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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 1.68 by root, Tue Feb 2 04:17:03 2016 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 integration 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).
… …
66 103
67=cut 104=cut
68 105
69package BDB; 106package BDB;
70 107
71no warnings; 108use common::sense;
72use strict 'vars';
73 109
74use base 'Exporter'; 110use base 'Exporter';
75 111
112our $VERSION;
113
76BEGIN { 114BEGIN {
77 our $VERSION = '1.0'; 115 $VERSION = '1.91';
78 116
79 our @BDB_REQ = qw( 117 our @BDB_REQ = qw(
80 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect 118 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
81 db_env_memp_sync db_env_memp_trickle 119 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 120 db_env_log_archive db_env_lsn_reset
121 db_open db_close db_compact db_sync db_verify db_upgrade
122 db_put db_exists db_get db_pget db_del db_key_range
83 db_txn_commit db_txn_abort 123 db_txn_commit db_txn_abort db_txn_finish
84 db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del 124 db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
85 db_sequence_open db_sequence_close 125 db_sequence_open db_sequence_close
86 db_sequence_get db_sequence_remove 126 db_sequence_get db_sequence_remove
87 ); 127 );
88 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create)); 128 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
… …
95 135
96 require XSLoader; 136 require XSLoader;
97 XSLoader::load ("BDB", $VERSION); 137 XSLoader::load ("BDB", $VERSION);
98} 138}
99 139
100=head2 BERKELEYDB FUNCTIONS 140=head1 BERKELEYDB FUNCTIONS
101 141
102All of these are functions. The create functions simply return a new 142All of these are functions. The create functions simply return a new
103object and never block. All the remaining functions all take an optional 143object and never block. All the remaining functions take an optional
104callback as last argument. If it is missing, then the fucntion will be 144callback as last argument. If it is missing, then the function will be
105executed synchronously. 145executed synchronously. In both cases, C<$!> will reflect the return value
146of the function.
106 147
107BDB functions that cannot block (mostly functions that manipulate 148BDB functions that cannot block (mostly functions that manipulate
108settings) are method calls on the relevant objects, so the rule of thumb 149settings) 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 150is: if it's a method, it's not blocking, if it's a function, it takes a
110callback as last argument. 151callback as last argument.
111 152
112In the following, C<$int> signifies an integer return value, 153In the following, C<$int> signifies an integer return value,
113C<octetstring> is a "binary string" (i.e. a perl string with no character 154C<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 155C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
115integer, C<NV> is a floating point value. 156floating point value.
116 157
117The C<SV *> types are generic perl scalars (for input and output of data 158Most 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 159values).
119when the request is completed.
120 160
121The various C<DB_ENV> etc. arguments are handles return by 161The 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 162C<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> 163appended C<_ornull> this means they are optional and you can pass C<undef>
124for them, resulting a NULL pointer on the C level. 164for them, resulting a NULL pointer on the C level.
125 165
166The C<SV *callback> is the optional callback function to call when the
167request is completed. This last callback argument is special: the callback
168is simply the last argument passed. If there are "optional" arguments
169before the callback they can be left out. The callback itself can be left
170out or specified as C<undef>, in which case the function will be executed
171synchronously.
