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Comparing BDB/BDB.pm (file contents):
Revision 1.10 by root, Mon Aug 13 12:01:45 2007 UTC vs.
Revision 1.18 by root, Tue Dec 4 11:07:39 2007 UTC

… …
7 use BDB; 7 use BDB;
8 8
9=head1 DESCRIPTION 9=head1 DESCRIPTION
10 10
11See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). 11See 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 ahs been very faithful). 12The BDB API is very similar to the C API (the translation has been very faithful).
13 13
14See also the example sections in the document below and possibly the eg/ 14See also the example sections in the document below and possibly the eg/
15subdirectory of the BDB distribution. Last not least see the IO::AIO 15subdirectory of the BDB distribution. Last not least see the IO::AIO
16documentation, as that module uses almost the same asynchronous request 16documentation, as that module uses almost the same asynchronous request
17model as this module. 17model as this module.
… …
72use strict 'vars'; 72use strict 'vars';
73 73
74use base 'Exporter'; 74use base 'Exporter';
75 75
76BEGIN { 76BEGIN {
77 our $VERSION = '0.6'; 77 our $VERSION = '1.2';
78 78
79 our @BDB_REQ = qw( 79 our @BDB_REQ = qw(
80 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect 80 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
81 db_env_memp_sync db_env_memp_trickle 81 db_env_memp_sync db_env_memp_trickle
82 db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range 82 db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range
83 db_txn_commit db_txn_abort 83 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 84 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 85 db_sequence_open db_sequence_close
86 db_sequence_get db_sequence_remove 86 db_sequence_get db_sequence_remove
87 ); 87 );
88 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create)); 88 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
… …
116 116
117The C<SV *> types are generic perl scalars (for input and output of data 117The 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 118values), and the C<SV *callback> is the optional callback function to call
119when the request is completed. 119when the request is completed.
120 120
121The various C<DB_ENV> etc. arguments are handles return by db_env_create>, 121The various C<DB_ENV> etc. arguments are handles return by
122C<C<db_create>, C<txn_begin> and so on. If they have an appended _ornull> 122C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
123C<this means they are optional and you can pass C<undef> for them, 123appended C<_ornull> this means they are optional and you can pass C<undef>
124C<resulting a NULL pointer on the C level. 124for them, resulting a NULL pointer on the C level.
125 125
126=head3 BDB functions 126=head3 BDB functions
127 127
128Functions in the BDB namespace, exported by default: 128Functions in the BDB namespace, exported by default:
129 129
130 $env = db_env_create (U32 env_flags = 0) 130 $env = db_env_create (U32 env_flags = 0)
131 flags: RPCCLIENT
131 132
132 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 133 db_env_open (DB_ENV *env, octetstring 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
133 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) 135 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef)
134 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, 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)
137 flags: FORCE
135 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) 138 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
136 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) 140 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef)
137 db_env_memp_trickle (DB_ENV *env, int percent, 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)
138 142
139 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 143 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
144 flags: XA_CREATE
140 145
141 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 146 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring 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
142 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 148 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
149 flags: DB_NOSYNC
143 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_unde 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)
151 flags: FREELIST_ONLY FREE_SPACE
144 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 152 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
145 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, 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)
146 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, 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)
155 flags: APPEND NODUPDATA NOOVERWRITE
147 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 156 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
148 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 158 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
149 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 160 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef)
150 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) 161 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
162 flags: TXN_NOSYNC TXN_SYNC
151 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 163 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef)
164
152 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 165 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef)
153 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) 166 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef)
154 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 167 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
168 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
155 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 169 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
170 flags: CURRENT FIRST GET_BOTH GET_BOTH_RANGE GET_RECNO JOIN_ITEM LAST NEXT NEXT_DUP NEXT_NODUP PREV PREV_DUP PREV_NODUP SET SET_RANGE SET_RECNO READ_UNCOMMITTED MULTIPLE MULTIPLE_KEY RMW
156 db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 171 db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
157 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef) 172 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef)
158 173
159 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 174 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef)
175 flags: CREATE EXCL
160 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 176 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef)
161 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) 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)
178 flags: TXN_NOSYNC
162 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 179 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
180 flags: TXN_NOSYNC
163 181
182=head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
183
184This is not actually a Berkeley DB function but a BDB module
185extension. The background for this exytension is: It is very annoying to
186have to check every single BDB function for error returns and provide a
187codepath out of your transaction. While the BDB module still makes this
188possible, it contains the following extensions:
189
190When a transaction-protected function returns any operating system
191error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
192transaction. This flag is also set by Berkeley DB functions themselves
193when an operation fails with LOCK_DEADLOCK, and it causes all further
194operations on that transaction (including C<db_txn_commit>) to fail.
