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Revision 1.5 by root, Wed Dec 12 01:20:54 2007 UTC vs.
Revision 1.14 by root, Tue Oct 21 02:21:25 2008 UTC

… …
22 db_put $db, undef, "key", "data", 0, sub { 22 db_put $db, undef, "key", "data", 0, sub {
23 db_del $db, undef, "key"; 23 db_del $db, undef, "key";
24 }; 24 };
25 db_sync $db; 25 db_sync $db;
26 26
27 # automatic result processing with AnyEvent: 27 # when you also use Coro, management is easy:
28 our $FH; open $FH, "<&=" . BDB::poll_fileno; 28 use Coro::BDB;
29 our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb); 29
30 # automatic event loop intergration with AnyEvent:
31 use AnyEvent::BDB;
30 32
31 # automatic result processing with EV: 33 # automatic result processing with EV:
32 my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb; 34 my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
33 35
34 # with Glib: 36 # with Glib:
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84 Request has reached the end of its lifetime and holds no resources 86 Request has reached the end of its lifetime and holds no resources
85 anymore (except possibly for the Perl object, but its connection to 87 anymore (except possibly for the Perl object, but its connection to
86 the actual aio request is severed and calling its methods will 88 the actual aio request is severed and calling its methods will
87 either do nothing or result in a runtime error). 89 either do nothing or result in a runtime error).
88 90
89 BERKELEYDB FUNCTIONS 91BERKELEYDB FUNCTIONS
90 All of these are functions. The create functions simply return a new 92 All of these are functions. The create functions simply return a new
91 object and never block. All the remaining functions all take an optional 93 object and never block. All the remaining functions take an optional
92 callback as last argument. If it is missing, then the function will be 94 callback as last argument. If it is missing, then the function will be
93 executed synchronously. In both cases, $! will reflect the return value 95 executed synchronously. In both cases, $! will reflect the return value
94 of the function. 96 of the function.
95 97
96 BDB functions that cannot block (mostly functions that manipulate 98 BDB functions that cannot block (mostly functions that manipulate
97 settings) are method calls on the relevant objects, so the rule of thumb 99 settings) are method calls on the relevant objects, so the rule of thumb
98 is: if its a method, its not blocking, if its a function, it takes a 100 is: if it's a method, it's not blocking, if it's a function, it takes a
99 callback as last argument. 101 callback as last argument.
100 102
101 In the following, $int signifies an integer return value, "octetstring" 103 In the following, $int signifies an integer return value, "bdb_filename"
102 is a "binary string" (i.e. a perl string with no character indices 104 is a "filename" (octets on unix, madness on windows), "U32" is an
103 >255), "U32" is an unsigned 32 bit integer, "int" is some integer, "NV" 105 unsigned 32 bit integer, "int" is some integer, "NV" is a floating point
104 is a floating point value. 106 value.
105 107
106 The "SV *" types are generic perl scalars (for input and output of data 108 Most "SV *" types are generic perl scalars (for input and output of data
107 values), and the "SV *callback" is the optional callback function to 109 values).
108 call when the request is completed.
109 110
110 The various "DB_ENV" etc. arguments are handles return by 111 The various "DB_ENV" etc. arguments are handles return by
111 "db_env_create", "db_create", "txn_begin" and so on. If they have an 112 "db_env_create", "db_create", "txn_begin" and so on. If they have an
112 appended "_ornull" this means they are optional and you can pass "undef" 113 appended "_ornull" this means they are optional and you can pass "undef"
113 for them, resulting a NULL pointer on the C level. 114 for them, resulting a NULL pointer on the C level.
114 115
116 The "SV *callback" is the optional callback function to call when the
117 request is completed. This last callback argument is special: the
118 callback is simply the last argument passed. If there are "optional"
119 arguments before the callback they can be left out. The callback itself
120 can be left out or specified as "undef", in which case the function will
121 be executed synchronously.
