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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 1.53 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 = '1.1'; 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 a Berkeley DB function but a BDB module extension. It is very 253This is not actually a Berkeley DB function but a BDB module
254extension. The background for this exytension is: It is very annoying to
185annoying to have to check every single BDB function for error returns and 255have to check every single BDB function for error returns and provide a
186provide a codepath out of your transaction. While the BDB module still 256codepath out of your transaction. While the BDB module still makes this
187makes this possible, it contains the following extensions: 257possible, it contains the following extensions:
188 258
189When a transaction-protected function returns any operating system 259When a transaction-protected function returns any operating system
190error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the 260error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
191transaction. This flag is also set by Berkeley DB functions externally 261transaction. This flag is also set by Berkeley DB functions themselves
192when an operation fails with LOCK_DEADLOCK, and it causes all further 262when an operation fails with LOCK_DEADLOCK, and it causes all further
193operations on that transaction (including C<db_txn_commit>) to fail. 263operations on that transaction (including C<db_txn_commit>) to fail.
194 264
195The C<db_txn_finish> request will look at this flag, and, if it is set, 265The 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> 266will 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 267if it isn't set to something else yet). If it isn't set, it will call
198return the error normally. 268C<db_txn_commit> and return the error normally.
199 269
200How to use this? Easy: just write your transaction normally: 270How to use this? Easy: just write your transaction normally:
201 271
202 my $txn = $db_env->txn_begin; 272 my $txn = $db_env->txn_begin;
203 db_get $db, $txn, "key", my $data; 273 db_get $db, $txn, "key", my $data;
… …
208That is, handle only the expected errors. If something unexpected happens 278That 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 279(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 280requests (db_put in this case) will simply be skipped (they will fail with
211LOCK_DEADLOCK) and the transaction will be aborted. 281LOCK_DEADLOCK) and the transaction will be aborted.
212 282
213You cna use the C<< $txn->failed >> method to check wether a transaction 283You can use the C<< $txn->failed >> method to check wether a transaction
214has failed in this way and abort further processing (excluding 284has failed in this way and abort further processing (excluding
215C<db_txn_finish>). 285C<db_txn_finish>).
216 286
217=head3 DB_ENV/database environment methods 287=head2 DB_ENV/database environment methods
218 288
219Methods available on DB_ENV/$env handles: 289Methods available on DB_ENV/$env handles:
220 290
221 DESTROY (DB_ENV_ornull *env) 291 DESTROY (DB_ENV_ornull *env)
222 CODE: 292 CODE:
… …
226 $int = $env->set_data_dir (const char *dir) 296 $int = $env->set_data_dir (const char *dir)
227 $int = $env->set_tmp_dir (const char *dir) 297 $int = $env->set_tmp_dir (const char *dir)
228 $int = $env->set_lg_dir (const char *dir) 298 $int = $env->set_lg_dir (const char *dir)
229 $int = $env->set_shm_key (long shm_key) 299 $int = $env->set_shm_key (long shm_key)
230 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 300 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
231 $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)
232 $env->set_errfile (FILE *errfile = 0) 304 $env->set_errfile (FILE *errfile = 0)
233 $env->set_msgfile (FILE *msgfile = 0) 305 $env->set_msgfile (FILE *msgfile = 0)
234 $int = $env->set_verbose (U32 which, int onoff = 1) 306 $int = $env->set_verbose (U32 which, int onoff = 1)
235 $int = $env->set_encrypt (const char *password, U32 flags = 0) 307 $int = $env->set_encrypt (const char *password, U32 flags = 0)
236 $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)
… …
241 $int = $env->set_lk_max_lockers (U32 max) 313 $int = $env->set_lk_max_lockers (U32 max)
242 $int = $env->set_lk_max_locks (U32 max) 314 $int = $env->set_lk_max_locks (U32 max)