172
173For example, C<db_env_txn_checkpoint> usually is called with all integer
174arguments zero. These can be left out, so all of these specify a call
175to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
176callback to be called:
177
178 db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
179 db_env_txn_checkpoint $db_env, 0, 0, sub { };
180 db_env_txn_checkpoint $db_env, sub { };
181
182While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
183executed synchronously:
184
185 db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
186 db_env_txn_checkpoint $db_env, 0, 0, 0;
187 db_env_txn_checkpoint $db_env, 0;
188
126=head3 BDB functions 189=head2 BDB functions
127 190
128Functions in the BDB namespace, exported by default: 191Functions in the BDB namespace, exported by default:
129 192
130 $env = db_env_create (U32 env_flags = 0) 193 $env = db_env_create (U32 env_flags = 0)
194 flags: RPCCLIENT
131 195
132 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 196 db_env_open (DB_ENV *env, bdb_filename db_home, U32 open_flags, int mode, SV *callback = 0)
197 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) 198 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = 0)
134 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 199 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = 0)
200 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) 201 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = 0)
202 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) 203 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = 0)
137 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) 204 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = 0)
205 db_env_dbremove (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = 0)
206 db_env_dbrename (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = 0)
207 db_env_log_archive (DB_ENV *env, SV *listp, U32 flags = 0, SV *callback = 0)
208 db_env_lsn_reset (DB_ENV *env, bdb_filename db, U32 flags = 0, SV *callback = 0)
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 = 0)
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 = 0)
216 flags: DB_NOSYNC
217 db_verify (DB *db, bdb_filename file, bdb_filename database = 0, SV *dummy = 0, U32 flags = 0, SV *callback = 0)
218 db_upgrade (DB *db, bdb_filename file, U32 flags = 0, SV *callback = 0)
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) 219 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 = 0)
220 flags: FREELIST_ONLY FREE_SPACE
144 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 221 db_sync (DB *db, U32 flags = 0, SV *callback = 0)
145 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) 222 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = 0)
146 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 223 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
224 flags: APPEND NODUPDATA NOOVERWRITE
225 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) 226 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
227 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) 228 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = 0)
229 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) 230 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = 0)
150 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) 231 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = 0)
232 flags: TXN_NOSYNC TXN_SYNC
151 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 233 db_txn_abort (DB_TXN *txn, SV *callback = 0)
234
152 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 235 db_c_close (DBC *dbc, SV *callback = 0)
153 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) 236 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = 0)
154 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 237 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
238 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) 239 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
240 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) 241 db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = 0)
157 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef) 242 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = 0)
158 243
159 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 244 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = 0)
245 flags: CREATE EXCL
160 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 246 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = 0)
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) 247 db_sequence_get (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, int delta, SV *seq_value, U32 flags = DB_TXN_NOSYNC, SV *callback = 0)
248 flags: TXN_NOSYNC
162 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 249 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = 0)
250 flags: TXN_NOSYNC
163 251
252=head3 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = 0)
164 253
254This is not actually a Berkeley DB function but a BDB module
255extension. The background for this exytension is: It is very annoying to
256have to check every single BDB function for error returns and provide a
257codepath out of your transaction. While the BDB module still makes this
258possible, it contains the following extensions:
259
260When a transaction-protected function returns any operating system
261error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
262transaction. This flag is also set by Berkeley DB functions themselves
263when an operation fails with LOCK_DEADLOCK, and it causes all further
264operations on that transaction (including C<db_txn_commit>) to fail.
265
266The C<db_txn_finish> request will look at this flag, and, if it is set,
267will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
268if it isn't set to something else yet). If it isn't set, it will call
269C<db_txn_commit> and return the error normally.
270
271How to use this? Easy: just write your transaction normally:
272
273 my $txn = $db_env->txn_begin;
274 db_get $db, $txn, "key", my $data;
275 db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
276 db_txn_finish $txn;
277 die "transaction failed" if $!;
278
279That is, handle only the expected errors. If something unexpected happens
280(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
281requests (db_put in this case) will simply be skipped (they will fail with
282LOCK_DEADLOCK) and the transaction will be aborted.
283
284You can use the C<< $txn->failed >> method to check wether a transaction
285has failed in this way and abort further processing (excluding
286C<db_txn_finish>).
