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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 1.53 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 = '1.0'; 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 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 );
88 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create)); 129 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
… …
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)
195 flags: RPCCLIENT
131 196
132 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)
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
133 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)
134 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)
201 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) 202 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef)
203 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) 204 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) 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)
138 209
139 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 210 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
211 flags: XA_CREATE
140 212
141 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)
214 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) 215 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
216 flags: DB_NOSYNC
217 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) 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)
219 flags: FREELIST_ONLY FREE_SPACE
144 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)
145 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)
146 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)
223 flags: APPEND NODUPDATA NOOVERWRITE
224 db_exists (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = 0) (v4.6)
147 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)
226 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) 227 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
228 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) 229 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) 230 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
231 flags: TXN_NOSYNC TXN_SYNC
151 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 232 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef)
233
152 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 234 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) 235 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) 236 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
237 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) 238 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
239 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) 240 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) 241 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef)
158 242
159 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 243 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef)
244 flags: CREATE EXCL
160 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 245 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) 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)
247 flags: TXN_NOSYNC
162 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)
249 flags: TXN_NOSYNC
163 250
251=head3 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
164 252
253This is not actually a Berkeley DB function but a BDB module
254extension. The background for this exytension is: It is very annoying to
255have to check every single BDB function for error returns and provide a
256codepath out of your transaction. While the BDB module still makes this
257possible, it contains the following extensions:
258
259When a transaction-protected function returns any operating system
260error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
261transaction. This flag is also set by Berkeley DB functions themselves
262when an operation fails with LOCK_DEADLOCK, and it causes all further
263operations on that transaction (including C<db_txn_commit>) to fail.
264
265The C<db_txn_finish> request will look at this flag, and, if it is set,
266will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
267if it isn't set to something else yet). If it isn't set, it will call
268C<db_txn_commit> and return the error normally.
269
270How to use this? Easy: just write your transaction normally:
271
272 my $txn = $db_env->txn_begin;
273 db_get $db, $txn, "key", my $data;
274 db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
275 db_txn_finish $txn;
276 die "transaction failed" if $!;
277
278That is, handle only the expected errors. If something unexpected happens
279(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
280requests (db_put in this case) will simply be skipped (they will fail with
281LOCK_DEADLOCK) and the transaction will be aborted.
282
283You can use the C<< $txn->failed >> method to check wether a transaction
284has failed in this way and abort further processing (excluding
285C<db_txn_finish>).
286
165=head3 DB_ENV/database environment methods 287=head2 DB_ENV/database environment methods
166 288
167Methods available on DB_ENV/$env handles: 289Methods available on DB_ENV/$env handles:
168 290
169 DESTROY (DB_ENV_ornull *env) 291 DESTROY (DB_ENV_ornull *env)
170 CODE: 292 CODE:
… …
174 $int = $env->set_data_dir (const char *dir) 296 $int = $env->set_data_dir (const char *dir)
175 $int = $env->set_tmp_dir (const char *dir) 297 $int = $env->set_tmp_dir (const char *dir)
176 $int = $env->set_lg_dir (const char *dir) 298 $int = $env->set_lg_dir (const char *dir)
177 $int = $env->set_shm_key (long shm_key) 299 $int = $env->set_shm_key (long shm_key)
178 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 300 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
179 $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)
180 $env->set_errfile (FILE *errfile = 0) 304 $env->set_errfile (FILE *errfile = 0)
181 $env->set_msgfile (FILE *msgfile = 0) 305 $env->set_msgfile (FILE *msgfile = 0)
182 $int = $env->set_verbose (U32 which, int onoff = 1) 306 $int = $env->set_verbose (U32 which, int onoff = 1)
