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Comparing BDB/BDB.pm (file contents):
Revision 1.15 by root, Thu Sep 13 21:34:00 2007 UTC vs.
Revision 1.46 by root, Thu Jul 17 12:09:56 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 = '1.1'; 116 $VERSION = '1.7';
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_open db_close db_compact db_sync db_upgrade
122 db_put db_exists db_get db_pget db_del db_key_range
83 db_txn_commit db_txn_abort db_txn_finish 123 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 124 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 125 db_sequence_open db_sequence_close
86 db_sequence_get db_sequence_remove 126 db_sequence_get db_sequence_remove
87 ); 127 );
… …
95 135
96 require XSLoader; 136 require XSLoader;
97 XSLoader::load ("BDB", $VERSION); 137 XSLoader::load ("BDB", $VERSION);
98} 138}
99 139
140=head2 WIN32 FILENAMES/DATABASE NAME MESS
141
142Perl on Win32 supports only ASCII filenames (the reason is that it abuses
143an internal flag to store wether a filename is Unicode or ANSI, but that
144flag is used for somethign else in the perl core, so there is no way to
145detect wether a filename is ANSI or Unicode-encoded). The BDB module
146tries to work around this issue by assuming that the filename is an ANSI
147filename and BDB was built for unicode support.
148
100=head2 BERKELEYDB FUNCTIONS 149=head2 BERKELEYDB FUNCTIONS
101 150
102All of these are functions. The create functions simply return a new 151All of these are functions. The create functions simply return a new
103object and never block. All the remaining functions all take an optional 152object and never block. All the remaining functions take an optional
104callback as last argument. If it is missing, then the fucntion will be 153callback as last argument. If it is missing, then the function will be
105executed synchronously. 154executed synchronously. In both cases, C<$!> will reflect the return value
155of the function.
106 156
107BDB functions that cannot block (mostly functions that manipulate 157BDB functions that cannot block (mostly functions that manipulate
108settings) are method calls on the relevant objects, so the rule of thumb 158settings) 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 159is: if it's a method, it's not blocking, if it's a function, it takes a
110callback as last argument. 160callback as last argument.
111 161
112In the following, C<$int> signifies an integer return value, 162In the following, C<$int> signifies an integer return value,
113C<octetstring> is a "binary string" (i.e. a perl string with no character 163C<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 164C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
115integer, C<NV> is a floating point value. 165floating point value.
116 166
117The C<SV *> types are generic perl scalars (for input and output of data 167Most 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 168values).
119when the request is completed.
120 169
121The various C<DB_ENV> etc. arguments are handles return by 170The 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 171C<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> 172appended C<_ornull> this means they are optional and you can pass C<undef>
124for them, resulting a NULL pointer on the C level. 173for them, resulting a NULL pointer on the C level.
125 174
175The C<SV *callback> is the optional callback function to call when the
176request is completed. This last callback argument is special: the callback
177is simply the last argument passed. If there are "optional" arguments
178before the callback they can be left out. The callback itself can be left
179out or specified as C<undef>, in which case the function will be executed
180synchronously.
