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Comparing BDB/BDB.pm (file contents):
Revision 1.18 by root, Tue Dec 4 11:07:39 2007 UTC vs.
Revision 1.53 by root, Tue Oct 21 02:21:25 2008 UTC

… …
3BDB - Asynchronous Berkeley DB access 3BDB - Asynchronous Berkeley DB access
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use BDB; 7 use BDB;
8
9 my $env = db_env_create;
10
11 mkdir "bdtest", 0700;
12 db_env_open
13 $env,
14 "bdtest",
15 BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL
16 | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE,
17 0600;
18
19 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
20
21 my $db = db_create $env;
22 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE
23 | BDB::READ_UNCOMMITTED, 0600;
24 db_put $db, undef, "key", "data", 0, sub {
25 db_del $db, undef, "key";
26 };
27 db_sync $db;
28
29 # when you also use Coro, management is easy:
30 use Coro::BDB;
31
32 # automatic event loop intergration with AnyEvent:
33 use AnyEvent::BDB;
34
35 # automatic result processing with EV:
36 my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
37
38 # with Glib:
39 add_watch Glib::IO BDB::poll_fileno,
40 in => sub { BDB::poll_cb; 1 };
41
42 # or simply flush manually
43 BDB::flush;
44
8 45
9=head1 DESCRIPTION 46=head1 DESCRIPTION
10 47
11See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). 48See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
12The BDB API is very similar to the C API (the translation has been very faithful). 49The BDB API is very similar to the C API (the translation has been very faithful).
… …
71no warnings; 108no warnings;
72use strict 'vars'; 109use strict 'vars';
73 110
74use base 'Exporter'; 111use base 'Exporter';
75 112
113our $VERSION;
114
76BEGIN { 115BEGIN {
77 our $VERSION = '1.2'; 116 $VERSION = '1.81';
78 117
79 our @BDB_REQ = qw( 118 our @BDB_REQ = qw(
80 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect 119 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
81 db_env_memp_sync db_env_memp_trickle 120 db_env_memp_sync db_env_memp_trickle db_env_dbrename db_env_dbremove
82 db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range 121 db_env_log_archive
122 db_open db_close db_compact db_sync db_upgrade
123 db_put db_exists db_get db_pget db_del db_key_range
83 db_txn_commit db_txn_abort db_txn_finish 124 db_txn_commit db_txn_abort db_txn_finish
84 db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del 125 db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
85 db_sequence_open db_sequence_close 126 db_sequence_open db_sequence_close
86 db_sequence_get db_sequence_remove 127 db_sequence_get db_sequence_remove
87 ); 128 );
… …
95 136
96 require XSLoader; 137 require XSLoader;
97 XSLoader::load ("BDB", $VERSION); 138 XSLoader::load ("BDB", $VERSION);
98} 139}
99 140
100=head2 BERKELEYDB FUNCTIONS 141=head1 BERKELEYDB FUNCTIONS
101 142
102All of these are functions. The create functions simply return a new 143All of these are functions. The create functions simply return a new
103object and never block. All the remaining functions all take an optional 144object and never block. All the remaining functions take an optional
104callback as last argument. If it is missing, then the fucntion will be 145callback as last argument. If it is missing, then the function will be
105executed synchronously. 146executed synchronously. In both cases, C<$!> will reflect the return value
147of the function.
106 148
107BDB functions that cannot block (mostly functions that manipulate 149BDB functions that cannot block (mostly functions that manipulate
108settings) are method calls on the relevant objects, so the rule of thumb 150settings) are method calls on the relevant objects, so the rule of thumb
109is: if its a method, its not blocking, if its a function, it takes a 151is: if it's a method, it's not blocking, if it's a function, it takes a
110callback as last argument. 152callback as last argument.
111 153
112In the following, C<$int> signifies an integer return value, 154In the following, C<$int> signifies an integer return value,
113C<octetstring> is a "binary string" (i.e. a perl string with no character 155C<bdb_filename> is a "filename" (octets on unix, madness on windows),
114indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some 156C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
115integer, C<NV> is a floating point value. 157floating point value.