243 $int = $env->set_lk_max_objects (U32 max) 315 $int = $env->set_lk_max_objects (U32 max)
244 $int = $env->set_lg_bsize (U32 max) 316 $int = $env->set_lg_bsize (U32 max)
245 $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)
246 322
247 $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)
248 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)
249 326
250=head4 Example: 327=head3 Example:
251 328
252 use AnyEvent; 329 use AnyEvent;
253 use BDB; 330 use BDB;
254 331
255 our $FH; open $FH, "<&=" . BDB::poll_fileno; 332 our $FH; open $FH, "<&=" . BDB::poll_fileno;
… …
267 0600; 344 0600;
268 345
269 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 346 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
270 347
271 348
272=head3 DB/database methods 349=head2 DB/database methods
273 350
274Methods available on DB/$db handles: 351Methods available on DB/$db handles:
275 352
276 DESTROY (DB_ornull *db) 353 DESTROY (DB_ornull *db)
277 CODE: 354 CODE:
… …
303 380
304 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 381 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
305 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT 382 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
306 $seq = $db->sequence (U32 flags = 0) 383 $seq = $db->sequence (U32 flags = 0)
307 384
308=head4 Example: 385=head3 Example:
309 386
310 my $db = db_create $env; 387 my $db = db_create $env;
311 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;
312 389
313 for (1..1000) { 390 for (1..1000) {
… …
320 db_del $db, undef, "key $_" for 1..1000; 397 db_del $db, undef, "key $_" for 1..1000;
321 398
322 db_sync $db; 399 db_sync $db;
323 400
324 401
325=head3 DB_TXN/transaction methods 402=head2 DB_TXN/transaction methods
326 403
327Methods available on DB_TXN/$txn handles: 404Methods available on DB_TXN/$txn handles:
328 405
329 DESTROY (DB_TXN_ornull *txn) 406 DESTROY (DB_TXN_ornull *txn)
330 CODE: 407 CODE:
… …
336 413
337 $bool = $txn->failed 414 $bool = $txn->failed
338 # see db_txn_finish documentation, above 415 # see db_txn_finish documentation, above
339 416
340 417
341=head3 DBC/cursor methods 418=head2 DBC/cursor methods
342 419
343Methods available on DBC/$dbc handles: 420Methods available on DBC/$dbc handles:
344 421
345 DESTROY (DBC_ornull *dbc) 422 DESTROY (DBC_ornull *dbc)
346 CODE: 423 CODE:
347 if (dbc) 424 if (dbc)
348 dbc->c_close (dbc); 425 dbc->c_close (dbc);
349 426
427 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
428
350=head4 Example: 429=head3 Example:
351 430
352 my $c = $db->cursor; 431 my $c = $db->cursor;
353 432
354 for (;;) { 433 for (;;) {
355 db_c_get $c, my $key, my $data, BDB::NEXT; 434 db_c_get $c, my $key, my $data, BDB::NEXT;
… …
358 } 437 }
359 438
360 db_c_close $c; 439 db_c_close $c;
361 440
362 441
363=head3 DB_SEQUENCE/sequence methods 442=head2 DB_SEQUENCE/sequence methods
364 443
365Methods available on DB_SEQUENCE/$seq handles: 444Methods available on DB_SEQUENCE/$seq handles:
366 445
367 DESTROY (DB_SEQUENCE_ornull *seq) 446 DESTROY (DB_SEQUENCE_ornull *seq)
368 CODE: 447 CODE:
… …
373 $int = $seq->set_cachesize (U32 size) 452 $int = $seq->set_cachesize (U32 size)
374 $int = $seq->set_flags (U32 flags) 453 $int = $seq->set_flags (U32 flags)
375 flags: SEQ_DEC SEQ_INC SEQ_WRAP 454 flags: SEQ_DEC SEQ_INC SEQ_WRAP
376 $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)
377 456
378=head4 Example: 457=head3 Example:
379 458
380 my $seq = $db->sequence; 459 my $seq = $db->sequence;
381 460
382 db_sequence_open $seq, undef, "seq", BDB::CREATE; 461 db_sequence_open $seq, undef, "seq", BDB::CREATE;
383 db_sequence_get $seq, undef, 1, my $value; 462 db_sequence_get $seq, undef, 1, my $value;
384 463
385 464
386=head2 SUPPORT FUNCTIONS 465=head1 SUPPORT FUNCTIONS
387 466
388=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 467=head2 EVENT PROCESSING AND EVENT LOOP INTEGRATION
389 468
390=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<$!>.
391 478
392=item $fileno = BDB::poll_fileno 479=item $fileno = BDB::poll_fileno
393 480
394Return the I<request result pipe file descriptor>. This filehandle must be 481Return the I<request result pipe file descriptor>. This filehandle must be
395polled 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
… …
434interactiveness when perl is not fast enough to process all requests in 521interactiveness when perl is not fast enough to process all requests in
435time. 522time.
