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Comparing BDB/BDB.pm (file contents):
Revision 1.13 by root, Mon Aug 13 12:07:55 2007 UTC vs.
Revision 1.44 by root, Wed Jul 9 21:08:29 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).
… …
72use strict 'vars'; 109use strict 'vars';
73 110
74use base 'Exporter'; 111use base 'Exporter';
75 112
76BEGIN { 113BEGIN {
77 our $VERSION = '1.0'; 114 our $VERSION = '1.7';
78 115
79 our @BDB_REQ = qw( 116 our @BDB_REQ = qw(
80 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect 117 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
81 db_env_memp_sync db_env_memp_trickle 118 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 119 db_open db_close db_compact db_sync db_upgrade
120 db_put db_exists db_get db_pget db_del db_key_range
83 db_txn_commit db_txn_abort 121 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 122 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 123 db_sequence_open db_sequence_close
86 db_sequence_get db_sequence_remove 124 db_sequence_get db_sequence_remove
87 ); 125 );
88 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create)); 126 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
… …
95 133
96 require XSLoader; 134 require XSLoader;
97 XSLoader::load ("BDB", $VERSION); 135 XSLoader::load ("BDB", $VERSION);
98} 136}
99 137
138=head2 WIN32 FILENAMES/DATABASE NAME MESS
139
140Perl on Win32 supports only ASCII filenames (the reason is that it abuses
141an internal flag to store wether a filename is Unicode or ANSI, but that
142flag is used for somethign else in the perl core, so there is no way to
143detect wether a filename is ANSI or Unicode-encoded). The BDB module
144tries to work around this issue by assuming that the filename is an ANSI
145filename and BDB was built for unicode support.
146
100=head2 BERKELEYDB FUNCTIONS 147=head2 BERKELEYDB FUNCTIONS
101 148
102All of these are functions. The create functions simply return a new 149All of these are functions. The create functions simply return a new
103object and never block. All the remaining functions all take an optional 150object and never block. All the remaining functions take an optional
104callback as last argument. If it is missing, then the fucntion will be 151callback as last argument. If it is missing, then the function will be
105executed synchronously. 152executed synchronously. In both cases, C<$!> will reflect the return value
153of the function.
106 154
107BDB functions that cannot block (mostly functions that manipulate 155BDB functions that cannot block (mostly functions that manipulate
108settings) are method calls on the relevant objects, so the rule of thumb 156settings) 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 157is: if it's a method, it's not blocking, if it's a function, it takes a
110callback as last argument. 158callback as last argument.
111 159
112In the following, C<$int> signifies an integer return value, 160In the following, C<$int> signifies an integer return value,
113C<octetstring> is a "binary string" (i.e. a perl string with no character 161C<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 162C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
115integer, C<NV> is a floating point value. 163floating point value.
116 164
117The C<SV *> types are generic perl scalars (for input and output of data 165Most 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 166values).
119when the request is completed.
120 167
121The various C<DB_ENV> etc. arguments are handles return by 168The 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 169C<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> 170appended C<_ornull> this means they are optional and you can pass C<undef>
124for them, resulting a NULL pointer on the C level. 171for them, resulting a NULL pointer on the C level.
125 172
173The C<SV *callback> is the optional callback function to call when the
174request is completed. This last callback argument is special: the callback
175is simply the last argument passed. If there are "optional" arguments
176before the callback they can be left out. The callback itself can be left
177out or specified as C<undef>, in which case the function will be executed
178synchronously.