183 $int = $env->set_encrypt (const char *password, U32 flags = 0) 307 $int = $env->set_encrypt (const char *password, U32 flags = 0)
184 $int = $env->set_timeout (NV timeout, U32 flags) 308 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
185 $int = $env->set_mp_max_openfd (int maxopenfd); 309 $int = $env->set_mp_max_openfd (int maxopenfd);
186 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); 310 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
187 $int = $env->set_mp_mmapsize (int mmapsize_mb) 311 $int = $env->set_mp_mmapsize (int mmapsize_mb)
188 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) 312 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
189 $int = $env->set_lk_max_lockers (U32 max) 313 $int = $env->set_lk_max_lockers (U32 max)
190 $int = $env->set_lk_max_locks (U32 max) 314 $int = $env->set_lk_max_locks (U32 max)
191 $int = $env->set_lk_max_objects (U32 max) 315 $int = $env->set_lk_max_objects (U32 max)
192 $int = $env->set_lg_bsize (U32 max) 316 $int = $env->set_lg_bsize (U32 max)
193 $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)
194 322
195 $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)
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)
196 326
197=head4 Example: 327=head3 Example:
198 328
199 use AnyEvent; 329 use AnyEvent;
200 use BDB; 330 use BDB;
201 331
202 our $FH; open $FH, "<&=" . BDB::poll_fileno; 332 our $FH; open $FH, "<&=" . BDB::poll_fileno;
… …
214 0600; 344 0600;
215 345
216 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 346 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
217 347
218 348
219=head3 DB/database methods 349=head2 DB/database methods
220 350
221Methods available on DB/$db handles: 351Methods available on DB/$db handles:
222 352
223 DESTROY (DB_ornull *db) 353 DESTROY (DB_ornull *db)
224 CODE: 354 CODE:
… …
229 SvREFCNT_dec (env); 359 SvREFCNT_dec (env);
230 } 360 }
231 361
232 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 362 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
233 $int = $db->set_flags (U32 flags) 363 $int = $db->set_flags (U32 flags)
364 flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
365 Btree: DUP DUPSORT RECNUM REVSPLITOFF
366 Hash: DUP DUPSORT
367 Queue: INORDER
368 Recno: RENUMBER SNAPSHOT
369
234 $int = $db->set_encrypt (const char *password, U32 flags) 370 $int = $db->set_encrypt (const char *password, U32 flags)
235 $int = $db->set_lorder (int lorder) 371 $int = $db->set_lorder (int lorder)
236 $int = $db->set_bt_minkey (U32 minkey) 372 $int = $db->set_bt_minkey (U32 minkey)
237 $int = $db->set_re_delim (int delim) 373 $int = $db->set_re_delim (int delim)
238 $int = $db->set_re_pad (int re_pad) 374 $int = $db->set_re_pad (int re_pad)
… …
241 $int = $db->set_h_ffactor (U32 h_ffactor) 377 $int = $db->set_h_ffactor (U32 h_ffactor)
242 $int = $db->set_h_nelem (U32 h_nelem) 378 $int = $db->set_h_nelem (U32 h_nelem)
243 $int = $db->set_q_extentsize (U32 extentsize) 379 $int = $db->set_q_extentsize (U32 extentsize)
244 380
245 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 381 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
382 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
246 $seq = $db->sequence (U32 flags = 0) 383 $seq = $db->sequence (U32 flags = 0)
247 384
248=head4 Example: 385=head3 Example:
249 386
250 my $db = db_create $env; 387 my $db = db_create $env;
251 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;
252 389
253 for (1..1000) { 390 for (1..1000) {
… …
260 db_del $db, undef, "key $_" for 1..1000; 397 db_del $db, undef, "key $_" for 1..1000;
261 398
262 db_sync $db; 399 db_sync $db;
263 400
264 401
265=head3 DB_TXN/transaction methods 402=head2 DB_TXN/transaction methods
266 403
267Methods available on DB_TXN/$txn handles: 404Methods available on DB_TXN/$txn handles:
268 405
269 DESTROY (DB_TXN_ornull *txn) 406 DESTROY (DB_TXN_ornull *txn)
270 CODE: 407 CODE:
271 if (txn) 408 if (txn)
272 txn->abort (txn); 409 txn->abort (txn);
273 410
274 $int = $txn->set_timeout (NV timeout, U32 flags) 411 $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
412 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
275 413
414 $bool = $txn->failed
415 # see db_txn_finish documentation, above
276 416
417
277=head3 DBC/cursor methods 418=head2 DBC/cursor methods
278 419
279Methods available on DBC/$dbc handles: 420Methods available on DBC/$dbc handles:
280 421
281 DESTROY (DBC_ornull *dbc) 422 DESTROY (DBC_ornull *dbc)
282 CODE: 423 CODE:
283 if (dbc) 424 if (dbc)
284 dbc->c_close (dbc); 425 dbc->c_close (dbc);
285 426
427 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
428
286=head4 Example: 429=head3 Example:
287 430
288 my $c = $db->cursor; 431 my $c = $db->cursor;
289 432
290 for (;;) { 433 for (;;) {
291 db_c_get $c, my $key, my $data, BDB::NEXT; 434 db_c_get $c, my $key, my $data, BDB::NEXT;
… …
294 } 437 }
295 438
296 db_c_close $c; 439 db_c_close $c;
297 440
298 441
299=head3 DB_SEQUENCE/sequence methods 442=head2 DB_SEQUENCE/sequence methods
300 443
301Methods available on DB_SEQUENCE/$seq handles: 444Methods available on DB_SEQUENCE/$seq handles:
302 445
303 DESTROY (DB_SEQUENCE_ornull *seq) 446 DESTROY (DB_SEQUENCE_ornull *seq)
304 CODE: 447 CODE:
… …
306 seq->close (seq, 0); 449 seq->close (seq, 0);
307 450
308 $int = $seq->initial_value (db_seq_t value) 451 $int = $seq->initial_value (db_seq_t value)
309 $int = $seq->set_cachesize (U32 size) 452 $int = $seq->set_cachesize (U32 size)
310 $int = $seq->set_flags (U32 flags) 453 $int = $seq->set_flags (U32 flags)
454 flags: SEQ_DEC SEQ_INC SEQ_WRAP
311 $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)
312 456
313=head4 Example: 457=head3 Example:
314 458
315 my $seq = $db->sequence; 459 my $seq = $db->sequence;
316 460
317 db_sequence_open $seq, undef, "seq", BDB::CREATE; 461 db_sequence_open $seq, undef, "seq", BDB::CREATE;
318 db_sequence_get $seq, undef, 1, my $value; 462 db_sequence_get $seq, undef, 1, my $value;
319 463
320 464
321=head2 SUPPORT FUNCTIONS 465=head1 SUPPORT FUNCTIONS
322 466
323=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 467=head2 EVENT PROCESSING AND EVENT LOOP INTEGRATION
324 468
325=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<$!>.
