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Revision 1.7 by root, Sun Mar 30 06:29:07 2008 UTC vs.
Revision 1.16 by root, Wed Aug 5 11:52:34 2009 UTC

… …
25 db_sync $db; 25 db_sync $db;
26 26
27 # when you also use Coro, management is easy: 27 # when you also use Coro, management is easy:
28 use Coro::BDB; 28 use Coro::BDB;
29 29
30 # automatic result processing with AnyEvent: 30 # automatic event loop integration with AnyEvent:
31 our $FH; open $FH, "<&=" . BDB::poll_fileno; 31 use AnyEvent::BDB;
32 our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
33 32
34 # automatic result processing with EV: 33 # automatic result processing with EV:
35 my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb; 34 my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
36 35
37 # with Glib: 36 # with Glib:
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87 Request has reached the end of its lifetime and holds no resources 86 Request has reached the end of its lifetime and holds no resources
88 anymore (except possibly for the Perl object, but its connection to 87 anymore (except possibly for the Perl object, but its connection to
89 the actual aio request is severed and calling its methods will 88 the actual aio request is severed and calling its methods will
90 either do nothing or result in a runtime error). 89 either do nothing or result in a runtime error).
91 90
92 FILENAMES/DATABASE NAMES
93 The BDB expects "binary" filenames (octet strings) for pathnames on
94 POSIX systems, and "unicode" filenames (strings with characters
95 potentially >255) on Win32 (expecting a Unicode win32 build - win32 is a
96 total mess).
97
98 BERKELEYDB FUNCTIONS 91BERKELEYDB FUNCTIONS
99 All of these are functions. The create functions simply return a new 92 All of these are functions. The create functions simply return a new
100 object and never block. All the remaining functions take an optional 93 object and never block. All the remaining functions take an optional
101 callback as last argument. If it is missing, then the function will be 94 callback as last argument. If it is missing, then the function will be
102 executed synchronously. In both cases, $! will reflect the return value 95 executed synchronously. In both cases, $! will reflect the return value
103 of the function. 96 of the function.
… …
105 BDB functions that cannot block (mostly functions that manipulate 98 BDB functions that cannot block (mostly functions that manipulate
106 settings) are method calls on the relevant objects, so the rule of thumb 99 settings) are method calls on the relevant objects, so the rule of thumb
107 is: if it's a method, it's not blocking, if it's a function, it takes a 100 is: if it's a method, it's not blocking, if it's a function, it takes a
108 callback as last argument. 101 callback as last argument.
109 102
110 In the following, $int signifies an integer return value, "octetstring" 103 In the following, $int signifies an integer return value, "bdb_filename"
111 is a "binary string" (i.e. a perl string with no character indices 104 is a "filename" (octets on unix, madness on windows), "U32" is an
112 >255), "U32" is an unsigned 32 bit integer, "int" is some integer, "NV" 105 unsigned 32 bit integer, "int" is some integer, "NV" is a floating point
113 is a floating point value. 106 value.
114 107
115 The "SV *" types are generic perl scalars (for input and output of data 108 Most "SV *" types are generic perl scalars (for input and output of data
116 values), and the "SV *callback" is the optional callback function to 109 values).
117 call when the request is completed.
118 110
119 The various "DB_ENV" etc. arguments are handles return by 111 The various "DB_ENV" etc. arguments are handles return by
120 "db_env_create", "db_create", "txn_begin" and so on. If they have an 112 "db_env_create", "db_create", "txn_begin" and so on. If they have an
121 appended "_ornull" this means they are optional and you can pass "undef" 113 appended "_ornull" this means they are optional and you can pass "undef"
122 for them, resulting a NULL pointer on the C level. 114 for them, resulting a NULL pointer on the C level.
123 115
116 The "SV *callback" is the optional callback function to call when the
117 request is completed. This last callback argument is special: the
118 callback is simply the last argument passed. If there are "optional"
119 arguments before the callback they can be left out. The callback itself
120 can be left out or specified as "undef", in which case the function will
121 be executed synchronously.