179
180For example, C<db_env_txn_checkpoint> usually is called with all integer
181arguments zero. These can be left out, so all of these specify a call
182to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
183callback to be called:
184
185 db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
186 db_env_txn_checkpoint $db_env, 0, 0, sub { };
187 db_env_txn_checkpoint $db_env, sub { };
188
189While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
190executed synchronously:
191
192 db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
193 db_env_txn_checkpoint $db_env, 0, 0, 0;
194 db_env_txn_checkpoint $db_env, 0;
195
126=head3 BDB functions 196=head3 BDB functions
127 197
128Functions in the BDB namespace, exported by default: 198Functions in the BDB namespace, exported by default:
129 199
130 $env = db_env_create (U32 env_flags = 0) 200 $env = db_env_create (U32 env_flags = 0)
201 flags: RPCCLIENT
131 202
132 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 203 db_env_open (DB_ENV *env, bdb_filename db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef)
204 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) 205 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) 206 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
207 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) 208 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef)
209 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) 210 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) 211 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef)
212 db_env_dbremove (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
213 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)
138 214
139 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 215 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
216 flags: XA_CREATE
140 217
141 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 218 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)
219 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) 220 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
221 flags: DB_NOSYNC
222 db_upgrade (DB *db, bdb_filename file, U32 flags = 0, SV *callback = &PL_sv_undef)
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_undef) 223 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)
224 flags: FREELIST_ONLY FREE_SPACE
144 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 225 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) 226 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) 227 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
228 flags: APPEND NODUPDATA NOOVERWRITE
229 db_exists (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = 0)
147 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 230 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
231 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) 232 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
233 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) 234 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) 235 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
236 flags: TXN_NOSYNC TXN_SYNC
151 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 237 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef)
238
152 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 239 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) 240 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) 241 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
242 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) 243 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
244 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) 245 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) 246 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef)
158 247
159 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 248 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef)
249 flags: CREATE EXCL
160 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 250 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) 251 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)
252 flags: TXN_NOSYNC
162 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 253 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
254 flags: TXN_NOSYNC
163 255
256=head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
257
258This is not actually a Berkeley DB function but a BDB module
259extension. The background for this exytension is: It is very annoying to
260have to check every single BDB function for error returns and provide a
261codepath out of your transaction. While the BDB module still makes this
262possible, it contains the following extensions:
263
264When a transaction-protected function returns any operating system
265error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
266transaction. This flag is also set by Berkeley DB functions themselves
267when an operation fails with LOCK_DEADLOCK, and it causes all further
268operations on that transaction (including C<db_txn_commit>) to fail.
269
270The C<db_txn_finish> request will look at this flag, and, if it is set,
271will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
272if it isn't set to something else yet). If it isn't set, it will call
273C<db_txn_commit> and return the error normally.
274
275How to use this? Easy: just write your transaction normally:
276
277 my $txn = $db_env->txn_begin;
278 db_get $db, $txn, "key", my $data;
279 db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
280 db_txn_finish $txn;
281 die "transaction failed" if $!;
282
283That is, handle only the expected errors. If something unexpected happens
284(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
285requests (db_put in this case) will simply be skipped (they will fail with
286LOCK_DEADLOCK) and the transaction will be aborted.
287
288You can use the C<< $txn->failed >> method to check wether a transaction
289has failed in this way and abort further processing (excluding
290C<db_txn_finish>).