181
182For example, C<db_env_txn_checkpoint> usually is called with all integer
183arguments zero. These can be left out, so all of these specify a call
184to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
185callback to be called:
186
187 db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
188 db_env_txn_checkpoint $db_env, 0, 0, sub { };
189 db_env_txn_checkpoint $db_env, sub { };
190
191While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
192executed synchronously:
193
194 db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
195 db_env_txn_checkpoint $db_env, 0, 0, 0;
196 db_env_txn_checkpoint $db_env, 0;
197
126=head3 BDB functions 198=head3 BDB functions
127 199
128Functions in the BDB namespace, exported by default: 200Functions in the BDB namespace, exported by default:
129 201
130 $env = db_env_create (U32 env_flags = 0) 202 $env = db_env_create (U32 env_flags = 0)
131 flags: RPCCLIENT 203 flags: RPCCLIENT
132 204
133 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 205 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 206 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) 207 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) 208 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
137 flags: FORCE 209 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) 210 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 211 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) 212 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) 213 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef)
214 db_env_dbremove (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
215 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)
142 216
143 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 217 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
144 flags: XA_CREATE 218 flags: XA_CREATE
145 219
146 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 220 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 221 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) 222 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
149 flags: DB_NOSYNC 223 flags: DB_NOSYNC
224 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) 225 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 226 flags: FREELIST_ONLY FREE_SPACE
152 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 227 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) 228 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) 229 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 230 flags: APPEND NODUPDATA NOOVERWRITE
231 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) 232 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 233 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) 234 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 235 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) 236 db_del (DB *db, DB_TXN_ornull *txn, SV *key, 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) 255 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
180 flags: TXN_NOSYNC 256 flags: TXN_NOSYNC
181 257
182=head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) 258=head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
183 259
184This is not a Berkeley DB function but a BDB module extension. It is very 260This is not actually a Berkeley DB function but a BDB module
261extension. The background for this exytension is: It is very annoying to
185annoying to have to check every single BDB function for error returns and 262have to check every single BDB function for error returns and provide a
186provide a codepath out of your transaction. While the BDB module still 263codepath out of your transaction. While the BDB module still makes this
187makes this possible, it contains the following extensions: 264possible, it contains the following extensions:
188 265
189When a transaction-protected function returns any operating system 266When a transaction-protected function returns any operating system
190error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the 267error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
191transaction. This flag is also set by Berkeley DB functions externally 268transaction. This flag is also set by Berkeley DB functions themselves
192when an operation fails with LOCK_DEADLOCK, and it causes all further 269when an operation fails with LOCK_DEADLOCK, and it causes all further
193operations on that transaction (including C<db_txn_commit>) to fail. 270operations on that transaction (including C<db_txn_commit>) to fail.
194 271
195The C<db_txn_finish> request will look at this flag, and, if it is set, 272The C<db_txn_finish> request will look at this flag, and, if it is set,
196will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK> 273will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
197if it isn't set). If it isn't set, it will call C<db_txn_commit> and 274if it isn't set to something else yet). If it isn't set, it will call
198return the error normally. 275C<db_txn_commit> and return the error normally.
199 276
200How to use this? Easy: just write your transaction normally: 277How to use this? Easy: just write your transaction normally:
201 278
202 my $txn = $db_env->txn_begin; 279 my $txn = $db_env->txn_begin;
203 db_get $db, $txn, "key", my $data; 280 db_get $db, $txn, "key", my $data;
… …
208That is, handle only the expected errors. If something unexpected happens 285That is, handle only the expected errors. If something unexpected happens
209(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining 286(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
210requests (db_put in this case) will simply be skipped (they will fail with 287requests (db_put in this case) will simply be skipped (they will fail with
211LOCK_DEADLOCK) and the transaction will be aborted. 288LOCK_DEADLOCK) and the transaction will be aborted.
212 289
213You cna use the C<< $txn->failed >> method to check wether a transaction 290You can use the C<< $txn->failed >> method to check wether a transaction
214has failed in this way and abort further processing (excluding 291has failed in this way and abort further processing (excluding
215C<db_txn_finish>). 292C<db_txn_finish>).