122
123 For example, "db_env_txn_checkpoint" usually is called with all integer
124 arguments zero. These can be left out, so all of these specify a call to
125 "DB_ENV->txn_checkpoint", to be executed asynchronously with a callback
126 to be called:
127
128 db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
129 db_env_txn_checkpoint $db_env, 0, 0, sub { };
130 db_env_txn_checkpoint $db_env, sub { };
131
132 While these all specify a call to "DB_ENV->txn_checkpoint" to be
133 executed synchronously:
134
135 db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
136 db_env_txn_checkpoint $db_env, 0, 0, 0;
137 db_env_txn_checkpoint $db_env, 0;
138
115 BDB functions 139 BDB functions
116 Functions in the BDB namespace, exported by default: 140 Functions in the BDB namespace, exported by default:
117 141
118 $env = db_env_create (U32 env_flags = 0) 142 $env = db_env_create (U32 env_flags = 0)
119 flags: RPCCLIENT 143 flags: RPCCLIENT
120 144
121 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 145 db_env_open (DB_ENV *env, bdb_filename db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef)
122 open_flags: INIT_CDB INIT_LOCK INIT_LOG INIT_MPOOL INIT_REP INIT_TXN RECOVER RECOVER_FATAL USE_ENVIRON USE_ENVIRON_ROOT CREATE LOCKDOWN PRIVATE REGISTER SYSTEM_MEM 146 open_flags: INIT_CDB INIT_LOCK INIT_LOG INIT_MPOOL INIT_REP INIT_TXN RECOVER RECOVER_FATAL USE_ENVIRON USE_ENVIRON_ROOT CREATE LOCKDOWN PRIVATE REGISTER SYSTEM_MEM
123 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) 147 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef)
124 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 148 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
125 flags: FORCE 149 flags: FORCE
126 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) 150 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef)
127 atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST 151 atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
128 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) 152 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef)
129 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) 153 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef)
154 db_env_dbremove (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
155 db_env_dbrename (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = &PL_sv_undef)
156 db_env_log_archive (DB_ENV *env, SV *listp, U32 flags = 0, SV *callback = &PL_sv_undef)
130 157
131 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 158 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
132 flags: XA_CREATE 159 flags: XA_CREATE
133 160
134 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 161 db_open (DB *db, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
135 flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE 162 flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
136 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 163 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
137 flags: DB_NOSYNC 164 flags: DB_NOSYNC
138 db_upgrade (DB *db, octetstring file, U32 flags = 0, SV *callback = &PL_sv_undef) 165 db_upgrade (DB *db, bdb_filename file, U32 flags = 0, SV *callback = &PL_sv_undef)
139 db_compact (DB *db, DB_TXN_ornull *txn = 0, SV *start = 0, SV *stop = 0, SV *unused1 = 0, U32 flags = DB_FREE_SPACE, SV *unused2 = 0, SV *callback = &PL_sv_undef) 166 db_compact (DB *db, DB_TXN_ornull *txn = 0, SV *start = 0, SV *stop = 0, SV *unused1 = 0, U32 flags = DB_FREE_SPACE, SV *unused2 = 0, SV *callback = &PL_sv_undef)
140 flags: FREELIST_ONLY FREE_SPACE 167 flags: FREELIST_ONLY FREE_SPACE
141 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 168 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
142 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) 169 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
143 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 170 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
144 flags: APPEND NODUPDATA NOOVERWRITE 171 flags: APPEND NODUPDATA NOOVERWRITE
172 db_exists (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = 0) (v4.6)
145 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 173 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
146 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW 174 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
147 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 175 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
148 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW 176 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
149 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 177 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef)
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201 229
202 You can use the "$txn->failed" method to check wether a transaction has 230 You can use the "$txn->failed" method to check wether a transaction has
203 failed in this way and abort further processing (excluding 231 failed in this way and abort further processing (excluding
204 "db_txn_finish"). 232 "db_txn_finish").