287
288
165=head3 DB_ENV/database environment methods 289=head2 DB_ENV/database environment methods
166 290
167Methods available on DB_ENV/$env handles: 291Methods available on DB_ENV/$env handles:
168 292
169 DESTROY (DB_ENV_ornull *env) 293 DESTROY (DB_ENV_ornull *env)
170 CODE: 294 CODE:
… …
174 $int = $env->set_data_dir (const char *dir) 298 $int = $env->set_data_dir (const char *dir)
175 $int = $env->set_tmp_dir (const char *dir) 299 $int = $env->set_tmp_dir (const char *dir)
176 $int = $env->set_lg_dir (const char *dir) 300 $int = $env->set_lg_dir (const char *dir)
177 $int = $env->set_shm_key (long shm_key) 301 $int = $env->set_shm_key (long shm_key)
178 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 302 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
179 $int = $env->set_flags (U32 flags, int onoff) 303 $int = $env->set_flags (U32 flags, int onoff = 1)
304 $int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
305 $int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
180 $env->set_errfile (FILE *errfile = 0) 306 $env->set_errfile (FILE *errfile = 0)
181 $env->set_msgfile (FILE *msgfile = 0) 307 $env->set_msgfile (FILE *msgfile = 0)
182 $int = $env->set_verbose (U32 which, int onoff = 1) 308 $int = $env->set_verbose (U32 which, int onoff = 1)
183 $int = $env->set_encrypt (const char *password, U32 flags = 0) 309 $int = $env->set_encrypt (const char *password, U32 flags = 0)
184 $int = $env->set_timeout (NV timeout, U32 flags) 310 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
185 $int = $env->set_mp_max_openfd (int maxopenfd); 311 $int = $env->set_mp_max_openfd (int maxopenfd);
186 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); 312 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
187 $int = $env->set_mp_mmapsize (int mmapsize_mb) 313 $int = $env->set_mp_mmapsize (int mmapsize_mb)
188 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) 314 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
189 $int = $env->set_lk_max_lockers (U32 max) 315 $int = $env->set_lk_max_lockers (U32 max)
190 $int = $env->set_lk_max_locks (U32 max) 316 $int = $env->set_lk_max_locks (U32 max)
191 $int = $env->set_lk_max_objects (U32 max) 317 $int = $env->set_lk_max_objects (U32 max)
192 $int = $env->set_lg_bsize (U32 max) 318 $int = $env->set_lg_bsize (U32 max)
193 $int = $env->set_lg_max (U32 max) 319 $int = $env->set_lg_max (U32 max)
320 $int = $env->mutex_set_increment (U32 increment)
321 $int = $env->mutex_set_tas_spins (U32 tas_spins)
322 $int = $env->mutex_set_max (U32 max)
323 $int = $env->mutex_set_align (U32 align)
194 324
195 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 325 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
326 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
327 $txn = $env->cdsgroup_begin; (v4.5)
196 328
197=head4 Example: 329=head3 Example:
198 330
199 use AnyEvent; 331 use AnyEvent;
200 use BDB; 332 use BDB;
201 333
202 our $FH; open $FH, "<&=" . BDB::poll_fileno; 334 our $FH; open $FH, "<&=" . BDB::poll_fileno;
… …
214 0600; 346 0600;
215 347
216 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 348 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
217 349
218 350
219=head3 DB/database methods 351=head2 DB/database methods
220 352
221Methods available on DB/$db handles: 353Methods available on DB/$db handles:
222 354
223 DESTROY (DB_ornull *db) 355 DESTROY (DB_ornull *db)
224 CODE: 356 CODE:
… …
229 SvREFCNT_dec (env); 361 SvREFCNT_dec (env);
230 } 362 }
231 363
232 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 364 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
233 $int = $db->set_flags (U32 flags) 365 $int = $db->set_flags (U32 flags)
366 flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
367 Btree: DUP DUPSORT RECNUM REVSPLITOFF
368 Hash: DUP DUPSORT
369 Queue: INORDER
370 Recno: RENUMBER SNAPSHOT
371
234 $int = $db->set_encrypt (const char *password, U32 flags) 372 $int = $db->set_encrypt (const char *password, U32 flags)