216 293
217=head3 DB_ENV/database environment methods 294=head3 DB_ENV/database environment methods
218 295
… …
226 $int = $env->set_data_dir (const char *dir) 303 $int = $env->set_data_dir (const char *dir)
227 $int = $env->set_tmp_dir (const char *dir) 304 $int = $env->set_tmp_dir (const char *dir)
228 $int = $env->set_lg_dir (const char *dir) 305 $int = $env->set_lg_dir (const char *dir)
229 $int = $env->set_shm_key (long shm_key) 306 $int = $env->set_shm_key (long shm_key)
230 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 307 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
231 $int = $env->set_flags (U32 flags, int onoff) 308 $int = $env->set_flags (U32 flags, int onoff = 1)
309 $int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
310 $int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
232 $env->set_errfile (FILE *errfile = 0) 311 $env->set_errfile (FILE *errfile = 0)
233 $env->set_msgfile (FILE *msgfile = 0) 312 $env->set_msgfile (FILE *msgfile = 0)
234 $int = $env->set_verbose (U32 which, int onoff = 1) 313 $int = $env->set_verbose (U32 which, int onoff = 1)
235 $int = $env->set_encrypt (const char *password, U32 flags = 0) 314 $int = $env->set_encrypt (const char *password, U32 flags = 0)
236 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) 315 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
… …
241 $int = $env->set_lk_max_lockers (U32 max) 320 $int = $env->set_lk_max_lockers (U32 max)
242 $int = $env->set_lk_max_locks (U32 max) 321 $int = $env->set_lk_max_locks (U32 max)
243 $int = $env->set_lk_max_objects (U32 max) 322 $int = $env->set_lk_max_objects (U32 max)
244 $int = $env->set_lg_bsize (U32 max) 323 $int = $env->set_lg_bsize (U32 max)
245 $int = $env->set_lg_max (U32 max) 324 $int = $env->set_lg_max (U32 max)
325 $int = $env->mutex_set_increment (U32 increment)
326 $int = $env->mutex_set_tas_spins (U32 tas_spins)
327 $int = $env->mutex_set_max (U32 max)
328 $int = $env->mutex_set_align (U32 align)
246 329
247 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 330 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
248 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC 331 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
332 $txn = $env->cdsgroup_begin; (v4.5)
249 333
250=head4 Example: 334=head4 Example:
251 335
252 use AnyEvent; 336 use AnyEvent;
253 use BDB; 337 use BDB;
… …
345 DESTROY (DBC_ornull *dbc) 429 DESTROY (DBC_ornull *dbc)
346 CODE: 430 CODE:
347 if (dbc) 431 if (dbc)
348 dbc->c_close (dbc); 432 dbc->c_close (dbc);
349 433
434 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
435
350=head4 Example: 436=head4 Example:
351 437
352 my $c = $db->cursor; 438 my $c = $db->cursor;
353 439
354 for (;;) { 440 for (;;) {
… …
387 473
388=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 474=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
389 475
390=over 4 476=over 4
391 477
478=item $msg = BDB::strerror [$errno]
479
480Returns the string corresponding to the given errno value. If no argument
481is given, use C<$!>.
482
483Note that the BDB module also patches the C<$!> variable directly, so you
484should be able to get a bdb error string by simply stringifying C<$!>.
485
392=item $fileno = BDB::poll_fileno 486=item $fileno = BDB::poll_fileno
393 487
394Return the I<request result pipe file descriptor>. This filehandle must be 488Return the I<request result pipe file descriptor>. This filehandle must be
395polled for reading by some mechanism outside this module (e.g. Event or 489polled for reading by some mechanism outside this module (e.g. Event or
396select, see below or the SYNOPSIS). If the pipe becomes readable you have 490select, see below or the SYNOPSIS). If the pipe becomes readable you have
… …
434interactiveness when perl is not fast enough to process all requests in 528interactiveness when perl is not fast enough to process all requests in
435time. 529time.
436 530
437For interactive programs, values such as C<0.01> to C<0.1> should be fine. 531For interactive programs, values such as C<0.01> to C<0.1> should be fine.
438 532
439Example: Install an Event watcher that automatically calls 533Example: Install an EV watcher that automatically calls
440BDB::poll_cb with low priority, to ensure that other parts of the 534BDB::poll_cb with low priority, to ensure that other parts of the
441program get the CPU sometimes even under high AIO load. 535program get the CPU sometimes even under high load.