195
196The C<db_txn_finish> request will look at this flag, and, if it is set,
197will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
198if it isn't set to something else yet). If it isn't set, it will call
199C<db_txn_commit> and return the error normally.
200
201How to use this? Easy: just write your transaction normally:
202
203 my $txn = $db_env->txn_begin;
204 db_get $db, $txn, "key", my $data;
205 db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
206 db_txn_finish $txn;
207 die "transaction failed" if $!;
208
209That is, handle only the expected errors. If something unexpected happens
210(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
211requests (db_put in this case) will simply be skipped (they will fail with
212LOCK_DEADLOCK) and the transaction will be aborted.
213
214You can use the C<< $txn->failed >> method to check wether a transaction
215has failed in this way and abort further processing (excluding
216C<db_txn_finish>).
164 217
165=head3 DB_ENV/database environment methods 218=head3 DB_ENV/database environment methods
166 219
167Methods available on DB_ENV/$env handles: 220Methods available on DB_ENV/$env handles:
168 221
… …
179 $int = $env->set_flags (U32 flags, int onoff) 232 $int = $env->set_flags (U32 flags, int onoff)
180 $env->set_errfile (FILE *errfile = 0) 233 $env->set_errfile (FILE *errfile = 0)
181 $env->set_msgfile (FILE *msgfile = 0) 234 $env->set_msgfile (FILE *msgfile = 0)
182 $int = $env->set_verbose (U32 which, int onoff = 1) 235 $int = $env->set_verbose (U32 which, int onoff = 1)
183 $int = $env->set_encrypt (const char *password, U32 flags = 0) 236 $int = $env->set_encrypt (const char *password, U32 flags = 0)
184 $int = $env->set_timeout (NV timeout, U32 flags) 237 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
185 $int = $env->set_mp_max_openfd (int maxopenfd); 238 $int = $env->set_mp_max_openfd (int maxopenfd);
186 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); 239 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
187 $int = $env->set_mp_mmapsize (int mmapsize_mb) 240 $int = $env->set_mp_mmapsize (int mmapsize_mb)
188 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) 241 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
189 $int = $env->set_lk_max_lockers (U32 max) 242 $int = $env->set_lk_max_lockers (U32 max)
… …
191 $int = $env->set_lk_max_objects (U32 max) 244 $int = $env->set_lk_max_objects (U32 max)
192 $int = $env->set_lg_bsize (U32 max) 245 $int = $env->set_lg_bsize (U32 max)
193 $int = $env->set_lg_max (U32 max) 246 $int = $env->set_lg_max (U32 max)
194 247
195 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 248 $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
196 250
197=head4 example 251=head4 Example:
198 252
199 use AnyEvent; 253 use AnyEvent;
200 use BDB; 254 use BDB;
201 255
202 our $FH; open $FH, "<&=" . BDB::poll_fileno; 256 our $FH; open $FH, "<&=" . BDB::poll_fileno;
… …
229 SvREFCNT_dec (env); 283 SvREFCNT_dec (env);
230 } 284 }
231 285
232 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 286 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
233 $int = $db->set_flags (U32 flags) 287 $int = $db->set_flags (U32 flags)
288 flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
289 Btree: DUP DUPSORT RECNUM REVSPLITOFF
290 Hash: DUP DUPSORT
291 Queue: INORDER
292 Recno: RENUMBER SNAPSHOT
293
234 $int = $db->set_encrypt (const char *password, U32 flags) 294 $int = $db->set_encrypt (const char *password, U32 flags)
235 $int = $db->set_lorder (int lorder) 295 $int = $db->set_lorder (int lorder)
236 $int = $db->set_bt_minkey (U32 minkey) 296 $int = $db->set_bt_minkey (U32 minkey)
237 $int = $db->set_re_delim (int delim) 297 $int = $db->set_re_delim (int delim)
238 $int = $db->set_re_pad (int re_pad) 298 $int = $db->set_re_pad (int re_pad)
… …
241 $int = $db->set_h_ffactor (U32 h_ffactor) 301 $int = $db->set_h_ffactor (U32 h_ffactor)
242 $int = $db->set_h_nelem (U32 h_nelem) 302 $int = $db->set_h_nelem (U32 h_nelem)
243 $int = $db->set_q_extentsize (U32 extentsize) 303 $int = $db->set_q_extentsize (U32 extentsize)
244 304
245 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 305 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
306 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
246 $seq = $db->sequence (U32 flags = 0) 307 $seq = $db->sequence (U32 flags = 0)
247 308
248=head4 example 309=head4 Example:
249 310
250 my $db = db_create $env; 311 my $db = db_create $env;
251 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600; 312 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600;
252 313
253 for (1..1000) { 314 for (1..1000) {
