
856
857
858
859
860
#if BYTE_ORDER == LITTLE_ENDIAN
	unsigned short	mn_lo, mn_hi;	/**< part of data size or pgno */
#else
	unsigned short	mn_hi, mn_lo;
#endif
Howard Chu's avatar
Howard Chu committed
861
862
863
864
865
/** @defgroup mdb_node Node Flags
 *	@ingroup internal
 *	Flags for node headers.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
866
867
868
#define F_BIGDATA	 0x01			/**< data put on overflow page */
#define F_SUBDATA	 0x02			/**< data is a sub-database */
#define F_DUPDATA	 0x04			/**< data has duplicates */
Howard Chu's avatar
Howard Chu committed
869
870

/** valid flags for #mdb_node_add() */
871
#define	NODE_ADD_FLAGS	(F_DUPDATA|F_SUBDATA|MDB_RESERVE|MDB_APPEND)
Howard Chu's avatar
Howard Chu committed
872

Howard Chu's avatar
Howard Chu committed
873
874
/** @} */
	unsigned short	mn_flags;		/**< @ref mdb_node */
Howard Chu's avatar
Howard Chu committed
875
876
877
878
879
880
881
	unsigned short	mn_ksize;		/**< key size */
	char		mn_data[1];			/**< key and data are appended here */
} MDB_node;

	/** Size of the node header, excluding dynamic data at the end */
#define NODESIZE	 offsetof(MDB_node, mn_data)

882
883
884
	/** Bit position of top word in page number, for shifting mn_flags */
#define PGNO_TOPWORD ((pgno_t)-1 > 0xffffffffu ? 32 : 0)

Howard Chu's avatar
Howard Chu committed
885
	/** Size of a node in a branch page with a given key.
Howard Chu's avatar
Howard Chu committed
886
887
888
889
	 *	This is just the node header plus the key, there is no data.
	 */
#define INDXSIZE(k)	 (NODESIZE + ((k) == NULL ? 0 : (k)->mv_size))

Howard Chu's avatar
Howard Chu committed
890
	/** Size of a node in a leaf page with a given key and data.
Howard Chu's avatar
Howard Chu committed
891
892
893
894
	 *	This is node header plus key plus data size.
	 */
#define LEAFSIZE(k, d)	 (NODESIZE + (k)->mv_size + (d)->mv_size)

Howard Chu's avatar
Howard Chu committed
895
	/** Address of node \b i in page \b p */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
896
#define NODEPTR(p, i)	 ((MDB_node *)((char *)(p) + (p)->mp_ptrs[i] + PAGEBASE))
Howard Chu's avatar
Howard Chu committed
897
898
899
900
901
902
903
904

	/** Address of the key for the node */
#define NODEKEY(node)	 (void *)((node)->mn_data)

	/** Address of the data for a node */
#define NODEDATA(node)	 (void *)((char *)(node)->mn_data + (node)->mn_ksize)

	/** Get the page number pointed to by a branch node */
905
906
907
#define NODEPGNO(node) \
	((node)->mn_lo | ((pgno_t) (node)->mn_hi << 16) | \
	 (PGNO_TOPWORD ? ((pgno_t) (node)->mn_flags << PGNO_TOPWORD) : 0))
Howard Chu's avatar
Howard Chu committed
908
909
910
	/** Set the page number in a branch node */
#define SETPGNO(node,pgno)	do { \
	(node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16; \
911
	if (PGNO_TOPWORD) (node)->mn_flags = (pgno) >> PGNO_TOPWORD; } while(0)
Howard Chu's avatar
Howard Chu committed
912
913
914
915
916
917
918
919
920

	/** Get the size of the data in a leaf node */
#define NODEDSZ(node)	 ((node)->mn_lo | ((unsigned)(node)->mn_hi << 16))
	/** Set the size of the data for a leaf node */
#define SETDSZ(node,size)	do { \
	(node)->mn_lo = (size) & 0xffff; (node)->mn_hi = (size) >> 16;} while(0)
	/** The size of a key in a node */
#define NODEKSZ(node)	 ((node)->mn_ksize)