116 158
117The C<SV *> types are generic perl scalars (for input and output of data 159Most C<SV *> types are generic perl scalars (for input and output of data
118values), and the C<SV *callback> is the optional callback function to call 160values).
119when the request is completed.
120 161
121The various C<DB_ENV> etc. arguments are handles return by 162The various C<DB_ENV> etc. arguments are handles return by
122C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an 163C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
123appended C<_ornull> this means they are optional and you can pass C<undef> 164appended C<_ornull> this means they are optional and you can pass C<undef>
124for them, resulting a NULL pointer on the C level. 165for them, resulting a NULL pointer on the C level.
125 166
167The C<SV *callback> is the optional callback function to call when the
168request is completed. This last callback argument is special: the callback
169is simply the last argument passed. If there are "optional" arguments
170before the callback they can be left out. The callback itself can be left
171out or specified as C<undef>, in which case the function will be executed
172synchronously.
173
174For example, C<db_env_txn_checkpoint> usually is called with all integer
175arguments zero. These can be left out, so all of these specify a call
176to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
177callback to be called:
178
179 db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
180 db_env_txn_checkpoint $db_env, 0, 0, sub { };
181 db_env_txn_checkpoint $db_env, sub { };
182
183While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
184executed synchronously:
185
186 db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
187 db_env_txn_checkpoint $db_env, 0, 0, 0;
188 db_env_txn_checkpoint $db_env, 0;
189
126=head3 BDB functions 190=head2 BDB functions
127 191
128Functions in the BDB namespace, exported by default: 192Functions in the BDB namespace, exported by default:
129 193
130 $env = db_env_create (U32 env_flags = 0) 194 $env = db_env_create (U32 env_flags = 0)
131 flags: RPCCLIENT 195 flags: RPCCLIENT
132 196
133 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 197 db_env_open (DB_ENV *env, bdb_filename db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef)
134 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 198 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
135 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) 199 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef)
136 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 200 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
137 flags: FORCE 201 flags: FORCE
138 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) 202 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef)
139 atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST 203 atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
140 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) 204 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef)
141 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) 205 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef)
206 db_env_dbremove (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
207 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)
208 db_env_log_archive (DB_ENV *env, SV *listp, U32 flags = 0, SV *callback = &PL_sv_undef)
142 209
143 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 210 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
144 flags: XA_CREATE 211 flags: XA_CREATE
145 212
146 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 213 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)
147 flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE 214 flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
148 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 215 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
149 flags: DB_NOSYNC 216 flags: DB_NOSYNC
217 db_upgrade (DB *db, bdb_filename file, U32 flags = 0, SV *callback = &PL_sv_undef)
150 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) 218 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)
151 flags: FREELIST_ONLY FREE_SPACE 219 flags: FREELIST_ONLY FREE_SPACE
152 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 220 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
153 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) 221 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
154 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 222 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
155 flags: APPEND NODUPDATA NOOVERWRITE 223 flags: APPEND NODUPDATA NOOVERWRITE
224 db_exists (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = 0) (v4.6)
156 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 225 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
157 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW 226 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
158 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 227 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
159 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW 228 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
160 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 229 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef)
… …
177 db_sequence_get (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, int delta, SV *seq_value, U32 flags = DB_TXN_NOSYNC, SV *callback = &PL_sv_undef) 246 db_sequence_get (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, int delta, SV *seq_value, U32 flags = DB_TXN_NOSYNC, SV *callback = &PL_sv_undef)
178 flags: TXN_NOSYNC 247 flags: TXN_NOSYNC
179 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 248 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
180 flags: TXN_NOSYNC 249 flags: TXN_NOSYNC
181 250
182=head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) 251=head3 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
183 252
184This is not actually a Berkeley DB function but a BDB module 253This is not actually a Berkeley DB function but a BDB module
185extension. The background for this exytension is: It is very annoying to 254extension. The background for this exytension is: It is very annoying to
186have to check every single BDB function for error returns and provide a 255have to check every single BDB function for error returns and provide a
187codepath out of your transaction. While the BDB module still makes this 256codepath out of your transaction. While the BDB module still makes this
… …
213 282
214You can use the C<< $txn->failed >> method to check wether a transaction 283You can use the C<< $txn->failed >> method to check wether a transaction
215has failed in this way and abort further processing (excluding 284has failed in this way and abort further processing (excluding
216C<db_txn_finish>). 285C<db_txn_finish>).