… …
269 DESTROY (DB_TXN_ornull *txn) 330 DESTROY (DB_TXN_ornull *txn)
270 CODE: 331 CODE:
271 if (txn) 332 if (txn)
272 txn->abort (txn); 333 txn->abort (txn);
273 334
274 $int = $txn->set_timeout (NV timeout, U32 flags) 335 $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
336 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
337
338 $bool = $txn->failed
339 # see db_txn_finish documentation, above
275 340
276 341
277=head3 DBC/cursor methods 342=head3 DBC/cursor methods
278 343
279Methods available on DBC/$dbc handles: 344Methods available on DBC/$dbc handles:
… …
281 DESTROY (DBC_ornull *dbc) 346 DESTROY (DBC_ornull *dbc)
282 CODE: 347 CODE:
283 if (dbc) 348 if (dbc)
284 dbc->c_close (dbc); 349 dbc->c_close (dbc);
285 350
286=head4 example 351=head4 Example:
287 352
288 my $c = $db->cursor; 353 my $c = $db->cursor;
289 354
290 for (;;) { 355 for (;;) {
291 db_c_get $c, my $key, my $data, BDB::NEXT; 356 db_c_get $c, my $key, my $data, BDB::NEXT;
… …
293 last if $!; 358 last if $!;
294 } 359 }
295 360
296 db_c_close $c; 361 db_c_close $c;
297 362
363
298=head3 DB_SEQUENCE/sequence methods 364=head3 DB_SEQUENCE/sequence methods
299 365
300Methods available on DB_SEQUENCE/$seq handles: 366Methods available on DB_SEQUENCE/$seq handles:
301 367
302 DESTROY (DB_SEQUENCE_ornull *seq) 368 DESTROY (DB_SEQUENCE_ornull *seq)
… …
305 seq->close (seq, 0); 371 seq->close (seq, 0);
306 372
307 $int = $seq->initial_value (db_seq_t value) 373 $int = $seq->initial_value (db_seq_t value)
308 $int = $seq->set_cachesize (U32 size) 374 $int = $seq->set_cachesize (U32 size)
309 $int = $seq->set_flags (U32 flags) 375 $int = $seq->set_flags (U32 flags)
376 flags: SEQ_DEC SEQ_INC SEQ_WRAP
310 $int = $seq->set_range (db_seq_t min, db_seq_t max) 377 $int = $seq->set_range (db_seq_t min, db_seq_t max)
311 378
312=head4 example 379=head4 Example:
313 380
314 my $seq = $db->sequence; 381 my $seq = $db->sequence;
315 382
316 db_sequence_open $seq, undef, "seq", BDB::CREATE; 383 db_sequence_open $seq, undef, "seq", BDB::CREATE;
317 db_sequence_get $seq, undef, 1, my $value; 384 db_sequence_get $seq, undef, 1, my $value;
… …
368interactiveness when perl is not fast enough to process all requests in 435interactiveness when perl is not fast enough to process all requests in
369time. 436time.
370 437
371For interactive programs, values such as C<0.01> to C<0.1> should be fine. 438For interactive programs, values such as C<0.01> to C<0.1> should be fine.
372 439
373Example: Install an Event watcher that automatically calls 440Example: Install an EV watcher that automatically calls
374BDB::poll_cb with low priority, to ensure that other parts of the 441BDB::poll_cb with low priority, to ensure that other parts of the
375program get the CPU sometimes even under high AIO load. 442program get the CPU sometimes even under high load.
376 443
377 # try not to spend much more than 0.1s in poll_cb 444 # try not to spend much more than 0.1s in poll_cb
378 BDB::max_poll_time 0.1; 445 BDB::max_poll_time 0.1;
379 446
380 # use a low priority so other tasks have priority 447 my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
381 Event->io (fd => BDB::poll_fileno,
382 poll => 'r', nice => 1,
383 cb => &BDB::poll_cb);
384 448
385=item BDB::poll_wait 449=item BDB::poll_wait
386 450
387If there are any outstanding requests and none of them in the result 451If there are any outstanding requests and none of them in the result
388phase, wait till the result filehandle becomes ready for reading (simply 452phase, wait till the result filehandle becomes ready for reading (simply
… …
400 464
401 BDB::poll_wait, BDB::poll_cb 465 BDB::poll_wait, BDB::poll_cb
402 466
403=item BDB::flush 467=item BDB::flush
404 468
405Wait till all outstanding AIO requests have been handled. 469Wait till all outstanding BDB requests have been handled.
406 470
407Strictly equivalent to: 471Strictly equivalent to:
408 472
409 BDB::poll_wait, BDB::poll_cb 473 BDB::poll_wait, BDB::poll_cb
410 while BDB::nreqs; 474 while BDB::nreqs;
… …
415 479
416=over 4 480=over 4
417 481
418=item BDB::min_parallel $nthreads 482=item BDB::min_parallel $nthreads
419 483
420Set the minimum number of AIO threads to C<$nthreads>. The current 484Set the minimum number of BDB threads to C<$nthreads>. The current
421default is C<8>, which means eight asynchronous operations can execute 485default is C<8>, which means eight asynchronous operations can execute
422concurrently at any one time (the number of outstanding requests, 486concurrently at any one time (the number of outstanding requests,
423however, is unlimited). 487however, is unlimited).