436 523
437For interactive programs, values such as C<0.01> to C<0.1> should be fine. 524For interactive programs, values such as C<0.01> to C<0.1> should be fine.
438 525
439Example: Install an Event watcher that automatically calls 526Example: Install an EV watcher that automatically calls
440BDB::poll_cb with low priority, to ensure that other parts of the 527BDB::poll_cb with low priority, to ensure that other parts of the
441program get the CPU sometimes even under high AIO load. 528program get the CPU sometimes even under high load.
442 529
443 # try not to spend much more than 0.1s in poll_cb 530 # try not to spend much more than 0.1s in poll_cb
444 BDB::max_poll_time 0.1; 531 BDB::max_poll_time 0.1;
445 532
446 # use a low priority so other tasks have priority 533 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);
450 534
451=item BDB::poll_wait 535=item BDB::poll_wait
452 536
453If there are any outstanding requests and none of them in the result 537If there are any outstanding requests and none of them in the result
454phase, wait till the result filehandle becomes ready for reading (simply 538phase, wait till the result filehandle becomes ready for reading (simply
… …
466 550
467 BDB::poll_wait, BDB::poll_cb 551 BDB::poll_wait, BDB::poll_cb
468 552
469=item BDB::flush 553=item BDB::flush
470 554
471Wait till all outstanding AIO requests have been handled. 555Wait till all outstanding BDB requests have been handled.
472 556
473Strictly equivalent to: 557Strictly equivalent to:
474 558
475 BDB::poll_wait, BDB::poll_cb 559 BDB::poll_wait, BDB::poll_cb
476 while BDB::nreqs; 560 while BDB::nreqs;
477 561
478=back 562=back
479 563
480=head3 CONTROLLING THE NUMBER OF THREADS 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 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
481 576
482=over 4 577=over 4
483 578
579=item BDB::VERSION
580
581The C<BDB::VERSION> function, when called without arguments, returns the
582Berkeley DB version as a v-string (usually with 3 components). You should
583use C<lt> and C<ge> operators exclusively to make comparisons.
584
585Example: check for at least version 4.7.
586
587 BDB::VERSION ge v4.7 or die;
588
589=item BDB::VERSION min-version
590
591Returns true if the BDB version is at least the given version (specified
592as a v-string), false otherwise.
593
594Example: check for at least version 4.5.
595
596 BDB::VERSION v4.7 or die;
597
598=item BDB::VERSION min-version, max-version
599
600Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
601and less then C<max-version>.
602
603Example: check wether version is strictly less then v4.7.
604
605 BDB::VERSION v0, v4.7
606 or die "version 4.7 is not yet supported";
607
608=back
609
610=cut
611
612sub VERSION {
613 # I was dumb enough to override the VERSION method here, so let's try
614 # to fix it up.
615
616 if ($_[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
630=head2 CONTROLLING THE NUMBER OF THREADS
631
632=over 4
633
484=item BDB::min_parallel $nthreads 634=item BDB::min_parallel $nthreads
485 635
486Set the minimum number of AIO threads to C<$nthreads>. The current 636Set the minimum number of BDB threads to C<$nthreads>. The current
487default is C<8>, which means eight asynchronous operations can execute 637default is C<8>, which means eight asynchronous operations can execute
488concurrently at any one time (the number of outstanding requests, 638concurrently at any one time (the number of outstanding requests,
489however, is unlimited). 639however, is unlimited).
490 640
491BDB starts threads only on demand, when an AIO request is queued and 641BDB 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 642no 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 643create 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. 644is in the cache and could have been processed faster by a single thread.
495 645
496It is recommended to keep the number of threads relatively low, as some 646It 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 651Under most circumstances you don't need to call this function, as the
502module selects a default that is suitable for low to moderate load. 652module selects a default that is suitable for low to moderate load.
503 653
504=item BDB::max_parallel $nthreads 654=item BDB::max_parallel $nthreads
505 655
506Sets the maximum number of AIO threads to C<$nthreads>. If more than the 656Sets the maximum number of BDB threads to C<$nthreads>. If more than the
507specified number of threads are currently running, this function kills 657specified number of threads are currently running, this function kills
508them. This function blocks until the limit is reached. 658them. This function blocks until the limit is reached.