217 286
218=head3 DB_ENV/database environment methods 287=head2 DB_ENV/database environment methods
219 288
220Methods available on DB_ENV/$env handles: 289Methods available on DB_ENV/$env handles:
221 290
222 DESTROY (DB_ENV_ornull *env) 291 DESTROY (DB_ENV_ornull *env)
223 CODE: 292 CODE:
… …
227 $int = $env->set_data_dir (const char *dir) 296 $int = $env->set_data_dir (const char *dir)
228 $int = $env->set_tmp_dir (const char *dir) 297 $int = $env->set_tmp_dir (const char *dir)
229 $int = $env->set_lg_dir (const char *dir) 298 $int = $env->set_lg_dir (const char *dir)
230 $int = $env->set_shm_key (long shm_key) 299 $int = $env->set_shm_key (long shm_key)
231 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 300 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
232 $int = $env->set_flags (U32 flags, int onoff) 301 $int = $env->set_flags (U32 flags, int onoff = 1)
302 $int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
303 $int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
233 $env->set_errfile (FILE *errfile = 0) 304 $env->set_errfile (FILE *errfile = 0)
234 $env->set_msgfile (FILE *msgfile = 0) 305 $env->set_msgfile (FILE *msgfile = 0)
235 $int = $env->set_verbose (U32 which, int onoff = 1) 306 $int = $env->set_verbose (U32 which, int onoff = 1)
236 $int = $env->set_encrypt (const char *password, U32 flags = 0) 307 $int = $env->set_encrypt (const char *password, U32 flags = 0)
237 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) 308 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
… …
242 $int = $env->set_lk_max_lockers (U32 max) 313 $int = $env->set_lk_max_lockers (U32 max)
243 $int = $env->set_lk_max_locks (U32 max) 314 $int = $env->set_lk_max_locks (U32 max)
244 $int = $env->set_lk_max_objects (U32 max) 315 $int = $env->set_lk_max_objects (U32 max)
245 $int = $env->set_lg_bsize (U32 max) 316 $int = $env->set_lg_bsize (U32 max)
246 $int = $env->set_lg_max (U32 max) 317 $int = $env->set_lg_max (U32 max)
318 $int = $env->mutex_set_increment (U32 increment)
319 $int = $env->mutex_set_tas_spins (U32 tas_spins)
320 $int = $env->mutex_set_max (U32 max)
321 $int = $env->mutex_set_align (U32 align)
247 322
248 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 323 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
249 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC 324 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
325 $txn = $env->cdsgroup_begin; (v4.5)
250 326
251=head4 Example: 327=head3 Example:
252 328
253 use AnyEvent; 329 use AnyEvent;
254 use BDB; 330 use BDB;
255 331
256 our $FH; open $FH, "<&=" . BDB::poll_fileno; 332 our $FH; open $FH, "<&=" . BDB::poll_fileno;
… …
268 0600; 344 0600;
269 345
270 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 346 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
271 347
272 348
273=head3 DB/database methods 349=head2 DB/database methods
274 350
275Methods available on DB/$db handles: 351Methods available on DB/$db handles:
276 352
277 DESTROY (DB_ornull *db) 353 DESTROY (DB_ornull *db)
278 CODE: 354 CODE:
… …
304 380
305 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 381 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
306 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT 382 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
307 $seq = $db->sequence (U32 flags = 0) 383 $seq = $db->sequence (U32 flags = 0)
308 384
309=head4 Example: 385=head3 Example:
310 386
311 my $db = db_create $env; 387 my $db = db_create $env;
312 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600; 388 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600;