164 291
165=head3 DB_ENV/database environment methods 292=head3 DB_ENV/database environment methods
166 293
167Methods available on DB_ENV/$env handles: 294Methods available on DB_ENV/$env handles:
168 295
… …
174 $int = $env->set_data_dir (const char *dir) 301 $int = $env->set_data_dir (const char *dir)
175 $int = $env->set_tmp_dir (const char *dir) 302 $int = $env->set_tmp_dir (const char *dir)
176 $int = $env->set_lg_dir (const char *dir) 303 $int = $env->set_lg_dir (const char *dir)
177 $int = $env->set_shm_key (long shm_key) 304 $int = $env->set_shm_key (long shm_key)
178 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 305 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
179 $int = $env->set_flags (U32 flags, int onoff) 306 $int = $env->set_flags (U32 flags, int onoff = 1)
307 $int = $env->log_set_config (U32 flags, int onoff = 1) [v4.7]
308 $int = $env->set_intermediate_dir_mode (const char *modestring) [v4.7]
180 $env->set_errfile (FILE *errfile = 0) 309 $env->set_errfile (FILE *errfile = 0)
181 $env->set_msgfile (FILE *msgfile = 0) 310 $env->set_msgfile (FILE *msgfile = 0)
182 $int = $env->set_verbose (U32 which, int onoff = 1) 311 $int = $env->set_verbose (U32 which, int onoff = 1)
183 $int = $env->set_encrypt (const char *password, U32 flags = 0) 312 $int = $env->set_encrypt (const char *password, U32 flags = 0)
184 $int = $env->set_timeout (NV timeout, U32 flags) 313 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
185 $int = $env->set_mp_max_openfd (int maxopenfd); 314 $int = $env->set_mp_max_openfd (int maxopenfd);
186 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); 315 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
187 $int = $env->set_mp_mmapsize (int mmapsize_mb) 316 $int = $env->set_mp_mmapsize (int mmapsize_mb)
188 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) 317 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
189 $int = $env->set_lk_max_lockers (U32 max) 318 $int = $env->set_lk_max_lockers (U32 max)
190 $int = $env->set_lk_max_locks (U32 max) 319 $int = $env->set_lk_max_locks (U32 max)
191 $int = $env->set_lk_max_objects (U32 max) 320 $int = $env->set_lk_max_objects (U32 max)
192 $int = $env->set_lg_bsize (U32 max) 321 $int = $env->set_lg_bsize (U32 max)
193 $int = $env->set_lg_max (U32 max) 322 $int = $env->set_lg_max (U32 max)
323 $int = $env->mutex_set_increment (U32 increment)
324 $int = $env->mutex_set_tas_spins (U32 tas_spins)
325 $int = $env->mutex_set_max (U32 max)
326 $int = $env->mutex_set_align (U32 align)
194 327
195 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 328 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
329 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
330 $txn = $env->cdsgroup_begin;
196 331
197=head4 Example: 332=head4 Example:
198 333
199 use AnyEvent; 334 use AnyEvent;
200 use BDB; 335 use BDB;
… …
229 SvREFCNT_dec (env); 364 SvREFCNT_dec (env);
230 } 365 }
231 366
232 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 367 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
233 $int = $db->set_flags (U32 flags) 368 $int = $db->set_flags (U32 flags)
369 flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
370 Btree: DUP DUPSORT RECNUM REVSPLITOFF
371 Hash: DUP DUPSORT
372 Queue: INORDER
373 Recno: RENUMBER SNAPSHOT
374
234 $int = $db->set_encrypt (const char *password, U32 flags) 375 $int = $db->set_encrypt (const char *password, U32 flags)
235 $int = $db->set_lorder (int lorder) 376 $int = $db->set_lorder (int lorder)
236 $int = $db->set_bt_minkey (U32 minkey) 377 $int = $db->set_bt_minkey (U32 minkey)
237 $int = $db->set_re_delim (int delim) 378 $int = $db->set_re_delim (int delim)
238 $int = $db->set_re_pad (int re_pad) 379 $int = $db->set_re_pad (int re_pad)
… …
241 $int = $db->set_h_ffactor (U32 h_ffactor) 382 $int = $db->set_h_ffactor (U32 h_ffactor)
242 $int = $db->set_h_nelem (U32 h_nelem) 383 $int = $db->set_h_nelem (U32 h_nelem)
243 $int = $db->set_q_extentsize (U32 extentsize) 384 $int = $db->set_q_extentsize (U32 extentsize)
244 385
245 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 386 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
387 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
246 $seq = $db->sequence (U32 flags = 0) 388 $seq = $db->sequence (U32 flags = 0)