235 $int = $db->set_lorder (int lorder) 373 $int = $db->set_lorder (int lorder)
236 $int = $db->set_bt_minkey (U32 minkey) 374 $int = $db->set_bt_minkey (U32 minkey)
237 $int = $db->set_re_delim (int delim) 375 $int = $db->set_re_delim (int delim)
238 $int = $db->set_re_pad (int re_pad) 376 $int = $db->set_re_pad (int re_pad)
… …
241 $int = $db->set_h_ffactor (U32 h_ffactor) 379 $int = $db->set_h_ffactor (U32 h_ffactor)
242 $int = $db->set_h_nelem (U32 h_nelem) 380 $int = $db->set_h_nelem (U32 h_nelem)
243 $int = $db->set_q_extentsize (U32 extentsize) 381 $int = $db->set_q_extentsize (U32 extentsize)
244 382
245 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 383 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
384 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
246 $seq = $db->sequence (U32 flags = 0) 385 $seq = $db->sequence (U32 flags = 0)
247 386
248=head4 Example: 387=head3 Example:
249 388
250 my $db = db_create $env; 389 my $db = db_create $env;
251 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600; 390 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600;
252 391
253 for (1..1000) { 392 for (1..1000) {
… …
260 db_del $db, undef, "key $_" for 1..1000; 399 db_del $db, undef, "key $_" for 1..1000;
261 400
262 db_sync $db; 401 db_sync $db;
263 402
264 403
265=head3 DB_TXN/transaction methods 404=head2 DB_TXN/transaction methods
266 405
267Methods available on DB_TXN/$txn handles: 406Methods available on DB_TXN/$txn handles:
268 407
269 DESTROY (DB_TXN_ornull *txn) 408 DESTROY (DB_TXN_ornull *txn)
270 CODE: 409 CODE:
271 if (txn) 410 if (txn)
272 txn->abort (txn); 411 txn->abort (txn);
273 412
274 $int = $txn->set_timeout (NV timeout, U32 flags) 413 $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
414 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
275 415
416 $bool = $txn->failed
417 # see db_txn_finish documentation, above
276 418
419
277=head3 DBC/cursor methods 420=head2 DBC/cursor methods
278 421
279Methods available on DBC/$dbc handles: 422Methods available on DBC/$dbc handles:
280 423
281 DESTROY (DBC_ornull *dbc) 424 DESTROY (DBC_ornull *dbc)
282 CODE: 425 CODE:
283 if (dbc) 426 if (dbc)
284 dbc->c_close (dbc); 427 dbc->c_close (dbc);
285 428
429 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
430
286=head4 Example: 431=head3 Example:
287 432
288 my $c = $db->cursor; 433 my $c = $db->cursor;
289 434
290 for (;;) { 435 for (;;) {
291 db_c_get $c, my $key, my $data, BDB::NEXT; 436 db_c_get $c, my $key, my $data, BDB::NEXT;
… …
294 } 439 }
295 440
296 db_c_close $c; 441 db_c_close $c;
297 442
298 443
299=head3 DB_SEQUENCE/sequence methods 444=head2 DB_SEQUENCE/sequence methods
300 445
301Methods available on DB_SEQUENCE/$seq handles: 446Methods available on DB_SEQUENCE/$seq handles:
302 447
303 DESTROY (DB_SEQUENCE_ornull *seq) 448 DESTROY (DB_SEQUENCE_ornull *seq)
304 CODE: 449 CODE:
… …
306 seq->close (seq, 0); 451 seq->close (seq, 0);
307 452
308 $int = $seq->initial_value (db_seq_t value) 453 $int = $seq->initial_value (db_seq_t value)
309 $int = $seq->set_cachesize (U32 size) 454 $int = $seq->set_cachesize (U32 size)
310 $int = $seq->set_flags (U32 flags) 455 $int = $seq->set_flags (U32 flags)
456 flags: SEQ_DEC SEQ_INC SEQ_WRAP
311 $int = $seq->set_range (db_seq_t min, db_seq_t max) 457 $int = $seq->set_range (db_seq_t min, db_seq_t max)
312 458
313=head4 Example: 459=head3 Example:
314 460
315 my $seq = $db->sequence; 461 my $seq = $db->sequence;
316 462
317 db_sequence_open $seq, undef, "seq", BDB::CREATE; 463 db_sequence_open $seq, undef, "seq", BDB::CREATE;
318 db_sequence_get $seq, undef, 1, my $value; 464 db_sequence_get $seq, undef, 1, my $value;
319 465
320 466
321=head2 SUPPORT FUNCTIONS 467=head1 SUPPORT FUNCTIONS
322 468
323=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 469=head2 EVENT PROCESSING AND EVENT LOOP INTEGRATION
324 470
325=over 4 471=over 4
472
473=item $msg = BDB::strerror [$errno]
474
475Returns the string corresponding to the given errno value. If no argument
476is given, use C<$!>.