313 389
314 for (1..1000) { 390 for (1..1000) {
… …
321 db_del $db, undef, "key $_" for 1..1000; 397 db_del $db, undef, "key $_" for 1..1000;
322 398
323 db_sync $db; 399 db_sync $db;
324 400
325 401
326=head3 DB_TXN/transaction methods 402=head2 DB_TXN/transaction methods
327 403
328Methods available on DB_TXN/$txn handles: 404Methods available on DB_TXN/$txn handles:
329 405
330 DESTROY (DB_TXN_ornull *txn) 406 DESTROY (DB_TXN_ornull *txn)
331 CODE: 407 CODE:
… …
337 413
338 $bool = $txn->failed 414 $bool = $txn->failed
339 # see db_txn_finish documentation, above 415 # see db_txn_finish documentation, above
340 416
341 417
342=head3 DBC/cursor methods 418=head2 DBC/cursor methods
343 419
344Methods available on DBC/$dbc handles: 420Methods available on DBC/$dbc handles:
345 421
346 DESTROY (DBC_ornull *dbc) 422 DESTROY (DBC_ornull *dbc)
347 CODE: 423 CODE:
348 if (dbc) 424 if (dbc)
349 dbc->c_close (dbc); 425 dbc->c_close (dbc);
350 426
427 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
428
351=head4 Example: 429=head3 Example:
352 430
353 my $c = $db->cursor; 431 my $c = $db->cursor;
354 432
355 for (;;) { 433 for (;;) {
356 db_c_get $c, my $key, my $data, BDB::NEXT; 434 db_c_get $c, my $key, my $data, BDB::NEXT;
… …
359 } 437 }
360 438
361 db_c_close $c; 439 db_c_close $c;
362 440
363 441
364=head3 DB_SEQUENCE/sequence methods 442=head2 DB_SEQUENCE/sequence methods
365 443
366Methods available on DB_SEQUENCE/$seq handles: 444Methods available on DB_SEQUENCE/$seq handles:
367 445
368 DESTROY (DB_SEQUENCE_ornull *seq) 446 DESTROY (DB_SEQUENCE_ornull *seq)
369 CODE: 447 CODE:
… …
374 $int = $seq->set_cachesize (U32 size) 452 $int = $seq->set_cachesize (U32 size)
375 $int = $seq->set_flags (U32 flags) 453 $int = $seq->set_flags (U32 flags)
376 flags: SEQ_DEC SEQ_INC SEQ_WRAP 454 flags: SEQ_DEC SEQ_INC SEQ_WRAP
377 $int = $seq->set_range (db_seq_t min, db_seq_t max) 455 $int = $seq->set_range (db_seq_t min, db_seq_t max)
378 456
379=head4 Example: 457=head3 Example:
380 458
381 my $seq = $db->sequence; 459 my $seq = $db->sequence;
382 460
383 db_sequence_open $seq, undef, "seq", BDB::CREATE; 461 db_sequence_open $seq, undef, "seq", BDB::CREATE;
384 db_sequence_get $seq, undef, 1, my $value; 462 db_sequence_get $seq, undef, 1, my $value;
385 463
386 464
387=head2 SUPPORT FUNCTIONS 465=head1 SUPPORT FUNCTIONS
388 466
389=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 467=head2 EVENT PROCESSING AND EVENT LOOP INTEGRATION
390 468
391=over 4 469=over 4
470
471=item $msg = BDB::strerror [$errno]
472
473Returns the string corresponding to the given errno value. If no argument
474is given, use C<$!>.
475
476Note that the BDB module also patches the C<$!> variable directly, so you
477should be able to get a bdb error string by simply stringifying C<$!>.
392 478
393=item $fileno = BDB::poll_fileno 479=item $fileno = BDB::poll_fileno
394 480
395Return the I<request result pipe file descriptor>. This filehandle must be 481Return the I<request result pipe file descriptor>. This filehandle must be
396polled for reading by some mechanism outside this module (e.g. Event or 482polled for reading by some mechanism outside this module (e.g. Event or
… …
473 BDB::poll_wait, BDB::poll_cb 559 BDB::poll_wait, BDB::poll_cb
474 while BDB::nreqs; 560 while BDB::nreqs;
475 561
476=back 562=back
477 563
564=head2 VERSION CHECKING
565
566BerkeleyDB comes in various versions, many of them have minor
567incompatibilities. This means that traditional "at least version x.x"
568checks are often not sufficient.