424 488
425BDB starts threads only on demand, when an AIO request is queued and 489BDB starts threads only on demand, when an BDB request is queued and
426no free thread exists. Please note that queueing up a hundred requests can 490no free thread exists. Please note that queueing up a hundred requests can
427create demand for a hundred threads, even if it turns out that everything 491create demand for a hundred threads, even if it turns out that everything
428is in the cache and could have been processed faster by a single thread. 492is in the cache and could have been processed faster by a single thread.
429 493
430It is recommended to keep the number of threads relatively low, as some 494It is recommended to keep the number of threads relatively low, as some
… …
435Under most circumstances you don't need to call this function, as the 499Under most circumstances you don't need to call this function, as the
436module selects a default that is suitable for low to moderate load. 500module selects a default that is suitable for low to moderate load.
437 501
438=item BDB::max_parallel $nthreads 502=item BDB::max_parallel $nthreads
439 503
440Sets the maximum number of AIO threads to C<$nthreads>. If more than the 504Sets the maximum number of BDB threads to C<$nthreads>. If more than the
441specified number of threads are currently running, this function kills 505specified number of threads are currently running, this function kills
442them. This function blocks until the limit is reached. 506them. This function blocks until the limit is reached.
443 507
444While C<$nthreads> are zero, aio requests get queued but not executed 508While C<$nthreads> are zero, aio requests get queued but not executed
445until the number of threads has been increased again. 509until the number of threads has been increased again.
… …
548 612
549=head2 FORK BEHAVIOUR 613=head2 FORK BEHAVIOUR
550 614
551This module should do "the right thing" when the process using it forks: 615This module should do "the right thing" when the process using it forks:
552 616
553Before the fork, IO::AIO enters a quiescent state where no requests 617Before the fork, BDB enters a quiescent state where no requests
554can be added in other threads and no results will be processed. After 618can be added in other threads and no results will be processed. After
555the fork the parent simply leaves the quiescent state and continues 619the fork the parent simply leaves the quiescent state and continues
556request/result processing, while the child frees the request/result queue 620request/result processing, while the child frees the request/result queue
557(so that the requests started before the fork will only be handled in the 621(so that the requests started before the fork will only be handled in the
558parent). Threads will be started on demand until the limit set in the 622parent). Threads will be started on demand until the limit set in the
559parent process has been reached again. 623parent process has been reached again.
560 624
561In short: the parent will, after a short pause, continue as if fork had 625In short: the parent will, after a short pause, continue as if fork had
562not been called, while the child will act as if IO::AIO has not been used 626not been called, while the child will act as if BDB has not been used
563yet. 627yet.
564 628
565=head2 MEMORY USAGE 629=head2 MEMORY USAGE
566 630
567Per-request usage: 631Per-request usage:
… …
570bytes of memory. In addition, stat requests need a stat buffer (possibly 634bytes of memory. In addition, stat requests need a stat buffer (possibly
571a few hundred bytes), readdir requires a result buffer and so on. Perl 635a few hundred bytes), readdir requires a result buffer and so on. Perl
572scalars and other data passed into aio requests will also be locked and 636scalars and other data passed into aio requests will also be locked and
573will consume memory till the request has entered the done state. 637will consume memory till the request has entered the done state.
574 638
575This is now awfully much, so queuing lots of requests is not usually a 639This is not awfully much, so queuing lots of requests is not usually a
576problem. 640problem.
577 641
578Per-thread usage: 642Per-thread usage:
579 643
580In the execution phase, some aio requests require more memory for 644In the execution phase, some aio requests require more memory for
581temporary buffers, and each thread requires a stack and other data 645temporary buffers, and each thread requires a stack and other data
582structures (usually around 16k-128k, depending on the OS). 646structures (usually around 16k-128k, depending on the OS).
583 647
584=head1 KNOWN BUGS 648=head1 KNOWN BUGS
585 649
586Known bugs will be fixed in the next release. 650Known bugs will be fixed in the next release, except:
651
652 If you use a transaction in any request, and the request returns
653 with an operating system error or DB_LOCK_NOTGRANTED, the internal
654 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
655 above.
587 656
588=head1 SEE ALSO 657=head1 SEE ALSO
589 658
590L<Coro::AIO>. 659L<Coro::BDB>, L<IO::AIO>.
591 660
592=head1 AUTHOR 661=head1 AUTHOR
593 662
594 Marc Lehmann <schmorp@schmorp.de> 663 Marc Lehmann <schmorp@schmorp.de>
595 http://home.schmorp.de/ 664 http://home.schmorp.de/

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