326 478
327=item $fileno = BDB::poll_fileno 479=item $fileno = BDB::poll_fileno
328 480
329Return the I<request result pipe file descriptor>. This filehandle must be 481Return the I<request result pipe file descriptor>. This filehandle must be
330polled 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
… …
369interactiveness when perl is not fast enough to process all requests in 521interactiveness when perl is not fast enough to process all requests in
370time. 522time.
371 523
372For 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.
373 525
374Example: Install an Event watcher that automatically calls 526Example: Install an EV watcher that automatically calls
375BDB::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
376program get the CPU sometimes even under high AIO load. 528program get the CPU sometimes even under high load.
377 529
378 # 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
379 BDB::max_poll_time 0.1; 531 BDB::max_poll_time 0.1;
380 532
381 # use a low priority so other tasks have priority 533 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);
385 534
386=item BDB::poll_wait 535=item BDB::poll_wait
387 536
388If 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
389phase, wait till the result filehandle becomes ready for reading (simply 538phase, wait till the result filehandle becomes ready for reading (simply
… …
401 550
402 BDB::poll_wait, BDB::poll_cb 551 BDB::poll_wait, BDB::poll_cb
403 552
404=item BDB::flush 553=item BDB::flush
405 554
406Wait till all outstanding AIO requests have been handled. 555Wait till all outstanding BDB requests have been handled.
407 556
408Strictly equivalent to: 557Strictly equivalent to:
409 558
410 BDB::poll_wait, BDB::poll_cb 559 BDB::poll_wait, BDB::poll_cb
411 while BDB::nreqs; 560 while BDB::nreqs;
412 561
413=back 562=back
414 563
415=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 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
416 576
417=over 4 577=over 4
418 578
579=item BDB::VERSION
580
581The C<BDB::VERSION> function, when called without arguments, returns the
582Berkeley DB version as a v-string (usually with 3 components). You should
583use C<lt> and C<ge> operators exclusively to make comparisons.
584
585Example: check for at least version 4.7.
586
587 BDB::VERSION ge v4.7 or die;
588
589=item BDB::VERSION min-version
590
591Returns true if the BDB version is at least the given version (specified
592as a v-string), false otherwise.
593
594Example: check for at least version 4.5.
595
596 BDB::VERSION v4.7 or die;
597
598=item BDB::VERSION min-version, max-version
599
600Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
601and less then C<max-version>.
602
603Example: check wether version is strictly less then v4.7.
604
605 BDB::VERSION v0, v4.7
606 or die "version 4.7 is not yet supported";
607
608=back
609
610=cut
611
612sub VERSION {
613 # I was dumb enough to override the VERSION method here, so let's try
614 # to fix it up.
615
616 if ($_[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
419=item BDB::min_parallel $nthreads 634=item BDB::min_parallel $nthreads
420 635
421Set the minimum number of AIO threads to C<$nthreads>. The current 636Set the minimum number of BDB threads to C<$nthreads>. The current
422default is C<8>, which means eight asynchronous operations can execute 637default is C<8>, which means eight asynchronous operations can execute
423concurrently at any one time (the number of outstanding requests, 638concurrently at any one time (the number of outstanding requests,
424however, is unlimited). 639however, is unlimited).
425 640
426BDB 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
427no 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
428create 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
429is 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.
430 645
431It 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
… …
436Under 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
437module selects a default that is suitable for low to moderate load. 652module selects a default that is suitable for low to moderate load.