442 536
443 # try not to spend much more than 0.1s in poll_cb 537 # try not to spend much more than 0.1s in poll_cb
444 BDB::max_poll_time 0.1; 538 BDB::max_poll_time 0.1;
445 539
446 # use a low priority so other tasks have priority 540 my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
447 Event->io (fd => BDB::poll_fileno,
448 poll => 'r', nice => 1,
449 cb => &BDB::poll_cb);
450 541
451=item BDB::poll_wait 542=item BDB::poll_wait
452 543
453If there are any outstanding requests and none of them in the result 544If there are any outstanding requests and none of them in the result
454phase, wait till the result filehandle becomes ready for reading (simply 545phase, wait till the result filehandle becomes ready for reading (simply
… …
466 557
467 BDB::poll_wait, BDB::poll_cb 558 BDB::poll_wait, BDB::poll_cb
468 559
469=item BDB::flush 560=item BDB::flush
470 561
471Wait till all outstanding AIO requests have been handled. 562Wait till all outstanding BDB requests have been handled.
472 563
473Strictly equivalent to: 564Strictly equivalent to:
474 565
475 BDB::poll_wait, BDB::poll_cb 566 BDB::poll_wait, BDB::poll_cb
476 while BDB::nreqs; 567 while BDB::nreqs;
477 568
478=back 569=back
479 570
571=head3 VERSION CHECKING
572
573BerkeleyDB comes in various versions, many of them have minor
574incompatibilities. This means that traditional "at least version x.x"
575checks are often not sufficient.
576
577Example: set the log_autoremove option in a way compatible with <v.47 and
578v4.7. Note the use of & on the constants to avoid triggering a compiletime
579bug when the symbol isn't available.
580
581 $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
582 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
583
584=over 4
585
586=item BDB::VERSION
587
588The C<BDB::VERSION> function, when called without arguments, returns the
589Berkeley DB version as a v-string (usually with 3 components). You should
590use C<lt> and C<ge> operators exclusively to make comparisons.
591
592Example: check for at least version 4.7.
593
594 BDB::VERSION ge v4.7 or die;
595
596=item BDB::VERSION min-version
597
598Returns true if the BDB version is at least the given version (specified
599as a v-string), false otherwise.
600
601Example: check for at least version 4.5.
602
603 BDB::VERSION v4.7 or die;
604
605=item BDB::VERSION min-version, max-version
606
607Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
608and less then C<max-version>.
609
610Example: check wether version is strictly less then v4.7.
611
612 BDB::VERSION v0, v4.7
613 or die "version 4.7 is not yet supported";
614
615=back
616
617=cut
618
619sub VERSION {
620 # I was dumb enough to override the VERSION method here, so let's try
621 # to fix it up.
622
623 if ($_[0] eq __PACKAGE__) {
624 $VERSION
625 } else {
626 if (@_ > 0) {
627 return undef if VERSION_v lt $_[0];
628 if (@_ > 1) {
629 return undef if VERSION_v ge $_[1];
630 }
631 }
632
633 VERSION_v
634 }
635}
636
480=head3 CONTROLLING THE NUMBER OF THREADS 637=head3 CONTROLLING THE NUMBER OF THREADS
481 638
482=over 4 639=over 4
483 640
484=item BDB::min_parallel $nthreads 641=item BDB::min_parallel $nthreads
485 642
486Set the minimum number of AIO threads to C<$nthreads>. The current 643Set the minimum number of BDB threads to C<$nthreads>. The current
487default is C<8>, which means eight asynchronous operations can execute 644default is C<8>, which means eight asynchronous operations can execute
488concurrently at any one time (the number of outstanding requests, 645concurrently at any one time (the number of outstanding requests,
489however, is unlimited). 646however, is unlimited).
490 647
491BDB starts threads only on demand, when an AIO request is queued and 648BDB starts threads only on demand, when an BDB request is queued and
492no free thread exists. Please note that queueing up a hundred requests can 649no free thread exists. Please note that queueing up a hundred requests can
493create demand for a hundred threads, even if it turns out that everything 650create demand for a hundred threads, even if it turns out that everything
494is in the cache and could have been processed faster by a single thread. 651is in the cache and could have been processed faster by a single thread.
495 652
496It is recommended to keep the number of threads relatively low, as some 653It is recommended to keep the number of threads relatively low, as some
… …
501Under most circumstances you don't need to call this function, as the 658Under most circumstances you don't need to call this function, as the
502module selects a default that is suitable for low to moderate load. 659module selects a default that is suitable for low to moderate load.