477
478Note that the BDB module also patches the C<$!> variable directly, so you
479should be able to get a bdb error string by simply stringifying C<$!>.
326 480
327=item $fileno = BDB::poll_fileno 481=item $fileno = BDB::poll_fileno
328 482
329Return the I<request result pipe file descriptor>. This filehandle must be 483Return the I<request result pipe file descriptor>. This filehandle must be
330polled for reading by some mechanism outside this module (e.g. Event or 484polled for reading by some mechanism outside this module (e.g. Event or
… …
369interactiveness when perl is not fast enough to process all requests in 523interactiveness when perl is not fast enough to process all requests in
370time. 524time.
371 525
372For interactive programs, values such as C<0.01> to C<0.1> should be fine. 526For interactive programs, values such as C<0.01> to C<0.1> should be fine.
373 527
374Example: Install an Event watcher that automatically calls 528Example: Install an EV watcher that automatically calls
375BDB::poll_cb with low priority, to ensure that other parts of the 529BDB::poll_cb with low priority, to ensure that other parts of the
376program get the CPU sometimes even under high AIO load. 530program get the CPU sometimes even under high load.
377 531
378 # try not to spend much more than 0.1s in poll_cb 532 # try not to spend much more than 0.1s in poll_cb
379 BDB::max_poll_time 0.1; 533 BDB::max_poll_time 0.1;
380 534
381 # use a low priority so other tasks have priority 535 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);
385 536
386=item BDB::poll_wait 537=item BDB::poll_wait
387 538
388If there are any outstanding requests and none of them in the result 539If there are any outstanding requests and none of them in the result
389phase, wait till the result filehandle becomes ready for reading (simply 540phase, wait till the result filehandle becomes ready for reading (simply
… …
401 552
402 BDB::poll_wait, BDB::poll_cb 553 BDB::poll_wait, BDB::poll_cb
403 554
404=item BDB::flush 555=item BDB::flush
405 556
406Wait till all outstanding AIO requests have been handled. 557Wait till all outstanding BDB requests have been handled.
407 558
408Strictly equivalent to: 559Strictly equivalent to:
409 560
410 BDB::poll_wait, BDB::poll_cb 561 BDB::poll_wait, BDB::poll_cb
411 while BDB::nreqs; 562 while BDB::nreqs;
412 563
413=back 564=back
414 565
415=head3 CONTROLLING THE NUMBER OF THREADS 566=head2 VERSION CHECKING
567
568BerkeleyDB comes in various versions, many of them have minor
569incompatibilities. This means that traditional "at least version x.x"
570checks are often not sufficient.
571
572Example: set the log_autoremove option in a way compatible with <v4.7 and
573v4.7. Note the use of & on the constants to avoid triggering a compiletime
574bug when the symbol isn't available.
575
576 $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
577 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
416 578
417=over 4 579=over 4
418 580
581=item BDB::VERSION
582
583The C<BDB::VERSION> function, when called without arguments, returns the
584Berkeley DB version as a v-string (usually with 3 components). You should
585use C<lt> and C<ge> operators exclusively to make comparisons.
586
587Example: check for at least version 4.7.
588
589 BDB::VERSION ge v4.7 or die;
590
591=item BDB::VERSION min-version
592
593Returns true if the BDB version is at least the given version (specified
594as a v-string), false otherwise.
595
596Example: check for at least version 4.5.
597
598 BDB::VERSION v4.7 or die;
599
600=item BDB::VERSION min-version, max-version
601
602Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
603and less then C<max-version>.
604
605Example: check wether version is strictly less then v4.7.
606
607 BDB::VERSION v0, v4.7
608 or die "version 4.7 is not yet supported";
609
610=back
611
612=cut
613
614sub VERSION {
615 # I was dumb enough to override the VERSION method here, so let's try
616 # to fix it up.