247 389
248=head4 Example: 390=head4 Example:
249 391
250 my $db = db_create $env; 392 my $db = db_create $env;
… …
269 DESTROY (DB_TXN_ornull *txn) 411 DESTROY (DB_TXN_ornull *txn)
270 CODE: 412 CODE:
271 if (txn) 413 if (txn)
272 txn->abort (txn); 414 txn->abort (txn);
273 415
274 $int = $txn->set_timeout (NV timeout, U32 flags) 416 $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
417 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
418
419 $bool = $txn->failed
420 # see db_txn_finish documentation, above
275 421
276 422
277=head3 DBC/cursor methods 423=head3 DBC/cursor methods
278 424
279Methods available on DBC/$dbc handles: 425Methods available on DBC/$dbc handles:
280 426
281 DESTROY (DBC_ornull *dbc) 427 DESTROY (DBC_ornull *dbc)
282 CODE: 428 CODE:
283 if (dbc) 429 if (dbc)
284 dbc->c_close (dbc); 430 dbc->c_close (dbc);
431
432 $int = $cursor->set_priority ($priority = PRIORITY_*)
285 433
286=head4 Example: 434=head4 Example:
287 435
288 my $c = $db->cursor; 436 my $c = $db->cursor;
289 437
… …
306 seq->close (seq, 0); 454 seq->close (seq, 0);
307 455
308 $int = $seq->initial_value (db_seq_t value) 456 $int = $seq->initial_value (db_seq_t value)
309 $int = $seq->set_cachesize (U32 size) 457 $int = $seq->set_cachesize (U32 size)
310 $int = $seq->set_flags (U32 flags) 458 $int = $seq->set_flags (U32 flags)
459 flags: SEQ_DEC SEQ_INC SEQ_WRAP
311 $int = $seq->set_range (db_seq_t min, db_seq_t max) 460 $int = $seq->set_range (db_seq_t min, db_seq_t max)
312 461
313=head4 Example: 462=head4 Example:
314 463
315 my $seq = $db->sequence; 464 my $seq = $db->sequence;
… …
321=head2 SUPPORT FUNCTIONS 470=head2 SUPPORT FUNCTIONS
322 471
323=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 472=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
324 473
325=over 4 474=over 4
475
476=item $msg = BDB::strerror [$errno]
477
478Returns the string corresponding to the given errno value. If no argument
479is given, use C<$!>.
480
481Note that the BDB module also patches the C<$!> variable directly, so you
482should be able to get a bdb error string by simply stringifying C<$!>.
326 483
327=item $fileno = BDB::poll_fileno 484=item $fileno = BDB::poll_fileno
328 485
329Return the I<request result pipe file descriptor>. This filehandle must be 486Return the I<request result pipe file descriptor>. This filehandle must be
330polled for reading by some mechanism outside this module (e.g. Event or 487polled for reading by some mechanism outside this module (e.g. Event or
… …
369interactiveness when perl is not fast enough to process all requests in 526interactiveness when perl is not fast enough to process all requests in
370time. 527time.
371 528
372For interactive programs, values such as C<0.01> to C<0.1> should be fine. 529For interactive programs, values such as C<0.01> to C<0.1> should be fine.
373 530
374Example: Install an Event watcher that automatically calls 531Example: Install an EV watcher that automatically calls
375BDB::poll_cb with low priority, to ensure that other parts of the 532BDB::poll_cb with low priority, to ensure that other parts of the
376program get the CPU sometimes even under high AIO load. 533program get the CPU sometimes even under high load.
377 534
378 # try not to spend much more than 0.1s in poll_cb 535 # try not to spend much more than 0.1s in poll_cb
379 BDB::max_poll_time 0.1; 536 BDB::max_poll_time 0.1;
380 537
381 # use a low priority so other tasks have priority 538 my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
382 Event->io (fd => BDB::poll_fileno,
383 poll => 'r', nice => 1,
384 cb => &BDB::poll_cb);
385 539
386=item BDB::poll_wait 540=item BDB::poll_wait
387 541
388If there are any outstanding requests and none of them in the result 542If there are any outstanding requests and none of them in the result
389phase, wait till the result filehandle becomes ready for reading (simply 543phase, wait till the result filehandle becomes ready for reading (simply
… …
401 555
402 BDB::poll_wait, BDB::poll_cb 556 BDB::poll_wait, BDB::poll_cb
403 557
404=item BDB::flush 558=item BDB::flush
405 559
406Wait till all outstanding AIO requests have been handled. 560Wait till all outstanding BDB requests have been handled.