569
570Example: set the log_autoremove option in a way compatible with <v4.7 and
571v4.7. Note the use of & on the constants to avoid triggering a compiletime
572bug when the symbol isn't available.
573
574 $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
575 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
576
577=over 4
578
579=item BDB::VERSION
580
581The C<BDB::VERSION> function, when called without arguments, returns the
582Berkeley DB version as a v-string (usually with 3 components). You should
583use C<lt> and C<ge> operators exclusively to make comparisons.
584
585Example: check for at least version 4.7.
586
587 BDB::VERSION ge v4.7 or die;
588
589=item BDB::VERSION min-version
590
591Returns true if the BDB version is at least the given version (specified
592as a v-string), false otherwise.
593
594Example: check for at least version 4.5.
595
596 BDB::VERSION v4.7 or die;
597
598=item BDB::VERSION min-version, max-version
599
600Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
601and less then C<max-version>.
602
603Example: check wether version is strictly less then v4.7.
604
605 BDB::VERSION v0, v4.7
606 or die "version 4.7 is not yet supported";
607
608=back
609
610=cut
611
612sub VERSION {
613 # I was dumb enough to override the VERSION method here, so let's try
614 # to fix it up.
615
616 if ($_[0] eq __PACKAGE__) {
617 $VERSION
618 } else {
619 if (@_ > 0) {
620 return undef if VERSION_v lt $_[0];
621 if (@_ > 1) {
622 return undef if VERSION_v ge $_[1];
623 }
624 }
625
626 VERSION_v
627 }
628}
629
478=head3 CONTROLLING THE NUMBER OF THREADS 630=head2 CONTROLLING THE NUMBER OF THREADS
479 631
480=over 4 632=over 4
481 633
482=item BDB::min_parallel $nthreads 634=item BDB::min_parallel $nthreads
483 635
… …
544 696
545You can still queue as many requests as you want. Therefore, 697You can still queue as many requests as you want. Therefore,
546C<max_oustsanding> is mainly useful in simple scripts (with low values) or 698C<max_oustsanding> is mainly useful in simple scripts (with low values) or
547as a stop gap to shield against fatal memory overflow (with large values). 699as a stop gap to shield against fatal memory overflow (with large values).
548 700
549=item BDB::set_sync_prepare $cb 701=item $old_cb = BDB::set_sync_prepare $cb
550 702
551Sets a callback that is called whenever a request is created without an 703Sets a callback that is called whenever a request is created without an
552explicit callback. It has to return two code references. The first is used 704explicit callback. It has to return two code references. The first is used
553as the request callback, and the second is called to wait until the first 705as the request callback (it should save the return status), and the second
554callback has been called. The default implementation works like this: 706is called to wait until the first callback has been called (it must set
707C<$!> to the return status).
708
709This mechanism can be used to include BDB into other event mechanisms,
710such as L<Coro::BDB>.
711
712To allow other, callback-based, events to be executed while callback-less
713ones are run, you could use this sync prepare function:
555 714
556 sub { 715 sub {
557 my $status; 716 my $status;
558 ( 717 (
559 sub { $status = $! }, 718 sub { $status = $! },
560 sub { BDB::poll while !defined $status; $! = $status }, 719 sub { BDB::poll while !defined $status; $! = $status },
561 ) 720 )
562 } 721 }
563 722
723It works by polling for results till the request has finished and then
724sets C<$!> to the return value. This means that if you don't use a
725callback, BDB would simply fall back to synchronous operations.
726
727By default, or if the sync prepare function is set to C<undef>, is to
728execute callback-less BDB requests in the foreground thread, setting C<$!>
729to the return value, without polling for other events.