509 659
510While C<$nthreads> are zero, aio requests get queued but not executed 660While C<$nthreads> are zero, aio requests get queued but not executed
511until the number of threads has been increased again. 661until the number of threads has been increased again.
… …
546 696
547You can still queue as many requests as you want. Therefore, 697You can still queue as many requests as you want. Therefore,
548C<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
549as 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).
550 700
551=item BDB::set_sync_prepare $cb 701=item $old_cb = BDB::set_sync_prepare $cb
552 702
553Sets a callback that is called whenever a request is created without an 703Sets a callback that is called whenever a request is created without an
554explicit callback. It has to return two code references. The first is used 704explicit callback. It has to return two code references. The first is used
555as the request callback, and the second is called to wait until the first 705as the request callback (it should save the return status), and the second
556callback has been called. The default implementation works like this: 706is called to wait until the first callback has been called (it must set
707C<$!> 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:
557 714
558 sub { 715 sub {
559 my $status; 716 my $status;
560 ( 717 (
561 sub { $status = $! }, 718 sub { $status = $! },
562 sub { BDB::poll while !defined $status; $! = $status }, 719 sub { BDB::poll while !defined $status; $! = $status },
563 ) 720 )
564 } 721 }
565 722
723It works by polling for results till the request has finished and then
724sets C<$!> 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
566=back 731=back
567 732
568=head3 STATISTICAL INFORMATION 733=head2 STATISTICAL INFORMATION
569 734
570=over 4 735=over 4
571 736
572=item BDB::nreqs 737=item BDB::nreqs
573 738
… …
591 756
592=back 757=back
593 758
594=cut 759=cut
595 760
596set_sync_prepare { 761set_sync_prepare (undef);
597 my $status;
598 (
599 sub {
600 $status = $!;
601 },
602 sub {
603 BDB::poll while !defined $status;
604 $! = $status;
605 },
606 )
607};
608 762
609min_parallel 8; 763min_parallel 8;
610 764
611END { flush } 765END { flush }
612 766
6131; 7671;
614 768
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
615=head2 FORK BEHAVIOUR 792=head1 FORK BEHAVIOUR
616 793
617This 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:
618 795
619Before the fork, IO::AIO enters a quiescent state where no requests 796Before the fork, BDB enters a quiescent state where no requests
620can 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
621the fork the parent simply leaves the quiescent state and continues 798the fork the parent simply leaves the quiescent state and continues
622request/result processing, while the child frees the request/result queue 799request/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 800(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 801parent). Threads will be started on demand until the limit set in the
625parent process has been reached again. 802parent process has been reached again.
626 803
627In 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
628not been called, while the child will act as if IO::AIO has not been used 805not been called, while the child will act as if BDB has not been used
629yet. 806yet.
630 807
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
631=head2 MEMORY USAGE 812=head1 MEMORY USAGE
632 813
633Per-request usage: 814Per-request usage:
634 815
635Each aio request uses - depending on your architecture - around 100-200 816Each aio request uses - depending on your architecture - around 100-200
636bytes of memory. In addition, stat requests need a stat buffer (possibly 817bytes of memory. In addition, stat requests need a stat buffer (possibly
… …
645 826
646In the execution phase, some aio requests require more memory for 827In the execution phase, some aio requests require more memory for
647temporary buffers, and each thread requires a stack and other data 828temporary buffers, and each thread requires a stack and other data
648structures (usually around 16k-128k, depending on the OS). 829structures (usually around 16k-128k, depending on the OS).
649 830
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
650=head1 KNOWN BUGS 840=head1 KNOWN BUGS
651 841
652Known bugs will be fixed in the next release, except: 842Known bugs will be fixed in the next release, except:
653 843
654 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
… …
656 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>,
657 above. 847 above.
658 848
659=head1 SEE ALSO 849=head1 SEE ALSO
660 850
661L<Coro::AIO>. 851L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
852syntax), L<IO::AIO> (nice to have).
662 853
663=head1 AUTHOR 854=head1 AUTHOR
664 855
665 Marc Lehmann <schmorp@schmorp.de> 856 Marc Lehmann <schmorp@schmorp.de>
666 http://home.schmorp.de/ 857 http://home.schmorp.de/

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