205 233
206 DB_ENV/database environment methods 234 DB_ENV/database environment methods
207 Methods available on DB_ENV/$env handles: 235 Methods available on DB_ENV/$env handles:
208 236
209 DESTROY (DB_ENV_ornull *env) 237 DESTROY (DB_ENV_ornull *env)
210 CODE: 238 CODE:
211 if (env) 239 if (env)
… …
214 $int = $env->set_data_dir (const char *dir) 242 $int = $env->set_data_dir (const char *dir)
215 $int = $env->set_tmp_dir (const char *dir) 243 $int = $env->set_tmp_dir (const char *dir)
216 $int = $env->set_lg_dir (const char *dir) 244 $int = $env->set_lg_dir (const char *dir)
217 $int = $env->set_shm_key (long shm_key) 245 $int = $env->set_shm_key (long shm_key)
218 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 246 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
219 $int = $env->set_flags (U32 flags, int onoff) 247 $int = $env->set_flags (U32 flags, int onoff = 1)
248 $int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
249 $int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
220 $env->set_errfile (FILE *errfile = 0) 250 $env->set_errfile (FILE *errfile = 0)
221 $env->set_msgfile (FILE *msgfile = 0) 251 $env->set_msgfile (FILE *msgfile = 0)
222 $int = $env->set_verbose (U32 which, int onoff = 1) 252 $int = $env->set_verbose (U32 which, int onoff = 1)
223 $int = $env->set_encrypt (const char *password, U32 flags = 0) 253 $int = $env->set_encrypt (const char *password, U32 flags = 0)
224 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) 254 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
… …
236 $int = $env->mutex_set_max (U32 max) 266 $int = $env->mutex_set_max (U32 max)
237 $int = $env->mutex_set_align (U32 align) 267 $int = $env->mutex_set_align (U32 align)
238 268
239 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 269 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
240 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC 270 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
271 $txn = $env->cdsgroup_begin; (v4.5)
241 272
242 Example: 273 Example:
243 use AnyEvent; 274 use AnyEvent;
244 use BDB; 275 use BDB;
245 276
… …
257 BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE, 288 BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE,
258 0600; 289 0600;
259 290
260 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 291 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
261 292
262 DB/database methods 293 DB/database methods
263 Methods available on DB/$db handles: 294 Methods available on DB/$db handles:
264 295
265 DESTROY (DB_ornull *db) 296 DESTROY (DB_ornull *db)
266 CODE: 297 CODE:
267 if (db) 298 if (db)
… …
307 338
308 db_del $db, undef, "key $_" for 1..1000; 339 db_del $db, undef, "key $_" for 1..1000;
309 340
310 db_sync $db; 341 db_sync $db;
311 342
312 DB_TXN/transaction methods 343 DB_TXN/transaction methods
313 Methods available on DB_TXN/$txn handles: 344 Methods available on DB_TXN/$txn handles:
314 345
315 DESTROY (DB_TXN_ornull *txn) 346 DESTROY (DB_TXN_ornull *txn)
316 CODE: 347 CODE:
317 if (txn) 348 if (txn)
… …
321 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT 352 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
322 353
323 $bool = $txn->failed 354 $bool = $txn->failed
324 # see db_txn_finish documentation, above 355 # see db_txn_finish documentation, above
325 356
326 DBC/cursor methods 357 DBC/cursor methods
327 Methods available on DBC/$dbc handles: 358 Methods available on DBC/$dbc handles:
328 359
329 DESTROY (DBC_ornull *dbc) 360 DESTROY (DBC_ornull *dbc)
330 CODE: 361 CODE:
331 if (dbc) 362 if (dbc)
332 dbc->c_close (dbc); 363 dbc->c_close (dbc);
364
365 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
333 366
334 Example: 367 Example:
335 my $c = $db->cursor; 368 my $c = $db->cursor;
336 369
337 for (;;) { 370 for (;;) {
… …
340 last if $!; 373 last if $!;
341 } 374 }
342 375
343 db_c_close $c; 376 db_c_close $c;
344 377
345 DB_SEQUENCE/sequence methods 378 DB_SEQUENCE/sequence methods
346 Methods available on DB_SEQUENCE/$seq handles: 379 Methods available on DB_SEQUENCE/$seq handles:
347 380
348 DESTROY (DB_SEQUENCE_ornull *seq) 381 DESTROY (DB_SEQUENCE_ornull *seq)
349 CODE: 382 CODE:
350 if (seq) 383 if (seq)
… …
356 flags: SEQ_DEC SEQ_INC SEQ_WRAP 389 flags: SEQ_DEC SEQ_INC SEQ_WRAP
357 $int = $seq->set_range (db_seq_t min, db_seq_t max) 390 $int = $seq->set_range (db_seq_t min, db_seq_t max)
358 391
359 Example: 392 Example:
360 my $seq = $db->sequence; 393 my $seq = $db->sequence;
361 394
362 db_sequence_open $seq, undef, "seq", BDB::CREATE; 395 db_sequence_open $seq, undef, "seq", BDB::CREATE;
363 db_sequence_get $seq, undef, 1, my $value; 396 db_sequence_get $seq, undef, 1, my $value;
364 397
365 SUPPORT FUNCTIONS 398SUPPORT FUNCTIONS
366 EVENT PROCESSING AND EVENT LOOP INTEGRATION 399 EVENT PROCESSING AND EVENT LOOP INTEGRATION
367 $msg = BDB::strerror [$errno] 400 $msg = BDB::strerror [$errno]
368 Returns the string corresponding to the given errno value. If no 401 Returns the string corresponding to the given errno value. If no
369 argument is given, use $!. 402 argument is given, use $!.
403
404 Note that the BDB module also patches the $! variable directly, so
405 you should be able to get a bdb error string by simply stringifying
406 $!.