617
618 if ($_[0] eq __PACKAGE__) {
619 $VERSION
620 } else {
621 if (@_ > 0) {
622 return undef if VERSION_v lt $_[0];
623 if (@_ > 1) {
624 return undef if VERSION_v ge $_[1];
625 }
626 }
627
628 VERSION_v
629 }
630}
631
632=head2 CONTROLLING THE NUMBER OF THREADS
633
634=over 4
635
419=item BDB::min_parallel $nthreads 636=item BDB::min_parallel $nthreads
420 637
421Set the minimum number of AIO threads to C<$nthreads>. The current 638Set the minimum number of BDB threads to C<$nthreads>. The current
422default is C<8>, which means eight asynchronous operations can execute 639default is C<8>, which means eight asynchronous operations can execute
423concurrently at any one time (the number of outstanding requests, 640concurrently at any one time (the number of outstanding requests,
424however, is unlimited). 641however, is unlimited).
425 642
426BDB starts threads only on demand, when an AIO request is queued and 643BDB 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 644no 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 645create 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. 646is in the cache and could have been processed faster by a single thread.
430 647
431It is recommended to keep the number of threads relatively low, as some 648It 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 653Under most circumstances you don't need to call this function, as the
437module selects a default that is suitable for low to moderate load. 654module selects a default that is suitable for low to moderate load.
438 655
439=item BDB::max_parallel $nthreads 656=item BDB::max_parallel $nthreads
440 657
441Sets the maximum number of AIO threads to C<$nthreads>. If more than the 658Sets the maximum number of BDB threads to C<$nthreads>. If more than the
442specified number of threads are currently running, this function kills 659specified number of threads are currently running, this function kills
443them. This function blocks until the limit is reached. 660them. This function blocks until the limit is reached.
444 661
445While C<$nthreads> are zero, aio requests get queued but not executed 662While C<$nthreads> are zero, aio requests get queued but not executed
446until the number of threads has been increased again. 663until the number of threads has been increased again.
… …
481 698
482You can still queue as many requests as you want. Therefore, 699You can still queue as many requests as you want. Therefore,
483C<max_oustsanding> is mainly useful in simple scripts (with low values) or 700C<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). 701as a stop gap to shield against fatal memory overflow (with large values).
485 702
486=item BDB::set_sync_prepare $cb 703=item $old_cb = BDB::set_sync_prepare $cb
487 704
488Sets a callback that is called whenever a request is created without an 705Sets a callback that is called whenever a request is created without an
489explicit callback. It has to return two code references. The first is used 706explicit callback. It has to return two code references. The first is used
490as the request callback, and the second is called to wait until the first 707as the request callback (it should save the return status), and the second
491callback has been called. The default implementation works like this: 708is called to wait until the first callback has been called (it must set
709C<$!> to the return status).
710
711This mechanism can be used to include BDB into other event mechanisms,
712such as L<Coro::BDB>.
713
714To allow other, callback-based, events to be executed while callback-less
715ones are run, you could use this sync prepare function:
492 716
493 sub { 717 sub {
494 my $status; 718 my $status;
495 ( 719 (
496 sub { $status = $! }, 720 sub { $status = $! },
497 sub { BDB::poll while !defined $status; $! = $status }, 721 sub { BDB::poll while !defined $status; $! = $status },
498 ) 722 )
499 } 723 }
500 724
725It works by polling for results till the request has finished and then
726sets C<$!> to the return value. This means that if you don't use a
727callback, BDB would simply fall back to synchronous operations.
728
729By default, or if the sync prepare function is set to C<undef>, is to
730execute callback-less BDB requests in the foreground thread, setting C<$!>
731to the return value, without polling for other events.