438 653
439=item BDB::max_parallel $nthreads 654=item BDB::max_parallel $nthreads
440 655
441Sets the maximum number of AIO threads to C<$nthreads>. If more than the 656Sets the maximum number of BDB threads to C<$nthreads>. If more than the
442specified number of threads are currently running, this function kills 657specified number of threads are currently running, this function kills
443them. This function blocks until the limit is reached. 658them. This function blocks until the limit is reached.
444 659
445While C<$nthreads> are zero, aio requests get queued but not executed 660While C<$nthreads> are zero, aio requests get queued but not executed
446until the number of threads has been increased again. 661until the number of threads has been increased again.
… …
481 696
482You can still queue as many requests as you want. Therefore, 697You can still queue as many requests as you want. Therefore,
483C<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
484as 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).
485 700
486=item BDB::set_sync_prepare $cb 701=item $old_cb = BDB::set_sync_prepare $cb
487 702
488Sets a callback that is called whenever a request is created without an 703Sets a callback that is called whenever a request is created without an
489explicit callback. It has to return two code references. The first is used 704explicit callback. It has to return two code references. The first is used
490as the request callback, and the second is called to wait until the first 705as the request callback (it should save the return status), and the second
491callback has been called. The default implementation works like this: 706is called to wait until the first callback has been called (it must set
707C<$!> 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:
492 714
493 sub { 715 sub {
494 my $status; 716 my $status;
495 ( 717 (
496 sub { $status = $! }, 718 sub { $status = $! },
497 sub { BDB::poll while !defined $status; $! = $status }, 719 sub { BDB::poll while !defined $status; $! = $status },
498 ) 720 )
499 } 721 }
500 722
723It works by polling for results till the request has finished and then
724sets C<$!> 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
501=back 731=back
502 732
503=head3 STATISTICAL INFORMATION 733=head2 STATISTICAL INFORMATION
504 734
505=over 4 735=over 4
506 736
507=item BDB::nreqs 737=item BDB::nreqs
508 738
… …
526 756
527=back 757=back
528 758
529=cut 759=cut
530 760
531set_sync_prepare { 761set_sync_prepare (undef);
532 my $status;
533 (
534 sub {
535 $status = $!;
536 },
537 sub {
538 BDB::poll while !defined $status;
539 $! = $status;
540 },
541 )
542};
543 762
544min_parallel 8; 763min_parallel 8;
545 764
546END { flush } 765END { flush }
547 766
5481; 7671;
549 768
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
550=head2 FORK BEHAVIOUR 792=head1 FORK BEHAVIOUR
551 793
552This 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:
553 795
554Before the fork, IO::AIO enters a quiescent state where no requests 796Before the fork, BDB enters a quiescent state where no requests
555can 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
556the fork the parent simply leaves the quiescent state and continues 798the fork the parent simply leaves the quiescent state and continues
557request/result processing, while the child frees the request/result queue 799request/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 800(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 801parent). Threads will be started on demand until the limit set in the
560parent process has been reached again. 802parent process has been reached again.
561 803
562In 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
563not 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
564yet. 806yet.
565 807
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
566=head2 MEMORY USAGE 812=head1 MEMORY USAGE
567 813
568Per-request usage: 814Per-request usage:
569 815
570Each aio request uses - depending on your architecture - around 100-200 816Each aio request uses - depending on your architecture - around 100-200
571bytes of memory. In addition, stat requests need a stat buffer (possibly 817bytes of memory. In addition, stat requests need a stat buffer (possibly
… …
580 826
581In the execution phase, some aio requests require more memory for 827In the execution phase, some aio requests require more memory for
582temporary buffers, and each thread requires a stack and other data 828temporary buffers, and each thread requires a stack and other data
583structures (usually around 16k-128k, depending on the OS). 829structures (usually around 16k-128k, depending on the OS).
584 830
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
585=head1 KNOWN BUGS 840=head1 KNOWN BUGS
586 841
587Known bugs will be fixed in the next release. 842Known bugs will be fixed in the next release, except:
843
844 If you use a transaction in any request, and the request returns
845 with an operating system error or DB_LOCK_NOTGRANTED, the internal
846 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
847 above.
588 848
589=head1 SEE ALSO 849=head1 SEE ALSO
590 850
591L<Coro::AIO>. 851L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
852syntax), L<IO::AIO> (nice to have).
592 853
593=head1 AUTHOR 854=head1 AUTHOR
594 855
595 Marc Lehmann <schmorp@schmorp.de> 856 Marc Lehmann <schmorp@schmorp.de>
596 http://home.schmorp.de/ 857 http://home.schmorp.de/

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