370 407
371 $fileno = BDB::poll_fileno 408 $fileno = BDB::poll_fileno
372 Return the *request result pipe file descriptor*. This filehandle 409 Return the *request result pipe file descriptor*. This filehandle
373 must be polled for reading by some mechanism outside this module 410 must be polled for reading by some mechanism outside this module
374 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 411 (e.g. Event or select, see below or the SYNOPSIS). If the pipe
… …
444 Strictly equivalent to: 481 Strictly equivalent to:
445 482
446 BDB::poll_wait, BDB::poll_cb 483 BDB::poll_wait, BDB::poll_cb
447 while BDB::nreqs; 484 while BDB::nreqs;
448 485
486 VERSION CHECKING
487 BerkeleyDB comes in various versions, many of them have minor
488 incompatibilities. This means that traditional "at least version x.x"
489 checks are often not sufficient.
490
491 Example: set the log_autoremove option in a way compatible with <v4.7
492 and v4.7. Note the use of & on the constants to avoid triggering a
493 compiletime bug when the symbol isn't available.
494
495 $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
496 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
497
498 BDB::VERSION
499 The "BDB::VERSION" function, when called without arguments, returns
500 the Berkeley DB version as a v-string (usually with 3 components).
501 You should use "lt" and "ge" operators exclusively to make
502 comparisons.
503
504 Example: check for at least version 4.7.
505
506 BDB::VERSION ge v4.7 or die;
507
508 BDB::VERSION min-version
509 Returns true if the BDB version is at least the given version
510 (specified as a v-string), false otherwise.
511
512 Example: check for at least version 4.5.
513
514 BDB::VERSION v4.7 or die;
515
516 BDB::VERSION min-version, max-version
517 Returns true of the BDB version is at least version "min-version"
518 (specify "undef" or "v0" for any minimum version) and less then
519 "max-version".
520
521 Example: check wether version is strictly less then v4.7.
522
523 BDB::VERSION v0, v4.7
524 or die "version 4.7 is not yet supported";
525
449 CONTROLLING THE NUMBER OF THREADS 526 CONTROLLING THE NUMBER OF THREADS
450 BDB::min_parallel $nthreads 527 BDB::min_parallel $nthreads
451 Set the minimum number of BDB threads to $nthreads. The current 528 Set the minimum number of BDB threads to $nthreads. The current
452 default is 8, which means eight asynchronous operations can execute 529 default is 8, which means eight asynchronous operations can execute
453 concurrently at any one time (the number of outstanding requests, 530 concurrently at any one time (the number of outstanding requests,
454 however, is unlimited). 531 however, is unlimited).
… …
513 You can still queue as many requests as you want. Therefore, 590 You can still queue as many requests as you want. Therefore,
514 "max_oustsanding" is mainly useful in simple scripts (with low 591 "max_oustsanding" is mainly useful in simple scripts (with low
515 values) or as a stop gap to shield against fatal memory overflow 592 values) or as a stop gap to shield against fatal memory overflow
516 (with large values). 593 (with large values).
517 594
518 BDB::set_sync_prepare $cb 595 $old_cb = BDB::set_sync_prepare $cb
519 Sets a callback that is called whenever a request is created without 596 Sets a callback that is called whenever a request is created without
520 an explicit callback. It has to return two code references. The 597 an explicit callback. It has to return two code references. The
521 first is used as the request callback, and the second is called to 598 first is used as the request callback (it should save the return
522 wait until the first callback has been called. The default 599 status), and the second is called to wait until the first callback
523 implementation works like this: 600 has been called (it must set $! to the return status).
601
602 This mechanism can be used to include BDB into other event
603 mechanisms, such as Coro::BDB.
604
605 To allow other, callback-based, events to be executed while
606 callback-less ones are run, you could use this sync prepare
607 function:
524 608
525 sub { 609 sub {
526 my $status; 610 my $status;
527 ( 611 (
528 sub { $status = $! }, 612 sub { $status = $! },
529 sub { BDB::poll while !defined $status; $! = $status }, 613 sub { BDB::poll while !defined $status; $! = $status },
530 ) 614 )
531 } 615 }
532 616
617 It works by polling for results till the request has finished and
618 then sets $! to the return value. This means that if you don't use a
619 callback, BDB would simply fall back to synchronous operations.
620
621 By default, or if the sync prepare function is set to "undef", is to
622 execute callback-less BDB requests in the foreground thread, setting
623 $! to the return value, without polling for other events.