732
501=back 733=back
502 734
503=head3 STATISTICAL INFORMATION 735=head2 STATISTICAL INFORMATION
504 736
505=over 4 737=over 4
506 738
507=item BDB::nreqs 739=item BDB::nreqs
508 740
… …
526 758
527=back 759=back
528 760
529=cut 761=cut
530 762
531set_sync_prepare { 763set_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};
543 764
544min_parallel 8; 765min_parallel 8;
545 766
546END { flush } 767END { flush }
547 768
5481; 7691;
549 770
771=head1 COMMON PITFALLS
772
773=head2 Unexpected Crashes
774
775Remember that, by default, BDB will execute requests in parallel, in
776somewhat random order. That means that it is easy to run a C<db_get>
777request on the same database as a concurrent C<db_close> request, leading
778to a crash, silent data corruption, eventually the next world war on
779terrorism.
780
781If you only ever use foreground requests (without a callback), this will
782not be an issue (unless you use threads).
783
784=head2 Unexpected Freezes or Deadlocks
785
786Remember that, by default, BDB will execute requests in parallel, which
787easily leads to deadlocks (even concurrent put's on the same database can
788deadlock).
789
790You either need to run deadlock detection (and handle the resulting
791errors), or make sure only one process ever updates the database, ine one
792thread, e.g. by using only foreground requests (without a callback).
793
550=head2 FORK BEHAVIOUR 794=head1 FORK BEHAVIOUR
551 795
552This module should do "the right thing" when the process using it forks: 796This module should do "the right thing" when the process using it forks:
553 797
554Before the fork, IO::AIO enters a quiescent state where no requests 798Before the fork, BDB enters a quiescent state where no requests
555can be added in other threads and no results will be processed. After 799can be added in other threads and no results will be processed. After
556the fork the parent simply leaves the quiescent state and continues 800the fork the parent simply leaves the quiescent state and continues
557request/result processing, while the child frees the request/result queue 801request/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 802(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 803parent). Threads will be started on demand until the limit set in the
560parent process has been reached again. 804parent process has been reached again.
561 805
562In short: the parent will, after a short pause, continue as if fork had 806In 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 807not been called, while the child will act as if BDB has not been used
564yet. 808yet.
565 809
810Win32 note: there is no fork on win32, and perls emulation of it is too
811broken to be supported, so do not use BDB in a windows pseudo-fork, better
812yet, switch to a more capable platform.
813
566=head2 MEMORY USAGE 814=head1 MEMORY USAGE
567 815
568Per-request usage: 816Per-request usage:
569 817
570Each aio request uses - depending on your architecture - around 100-200 818Each aio request uses - depending on your architecture - around 100-200
571bytes of memory. In addition, stat requests need a stat buffer (possibly 819bytes of memory. In addition, stat requests need a stat buffer (possibly
… …
580 828
581In the execution phase, some aio requests require more memory for 829In the execution phase, some aio requests require more memory for
582temporary buffers, and each thread requires a stack and other data 830temporary buffers, and each thread requires a stack and other data
583structures (usually around 16k-128k, depending on the OS). 831structures (usually around 16k-128k, depending on the OS).
584 832
833=head1 WIN32 FILENAMES/DATABASE NAME MESS
834
835Perl on Win32 supports only ASCII filenames (the reason is that it abuses
836an internal flag to store wether a filename is Unicode or ANSI, but that
837flag is used for somethign else in the perl core, so there is no way to
838detect wether a filename is ANSI or Unicode-encoded). The BDB module
839tries to work around this issue by assuming that the filename is an ANSI
840filename and BDB was built for unicode support.
841
585=head1 KNOWN BUGS 842=head1 KNOWN BUGS
586 843
587Known bugs will be fixed in the next release. 844Known bugs will be fixed in the next release, except:
845
846 If you use a transaction in any request, and the request returns
847 with an operating system error or DB_LOCK_NOTGRANTED, the internal
848 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
849 above.
588 850
589=head1 SEE ALSO 851=head1 SEE ALSO
590 852
591L<Coro::AIO>. 853L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
854syntax), L<IO::AIO> (nice to have).
592 855
593=head1 AUTHOR 856=head1 AUTHOR
594 857
595 Marc Lehmann <schmorp@schmorp.de> 858 Marc Lehmann <schmorp@schmorp.de>
596 http://home.schmorp.de/ 859 http://home.schmorp.de/

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