730
564=back 731=back
565 732
566=head3 STATISTICAL INFORMATION 733=head2 STATISTICAL INFORMATION
567 734
568=over 4 735=over 4
569 736
570=item BDB::nreqs 737=item BDB::nreqs
571 738
… …
589 756
590=back 757=back
591 758
592=cut 759=cut
593 760
594set_sync_prepare { 761set_sync_prepare (undef);
595 my $status;
596 (
597 sub {
598 $status = $!;
599 },
600 sub {
601 BDB::poll while !defined $status;
602 $! = $status;
603 },
604 )
605};
606 762
607min_parallel 8; 763min_parallel 8;
608 764
609END { flush } 765END { flush }
610 766
6111; 7671;
612 768
769=head1 COMMON PITFALLS
770
771=head2 Unexpected Crashes
772
773Remember that, by default, BDB will execute requests in parallel, in
774somewhat random order. That means that it is easy to run a C<db_get>
775request on thesa me database as a concurrent C<db_close> request, leading
776to a crash, silent data corruption, eventually the next world war on
777terrorism.
778
779If you only ever use foreground requests (without a callback), this will
780not be an issue.
781
782=head2 Unexpected Freezes or Deadlocks
783
784Remember that, by default, BDB will execute requests in parallel, which
785easily leads to deadlocks (even concurrent put's on the same database can
786deadlock).
787
788You either need to run deadlock detection (and handle the resulting
789errors), or make sure only one process ever updates the database, ine one
790thread, e.g. by using only foreground requests (without a callback).
791
613=head2 FORK BEHAVIOUR 792=head1 FORK BEHAVIOUR
614 793
615This module should do "the right thing" when the process using it forks: 794This module should do "the right thing" when the process using it forks:
616 795
617Before the fork, BDB enters a quiescent state where no requests 796Before the fork, BDB enters a quiescent state where no requests
618can be added in other threads and no results will be processed. After 797can be added in other threads and no results will be processed. After
… …
624 803
625In short: the parent will, after a short pause, continue as if fork had 804In short: the parent will, after a short pause, continue as if fork had
626not been called, while the child will act as if BDB has not been used 805not been called, while the child will act as if BDB has not been used
627yet. 806yet.
628 807
808Win32 note: there is no fork on win32, and perls emulation of it is too
809broken to be supported, so do not use BDB in a windows pseudo-fork, better
810yet, switch to a more capable platform.
811
629=head2 MEMORY USAGE 812=head1 MEMORY USAGE
630 813
631Per-request usage: 814Per-request usage:
632 815
633Each aio request uses - depending on your architecture - around 100-200 816Each aio request uses - depending on your architecture - around 100-200
634bytes of memory. In addition, stat requests need a stat buffer (possibly 817bytes of memory. In addition, stat requests need a stat buffer (possibly
… …
643 826
644In the execution phase, some aio requests require more memory for 827In the execution phase, some aio requests require more memory for
645temporary buffers, and each thread requires a stack and other data 828temporary buffers, and each thread requires a stack and other data
646structures (usually around 16k-128k, depending on the OS). 829structures (usually around 16k-128k, depending on the OS).
647 830
831=head1 WIN32 FILENAMES/DATABASE NAME MESS
832
833Perl on Win32 supports only ASCII filenames (the reason is that it abuses
834an internal flag to store wether a filename is Unicode or ANSI, but that
835flag is used for somethign else in the perl core, so there is no way to
836detect wether a filename is ANSI or Unicode-encoded). The BDB module
837tries to work around this issue by assuming that the filename is an ANSI
838filename and BDB was built for unicode support.
839
648=head1 KNOWN BUGS 840=head1 KNOWN BUGS
649 841
650Known bugs will be fixed in the next release, except: 842Known bugs will be fixed in the next release, except:
651 843
652 If you use a transaction in any request, and the request returns 844 If you use a transaction in any request, and the request returns
… …
654 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, 846 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
655 above. 847 above.
656 848
657=head1 SEE ALSO 849=head1 SEE ALSO
658 850
659L<Coro::BDB>, L<IO::AIO>. 851L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
852syntax), L<IO::AIO> (nice to have).
660 853
661=head1 AUTHOR 854=head1 AUTHOR
662 855
663 Marc Lehmann <schmorp@schmorp.de> 856 Marc Lehmann <schmorp@schmorp.de>
664 http://home.schmorp.de/ 857 http://home.schmorp.de/

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