624
533 STATISTICAL INFORMATION 625 STATISTICAL INFORMATION
534 BDB::nreqs 626 BDB::nreqs
535 Returns the number of requests currently in the ready, execute or 627 Returns the number of requests currently in the ready, execute or
536 pending states (i.e. for which their callback has not been invoked 628 pending states (i.e. for which their callback has not been invoked
537 yet). 629 yet).
538 630
… …
547 639
548 BDB::npending 640 BDB::npending
549 Returns the number of requests currently in the pending state 641 Returns the number of requests currently in the pending state
550 (executed, but not yet processed by poll_cb). 642 (executed, but not yet processed by poll_cb).
551 643
644COMMON PITFALLS
645 Unexpected Crashes
646 Remember that, by default, BDB will execute requests in parallel, in
647 somewhat random order. That means that it is easy to run a "db_get"
648 request on thesa me database as a concurrent "db_close" request, leading
649 to a crash, silent data corruption, eventually the next world war on
650 terrorism.
651
652 If you only ever use foreground requests (without a callback), this will
653 not be an issue.
654
655 Unexpected Freezes or Deadlocks
656 Remember that, by default, BDB will execute requests in parallel, which
657 easily leads to deadlocks (even concurrent put's on the same database
658 can deadlock).
659
660 You either need to run deadlock detection (and handle the resulting
661 errors), or make sure only one process ever updates the database, ine
662 one thread, e.g. by using only foreground requests (without a callback).
663
552 FORK BEHAVIOUR 664FORK BEHAVIOUR
553 This module should do "the right thing" when the process using it forks: 665 This module should do "the right thing" when the process using it forks:
554 666
555 Before the fork, BDB enters a quiescent state where no requests can be 667 Before the fork, BDB enters a quiescent state where no requests can be
556 added in other threads and no results will be processed. After the fork 668 added in other threads and no results will be processed. After the fork
557 the parent simply leaves the quiescent state and continues 669 the parent simply leaves the quiescent state and continues
… …
566 678
567 Win32 note: there is no fork on win32, and perls emulation of it is too 679 Win32 note: there is no fork on win32, and perls emulation of it is too
568 broken to be supported, so do not use BDB in a windows pseudo-fork, 680 broken to be supported, so do not use BDB in a windows pseudo-fork,
569 better yet, switch to a more capable platform. 681 better yet, switch to a more capable platform.
570 682
571 MEMORY USAGE 683MEMORY USAGE
572 Per-request usage: 684 Per-request usage:
573 685
574 Each aio request uses - depending on your architecture - around 100-200 686 Each aio request uses - depending on your architecture - around 100-200
575 bytes of memory. In addition, stat requests need a stat buffer (possibly 687 bytes of memory. In addition, stat requests need a stat buffer (possibly
576 a few hundred bytes), readdir requires a result buffer and so on. Perl 688 a few hundred bytes), readdir requires a result buffer and so on. Perl
… …
584 696
585 In the execution phase, some aio requests require more memory for 697 In the execution phase, some aio requests require more memory for
586 temporary buffers, and each thread requires a stack and other data 698 temporary buffers, and each thread requires a stack and other data
587 structures (usually around 16k-128k, depending on the OS). 699 structures (usually around 16k-128k, depending on the OS).
588 700
701WIN32 FILENAMES/DATABASE NAME MESS
702 Perl on Win32 supports only ASCII filenames (the reason is that it
703 abuses an internal flag to store wether a filename is Unicode or ANSI,
704 but that flag is used for somethign else in the perl core, so there is
705 no way to detect wether a filename is ANSI or Unicode-encoded). The BDB
706 module tries to work around this issue by assuming that the filename is
707 an ANSI filename and BDB was built for unicode support.
708
589KNOWN BUGS 709KNOWN BUGS
590 Known bugs will be fixed in the next release, except: 710 Known bugs will be fixed in the next release, except:
591 711
592 If you use a transaction in any request, and the request returns 712 If you use a transaction in any request, and the request returns
593 with an operating system error or DB_LOCK_NOTGRANTED, the internal 713 with an operating system error or DB_LOCK_NOTGRANTED, the internal
594 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, 714 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
595 above. 715 above.
596 716
597SEE ALSO 717SEE ALSO
598 Coro::BDB, IO::AIO. 718 AnyEvent::BDB (event loop integration), Coro::BDB (more natural syntax),
719 IO::AIO (nice to have).
599 720
600AUTHOR 721AUTHOR
601 Marc Lehmann <schmorp@schmorp.de> 722 Marc Lehmann <schmorp@schmorp.de>
602 http://home.schmorp.de/ 723 http://home.schmorp.de/
603 724

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