503 660
504=item BDB::max_parallel $nthreads 661=item BDB::max_parallel $nthreads
505 662
506Sets the maximum number of AIO threads to C<$nthreads>. If more than the 663Sets the maximum number of BDB threads to C<$nthreads>. If more than the
507specified number of threads are currently running, this function kills 664specified number of threads are currently running, this function kills
508them. This function blocks until the limit is reached. 665them. This function blocks until the limit is reached.
509 666
510While C<$nthreads> are zero, aio requests get queued but not executed 667While C<$nthreads> are zero, aio requests get queued but not executed
511until the number of threads has been increased again. 668until the number of threads has been increased again.
… …
550 707
551=item BDB::set_sync_prepare $cb 708=item BDB::set_sync_prepare $cb
552 709
553Sets a callback that is called whenever a request is created without an 710Sets a callback that is called whenever a request is created without an
554explicit callback. It has to return two code references. The first is used 711explicit callback. It has to return two code references. The first is used
555as the request callback, and the second is called to wait until the first 712as the request callback (it should save the return status), and the second
713is called to wait until the first callback has been called (it must set
714C<$!> to the return status).
715
716This mechanism can be used to include BDB into other event mechanisms,
717such as L<AnyEvent::BDB> or L<Coro::BDB>.
718
556callback has been called. The default implementation works like this: 719The default implementation works like this:
557 720
558 sub { 721 sub {
559 my $status; 722 my $status;
560 ( 723 (
561 sub { $status = $! }, 724 sub { $status = $! },
562 sub { BDB::poll while !defined $status; $! = $status }, 725 sub { BDB::poll while !defined $status; $! = $status },
563 ) 726 )
564 } 727 }
728
729It simply blocks the process till the request has finished and then sets
730C<$!> to the return value. This means that if you don't use a callback,
731BDB will simply fall back to synchronous operations.
565 732
566=back 733=back
567 734
568=head3 STATISTICAL INFORMATION 735=head3 STATISTICAL INFORMATION
569 736
… …
614 781
615=head2 FORK BEHAVIOUR 782=head2 FORK BEHAVIOUR
616 783
617This module should do "the right thing" when the process using it forks: 784This module should do "the right thing" when the process using it forks:
618 785
619Before the fork, IO::AIO enters a quiescent state where no requests 786Before the fork, BDB enters a quiescent state where no requests
620can be added in other threads and no results will be processed. After 787can be added in other threads and no results will be processed. After
621the fork the parent simply leaves the quiescent state and continues 788the fork the parent simply leaves the quiescent state and continues
622request/result processing, while the child frees the request/result queue 789request/result processing, while the child frees the request/result queue
623(so that the requests started before the fork will only be handled in the 790(so that the requests started before the fork will only be handled in the
624parent). Threads will be started on demand until the limit set in the 791parent). Threads will be started on demand until the limit set in the
625parent process has been reached again. 792parent process has been reached again.
626 793
627In short: the parent will, after a short pause, continue as if fork had 794In short: the parent will, after a short pause, continue as if fork had
628not been called, while the child will act as if IO::AIO has not been used 795not been called, while the child will act as if BDB has not been used
629yet. 796yet.
797
798Win32 note: there is no fork on win32, and perls emulation of it is too
799broken to be supported, so do not use BDB in a windows pseudo-fork, better
800yet, switch to a more capable platform.
630 801
631=head2 MEMORY USAGE 802=head2 MEMORY USAGE
632 803
633Per-request usage: 804Per-request usage:
634 805
… …
656 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, 827 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
657 above. 828 above.
658 829
659=head1 SEE ALSO 830=head1 SEE ALSO
660 831
661L<Coro::AIO>. 832L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
833syntax), L<IO::AIO> (nice to have).
662 834
663=head1 AUTHOR 835=head1 AUTHOR
664 836
665 Marc Lehmann <schmorp@schmorp.de> 837 Marc Lehmann <schmorp@schmorp.de>
666 http://home.schmorp.de/ 838 http://home.schmorp.de/

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