Howard Chu's avatar
Howard Chu committed
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
	/** Copy a page number from src to dst */
#ifdef MISALIGNED_OK
#define COPY_PGNO(dst,src)	dst = src
#else
#if SIZE_MAX > 4294967295UL
#define COPY_PGNO(dst,src)	do { \
	unsigned short *s, *d;	\
	s = (unsigned short *)&(src);	\
	d = (unsigned short *)&(dst);	\
	*d++ = *s++;	\
	*d++ = *s++;	\
	*d++ = *s++;	\
	*d = *s;	\
} while (0)
#else
#define COPY_PGNO(dst,src)	do { \
	unsigned short *s, *d;	\
	s = (unsigned short *)&(src);	\
	d = (unsigned short *)&(dst);	\
	*d++ = *s++;	\
	*d = *s;	\
} while (0)
#endif
#endif
Howard Chu's avatar
Howard Chu committed
945
946
947
948
949
950
	/** The address of a key in a LEAF2 page.
	 *	LEAF2 pages are used for #MDB_DUPFIXED sorted-duplicate sub-DBs.
	 *	There are no node headers, keys are stored contiguously.
	 */
#define LEAF2KEY(p, i, ks)	((char *)(p) + PAGEHDRSZ + ((i)*(ks)))

Howard Chu's avatar
Howard Chu committed
951
952
953
954
955
956
	/** Set the \b node's key into \b keyptr, if requested. */
#define MDB_GET_KEY(node, keyptr)	{ if ((keyptr) != NULL) { \
	(keyptr)->mv_size = NODEKSZ(node); (keyptr)->mv_data = NODEKEY(node); } }

	/** Set the \b node's key into \b key. */
#define MDB_GET_KEY2(node, key)	{ key.mv_size = NODEKSZ(node); key.mv_data = NODEKEY(node); }
Howard Chu's avatar
Howard Chu committed
957
958

	/** Information about a single database in the environment. */
Howard Chu's avatar
Howard Chu committed
959
typedef struct MDB_db {
Howard Chu's avatar
Howard Chu committed
960
	uint32_t	md_pad;		/**< also ksize for LEAF2 pages */
961
	uint16_t	md_flags;	/**< @ref mdb_dbi_open */
Howard Chu's avatar
Howard Chu committed
962
	uint16_t	md_depth;	/**< depth of this tree */
963
964
965
966
	pgno_t		md_branch_pages;	/**< number of internal pages */
	pgno_t		md_leaf_pages;		/**< number of leaf pages */
	pgno_t		md_overflow_pages;	/**< number of overflow pages */
	size_t		md_entries;		/**< number of data items */
Howard Chu's avatar
Howard Chu committed
967
	pgno_t		md_root;		/**< the root page of this tree */
Howard Chu's avatar
Howard Chu committed
968
969
} MDB_db;

970
	/** mdb_dbi_open flags */
971
972
#define MDB_VALID	0x8000		/**< DB handle is valid, for me_dbflags */
#define PERSISTENT_FLAGS	(0xffff & ~(MDB_VALID))
973
974
975
#define VALID_FLAGS	(MDB_REVERSEKEY|MDB_DUPSORT|MDB_INTEGERKEY|MDB_DUPFIXED|\
	MDB_INTEGERDUP|MDB_REVERSEDUP|MDB_CREATE)

Howard Chu's avatar
Howard Chu committed
976
	/** Handle for the DB used to track free pages. */
Howard Chu's avatar
Howard Chu committed
977
#define	FREE_DBI	0
Howard Chu's avatar
Howard Chu committed
978
	/** Handle for the default DB. */
Howard Chu's avatar
Howard Chu committed
979
980
#define	MAIN_DBI	1

981
982
983
984
	/** Meta page content.
	 *	A meta page is the start point for accessing a database snapshot.
	 *	Pages 0-1 are meta pages. Transaction N writes meta page #(N % 2).
	 */
Howard Chu's avatar
Howard Chu committed
985
typedef struct MDB_meta {
Howard Chu's avatar
Howard Chu committed
986
		/** Stamp identifying this as an LMDB file. It must be set
Howard Chu's avatar
Howard Chu committed
987
		 *	to #MDB_MAGIC. */
Howard Chu's avatar
Howard Chu committed
988
	uint32_t	mm_magic;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
989
		/** Version number of this file. Must be set to #MDB_DATA_VERSION. */
Howard Chu's avatar
Howard Chu committed
990
	uint32_t	mm_version;
Howard Chu's avatar
Howard Chu committed
991
992
993
994
	void		*mm_address;		/**< address for fixed mapping */
	size_t		mm_mapsize;			/**< size of mmap region */
	MDB_db		mm_dbs[2];			/**< first is free space, 2nd is main db */
	/** The size of pages used in this DB */
Howard Chu's avatar
Howard Chu committed
995
#define	mm_psize	mm_dbs[0].md_pad
Howard Chu's avatar
Howard Chu committed
996
	/** Any persistent environment flags. @ref mdb_env */
Howard Chu's avatar
Howard Chu committed
997
#define	mm_flags	mm_dbs[0].md_flags
Howard Chu's avatar
Howard Chu committed
998
	pgno_t		mm_last_pg;			/**< last used page in file */
999
	volatile txnid_t	mm_txnid;	/**< txnid that committed this page */
Howard Chu's avatar
Howard Chu committed
1000
1001
} MDB_meta;