407 561
408Strictly equivalent to: 562Strictly equivalent to:
409 563
410 BDB::poll_wait, BDB::poll_cb 564 BDB::poll_wait, BDB::poll_cb
411 while BDB::nreqs; 565 while BDB::nreqs;
412 566
413=back 567=back
414 568
569=head3 VERSION CHECKING
570
571BerkeleyDB comes in various versions, many of them have minor
572incompatibilities. This means that traditional "at least version x.x"
573checks are often not sufficient.
574
575Example: set the log_autoremove option in a way compatible with <v.47 and
576v4.7. Note the use of & on the constants to avoid triggering a compiletime
577bug when the symbol isn't available.
578
579 $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
580 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
581
582=over 4
583
584=item BDB::VERSION
585
586The C<BDB::VERSION> function, when called without arguments, returns the
587Berkeley DB version as a v-string (usually with 3 components). You should
588use C<lt> and C<ge> operators exclusively to make comparisons.
589
590Example: check for at least version 4.7.
591
592 BDB::VERSION ge v4.7 or die;
593
594=item BDB::VERSION min-version
595
596Returns true if the BDB version is at least the given version (specified
597as a v-string), false otherwise.
598
599Example: check for at least version 4.5.
600
601 BDB::VERSION v4.7 or die;
602
603=item BDB::VERSION min-version, max-version
604
605Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
606and less then C<max-version>.
607
608Example: check wether version is strictly less then v4.7.
609
610 BDB::VERSION v0, v4.7
611 or die "version 4.7 is not yet supported";
612
613=back
614
615=cut
616
617sub VERSION {
618 if (@_ > 0) {
619 return undef if VERSION_v lt $_[0];
620 if (@_ > 1) {
621 return undef if VERSION_v ge $_[1];
622 }
623 }
624
625 VERSION_v
626}
627
415=head3 CONTROLLING THE NUMBER OF THREADS 628=head3 CONTROLLING THE NUMBER OF THREADS
416 629
417=over 4 630=over 4
418 631
419=item BDB::min_parallel $nthreads 632=item BDB::min_parallel $nthreads
420 633
421Set the minimum number of AIO threads to C<$nthreads>. The current 634Set the minimum number of BDB threads to C<$nthreads>. The current
422default is C<8>, which means eight asynchronous operations can execute 635default is C<8>, which means eight asynchronous operations can execute
423concurrently at any one time (the number of outstanding requests, 636concurrently at any one time (the number of outstanding requests,
424however, is unlimited). 637however, is unlimited).
425 638
426BDB starts threads only on demand, when an AIO request is queued and 639BDB starts threads only on demand, when an BDB request is queued and
427no free thread exists. Please note that queueing up a hundred requests can 640no free thread exists. Please note that queueing up a hundred requests can
428create demand for a hundred threads, even if it turns out that everything 641create demand for a hundred threads, even if it turns out that everything
429is in the cache and could have been processed faster by a single thread. 642is in the cache and could have been processed faster by a single thread.
430 643
431It is recommended to keep the number of threads relatively low, as some 644It is recommended to keep the number of threads relatively low, as some
… …
436Under most circumstances you don't need to call this function, as the 649Under most circumstances you don't need to call this function, as the
437module selects a default that is suitable for low to moderate load. 650module selects a default that is suitable for low to moderate load.
438 651
439=item BDB::max_parallel $nthreads 652=item BDB::max_parallel $nthreads
440 653
441Sets the maximum number of AIO threads to C<$nthreads>. If more than the 654Sets the maximum number of BDB threads to C<$nthreads>. If more than the
442specified number of threads are currently running, this function kills 655specified number of threads are currently running, this function kills
443them. This function blocks until the limit is reached. 656them. This function blocks until the limit is reached.
444 657
445While C<$nthreads> are zero, aio requests get queued but not executed 658While C<$nthreads> are zero, aio requests get queued but not executed
446until the number of threads has been increased again. 659until the number of threads has been increased again.