1002
	/** Buffer for a stack-allocated meta page.
1003
1004
1005
1006
	 *	The members define size and alignment, and silence type
	 *	aliasing warnings.  They are not used directly; that could
	 *	mean incorrectly using several union members in parallel.
	 */
1007
typedef union MDB_metabuf {
1008
1009
1010
1011
1012
	MDB_page	mb_page;
	struct {
		char		mm_pad[PAGEHDRSZ];
		MDB_meta	mm_meta;
	} mb_metabuf;
1013
} MDB_metabuf;
1014

Howard Chu's avatar
Howard Chu committed
1015
1016
1017
1018
1019
1020
1021
1022
1023
	/** Auxiliary DB info.
	 *	The information here is mostly static/read-only. There is
	 *	only a single copy of this record in the environment.
	 */
typedef struct MDB_dbx {
	MDB_val		md_name;		/**< name of the database */
	MDB_cmp_func	*md_cmp;	/**< function for comparing keys */
	MDB_cmp_func	*md_dcmp;	/**< function for comparing data items */
	MDB_rel_func	*md_rel;	/**< user relocate function */
1024
	void		*md_relctx;		/**< user-provided context for md_rel */
Howard Chu's avatar
Howard Chu committed
1025
} MDB_dbx;
Howard Chu's avatar
Howard Chu committed
1026

Howard Chu's avatar
Howard Chu committed
1027
1028
1029
1030
	/** A database transaction.
	 *	Every operation requires a transaction handle.
	 */
struct MDB_txn {
1031
1032
	MDB_txn		*mt_parent;		/**< parent of a nested txn */
	MDB_txn		*mt_child;		/**< nested txn under this txn */
Howard Chu's avatar
Howard Chu committed
1033
1034
1035
1036
1037
	pgno_t		mt_next_pgno;	/**< next unallocated page */
	/** The ID of this transaction. IDs are integers incrementing from 1.
	 *	Only committed write transactions increment the ID. If a transaction
	 *	aborts, the ID may be re-used by the next writer.
	 */
1038
	txnid_t		mt_txnid;
Howard Chu's avatar
Howard Chu committed
1039
1040
1041
	MDB_env		*mt_env;		/**< the DB environment */
	/** The list of pages that became unused during this transaction.
	 */
1042
	MDB_IDL		mt_free_pgs;
Howard Chu's avatar
Howard Chu committed
1043
	/** The list of loose pages that became unused and may be reused
1044
	 *	in this transaction, linked through #NEXT_LOOSE_PAGE(page).
Howard Chu's avatar
Howard Chu committed
1045
1046
	 */
	MDB_page	*mt_loose_pgs;
1047
1048
	/* #Number of loose pages (#mt_loose_pgs) */
	int			mt_loose_count;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
1049
	/** The sorted list of dirty pages we temporarily wrote to disk
1050
1051
	 *	because the dirty list was full. page numbers in here are
	 *	shifted left by 1, deleted slots have the LSB set.
Howard Chu's avatar
Howard Chu committed
1052
1053
	 */
	MDB_IDL		mt_spill_pgs;
Howard Chu's avatar
Howard Chu committed
1054
	union {
Hallvard Furuseth's avatar
Hallvard Furuseth committed
1055
1056
1057
1058
		/** For write txns: Modified pages. Sorted when not MDB_WRITEMAP. */
		MDB_ID2L	dirty_list;
		/** For read txns: This thread/txn's reader table slot, or NULL. */
		MDB_reader	*reader;
Howard Chu's avatar
Howard Chu committed
1059
1060
1061
1062
1063
	} mt_u;
	/** Array of records for each DB known in the environment. */
	MDB_dbx		*mt_dbxs;
	/** Array of MDB_db records for each known DB */
	MDB_db		*mt_dbs;
1064
1065
	/** Array of sequence numbers for each DB handle */
	unsigned int	*mt_dbiseqs;
Howard Chu's avatar
Howard Chu committed
1066
1067
1068
1069
/** @defgroup mt_dbflag	Transaction DB Flags
 *	@ingroup internal
 * @{
 */
1070
#define DB_DIRTY	0x01		/**< DB was modified or is DUPSORT data */
1071
1072
#define DB_STALE	0x02		/**< Named-DB record is older than txnID */
#define DB_NEW		0x04		/**< Named-DB handle opened in this txn */
1073
#define DB_VALID	0x08		/**< DB handle is valid, see also #MDB_VALID */
Howard Chu's avatar
Howard Chu committed
1074
/** @} */
1075
	/** In write txns, array of cursors for each DB */
Howard Chu's avatar
Howard Chu committed
1076
	MDB_cursor	**mt_cursors;
Howard Chu's avatar
Howard Chu committed
1077
1078
	/** Array of flags for each DB */
	unsigned char	*mt_dbflags;
Howard Chu's avatar
Howard Chu committed
1079
1080
1081
	/**	Number of DB records in use. This number only ever increments;
	 *	we don't decrement it when individual DB handles are closed.
	 */
1082
	MDB_dbi		mt_numdbs;
Howard Chu's avatar
Howard Chu committed
1083