… …
485 698
486=item BDB::set_sync_prepare $cb 699=item BDB::set_sync_prepare $cb
487 700
488Sets a callback that is called whenever a request is created without an 701Sets a callback that is called whenever a request is created without an
489explicit callback. It has to return two code references. The first is used 702explicit callback. It has to return two code references. The first is used
490as the request callback, and the second is called to wait until the first 703as the request callback (it should save the return status), and the second
704is called to wait until the first callback has been called (it must set
705C<$!> to the return status).
706
707This mechanism can be used to include BDB into other event mechanisms,
708such as L<AnyEvent::BDB> or L<Coro::BDB>.
709
491callback has been called. The default implementation works like this: 710The default implementation works like this:
492 711
493 sub { 712 sub {
494 my $status; 713 my $status;
495 ( 714 (
496 sub { $status = $! }, 715 sub { $status = $! },
497 sub { BDB::poll while !defined $status; $! = $status }, 716 sub { BDB::poll while !defined $status; $! = $status },
498 ) 717 )
499 } 718 }
719
720It simply blocks the process till the request has finished and then sets
721C<$!> to the return value. This means that if you don't use a callback,
722BDB will simply fall back to synchronous operations.
500 723
501=back 724=back
502 725
503=head3 STATISTICAL INFORMATION 726=head3 STATISTICAL INFORMATION
504 727
… …
549 772
550=head2 FORK BEHAVIOUR 773=head2 FORK BEHAVIOUR
551 774
552This module should do "the right thing" when the process using it forks: 775This module should do "the right thing" when the process using it forks:
553 776
554Before the fork, IO::AIO enters a quiescent state where no requests 777Before the fork, BDB enters a quiescent state where no requests
555can be added in other threads and no results will be processed. After 778can be added in other threads and no results will be processed. After
556the fork the parent simply leaves the quiescent state and continues 779the fork the parent simply leaves the quiescent state and continues
557request/result processing, while the child frees the request/result queue 780request/result processing, while the child frees the request/result queue
558(so that the requests started before the fork will only be handled in the 781(so that the requests started before the fork will only be handled in the
559parent). Threads will be started on demand until the limit set in the 782parent). Threads will be started on demand until the limit set in the
560parent process has been reached again. 783parent process has been reached again.
561 784
562In short: the parent will, after a short pause, continue as if fork had 785In short: the parent will, after a short pause, continue as if fork had
563not been called, while the child will act as if IO::AIO has not been used 786not been called, while the child will act as if BDB has not been used
564yet. 787yet.
788
789Win32 note: there is no fork on win32, and perls emulation of it is too
790broken to be supported, so do not use BDB in a windows pseudo-fork, better
791yet, switch to a more capable platform.
565 792
566=head2 MEMORY USAGE 793=head2 MEMORY USAGE
567 794
568Per-request usage: 795Per-request usage:
569 796
… …
582temporary buffers, and each thread requires a stack and other data 809temporary buffers, and each thread requires a stack and other data
583structures (usually around 16k-128k, depending on the OS). 810structures (usually around 16k-128k, depending on the OS).
584 811
585=head1 KNOWN BUGS 812=head1 KNOWN BUGS
586 813
587Known bugs will be fixed in the next release. 814Known bugs will be fixed in the next release, except:
815
816 If you use a transaction in any request, and the request returns
817 with an operating system error or DB_LOCK_NOTGRANTED, the internal
818 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
819 above.
588 820
589=head1 SEE ALSO 821=head1 SEE ALSO
590 822
591L<Coro::AIO>. 823L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
824syntax), L<IO::AIO> (nice to have).
592 825
593=head1 AUTHOR 826=head1 AUTHOR
594 827
595 Marc Lehmann <schmorp@schmorp.de> 828 Marc Lehmann <schmorp@schmorp.de>
596 http://home.schmorp.de/ 829 http://home.schmorp.de/

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