Howard Chu's avatar
Howard Chu committed
1084
1085
1086
1087
/** @defgroup mdb_txn	Transaction Flags
 *	@ingroup internal
 *	@{
 */
1088
1089
1090
1091
1092
1093
1094
	/** #mdb_txn_begin() flags */
#define MDB_TXN_BEGIN_FLAGS	(MDB_NOMETASYNC|MDB_NOSYNC|MDB_RDONLY)
#define MDB_TXN_NOMETASYNC	MDB_NOMETASYNC	/**< don't sync meta for this txn on commit */
#define MDB_TXN_NOSYNC		MDB_NOSYNC	/**< don't sync this txn on commit */
#define MDB_TXN_RDONLY		MDB_RDONLY	/**< read-only transaction */
	/* internal txn flags */
#define MDB_TXN_WRITEMAP	MDB_WRITEMAP	/**< copy of #MDB_env flag in writers */
1095
#define MDB_TXN_ERROR		0x02		/**< txn is unusable after an error */
1096
#define MDB_TXN_DIRTY		0x04		/**< must write, even if dirty list is empty */
Howard Chu's avatar
Howard Chu committed
1097
#define MDB_TXN_SPILLS		0x08		/**< txn or a parent has spilled pages */
Howard Chu's avatar
Howard Chu committed
1098
1099
/** @} */
	unsigned int	mt_flags;		/**< @ref mdb_txn */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
1100
	/** #dirty_list room: Array size - \#dirty pages visible to this txn.
1101
1102
1103
1104
	 *	Includes ancestor txns' dirty pages not hidden by other txns'
	 *	dirty/spilled pages. Thus commit(nested txn) has room to merge
	 *	dirty_list into mt_parent after freeing hidden mt_parent pages.
	 */
1105
	unsigned int	mt_dirty_room;
Howard Chu's avatar
Howard Chu committed
1106
};
Howard Chu's avatar
Howard Chu committed
1107

Howard Chu's avatar
Howard Chu committed
1108
/** Enough space for 2^32 nodes with minimum of 2 keys per node. I.e., plenty.
1109
1110
1111
 * At 4 keys per node, enough for 2^64 nodes, so there's probably no need to
 * raise this on a 64 bit machine.
 */
Howard Chu's avatar
Howard Chu committed
1112
#define CURSOR_STACK		 32
Howard Chu's avatar
Howard Chu committed
1113

Howard Chu's avatar
Howard Chu committed
1114
struct MDB_xcursor;
1115

1116
1117
1118
1119
1120
1121
1122
1123
	/** Cursors are used for all DB operations.
	 *	A cursor holds a path of (page pointer, key index) from the DB
	 *	root to a position in the DB, plus other state. #MDB_DUPSORT
	 *	cursors include an xcursor to the current data item. Write txns
	 *	track their cursors and keep them up to date when data moves.
	 *	Exception: An xcursor's pointer to a #P_SUBP page can be stale.
	 *	(A node with #F_DUPDATA but no #F_SUBDATA contains a subpage).
	 */
Howard Chu's avatar
Howard Chu committed
1124
struct MDB_cursor {
Howard Chu's avatar
Howard Chu committed
1125
1126
	/** Next cursor on this DB in this txn */
	MDB_cursor	*mc_next;
1127
1128
	/** Backup of the original cursor if this cursor is a shadow */
	MDB_cursor	*mc_backup;
Howard Chu's avatar
Howard Chu committed
1129
	/** Context used for databases with #MDB_DUPSORT, otherwise NULL */