122
123 For example, "db_env_txn_checkpoint" usually is called with all integer
124 arguments zero. These can be left out, so all of these specify a call to
125 "DB_ENV->txn_checkpoint", to be executed asynchronously with a callback
126 to be called:
127
128 db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
129 db_env_txn_checkpoint $db_env, 0, 0, sub { };
130 db_env_txn_checkpoint $db_env, sub { };
131
132 While these all specify a call to "DB_ENV->txn_checkpoint" to be
133 executed synchronously:
134
135 db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
136 db_env_txn_checkpoint $db_env, 0, 0, 0;
137 db_env_txn_checkpoint $db_env, 0;
138
124 BDB functions 139 BDB functions
125 Functions in the BDB namespace, exported by default: 140 Functions in the BDB namespace, exported by default:
126 141
127 $env = db_env_create (U32 env_flags = 0) 142 $env = db_env_create (U32 env_flags = 0)
128 flags: RPCCLIENT 143 flags: RPCCLIENT
129 144
130 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 145 db_env_open (DB_ENV *env, bdb_filename db_home, U32 open_flags, int mode, SV *callback = 0)
131 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 146 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
132 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) 147 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = 0)
133 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 148 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = 0)
134 flags: FORCE 149 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) 150 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = 0)
136 atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST 151 atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
137 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) 152 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = 0)
138 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) 153 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = 0)
154 db_env_dbremove (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = 0)
155 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)
156 db_env_log_archive (DB_ENV *env, SV *listp, U32 flags = 0, SV *callback = 0)
139 157
140 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 158 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
141 flags: XA_CREATE 159 flags: XA_CREATE
142 160
143 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 161 db_open (DB *db, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = 0)
144 flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE 162 flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
145 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 163 db_close (DB *db, U32 flags = 0, SV *callback = 0)
146 flags: DB_NOSYNC 164 flags: DB_NOSYNC
165 db_verify (DB *db, bdb_filename file, bdb_filename database = 0, SV *dummy = 0, U32 flags = 0, SV *callback = 0)
147 db_upgrade (DB *db, octetstring file, U32 flags = 0, SV *callback = &PL_sv_undef) 166 db_upgrade (DB *db, bdb_filename file, U32 flags = 0, SV *callback = 0)
148 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) 167 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)
149 flags: FREELIST_ONLY FREE_SPACE 168 flags: FREELIST_ONLY FREE_SPACE
150 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 169 db_sync (DB *db, U32 flags = 0, SV *callback = 0)
151 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) 170 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = 0)
152 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 171 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
153 flags: APPEND NODUPDATA NOOVERWRITE 172 flags: APPEND NODUPDATA NOOVERWRITE
173 db_exists (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = 0) (v4.6)
154 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 174 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
155 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW 175 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
156 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 176 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = 0)
157 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW 177 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
158 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 178 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = 0)
159 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) 179 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = 0)
160 flags: TXN_NOSYNC TXN_SYNC 180 flags: TXN_NOSYNC TXN_SYNC
161 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 181 db_txn_abort (DB_TXN *txn, SV *callback = 0)
162 182
163 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 183 db_c_close (DBC *dbc, SV *callback = 0)
164 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) 184 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = 0)
165 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 185 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
166 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA 186 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
167 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 187 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
168 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 188 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
169 db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 189 db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = 0)
170 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef) 190 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = 0)
171 191
172 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 192 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = 0)
173 flags: CREATE EXCL 193 flags: CREATE EXCL
174 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 194 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = 0)
175 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) 195 db_sequence_get (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, int delta, SV *seq_value, U32 flags = DB_TXN_NOSYNC, SV *callback = 0)
176 flags: TXN_NOSYNC 196 flags: TXN_NOSYNC
177 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 197 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = 0)
178 flags: TXN_NOSYNC 198 flags: TXN_NOSYNC
179 199
180 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) 200 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = 0)
181 This is not actually a Berkeley DB function but a BDB module extension. 201 This is not actually a Berkeley DB function but a BDB module extension.
182 The background for this exytension is: It is very annoying to have to 202 The background for this exytension is: It is very annoying to have to
183 check every single BDB function for error returns and provide a codepath 203 check every single BDB function for error returns and provide a codepath
184 out of your transaction. While the BDB module still makes this possible, 204 out of your transaction. While the BDB module still makes this possible,
185 it contains the following extensions: 205 it contains the following extensions:
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210 230
211 You can use the "$txn->failed" method to check wether a transaction has 231 You can use the "$txn->failed" method to check wether a transaction has
212 failed in this way and abort further processing (excluding 232 failed in this way and abort further processing (excluding
213 "db_txn_finish"). 233 "db_txn_finish").
214 234
215 DB_ENV/database environment methods 235 DB_ENV/database environment methods
216 Methods available on DB_ENV/$env handles: 236 Methods available on DB_ENV/$env handles:
217 237
218 DESTROY (DB_ENV_ornull *env) 238 DESTROY (DB_ENV_ornull *env)
219 CODE: 239 CODE:
220 if (env) 240 if (env)
… …
223 $int = $env->set_data_dir (const char *dir) 243 $int = $env->set_data_dir (const char *dir)
224 $int = $env->set_tmp_dir (const char *dir) 244 $int = $env->set_tmp_dir (const char *dir)
225 $int = $env->set_lg_dir (const char *dir) 245 $int = $env->set_lg_dir (const char *dir)
226 $int = $env->set_shm_key (long shm_key) 246 $int = $env->set_shm_key (long shm_key)
227 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 247 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
228 $int = $env->set_flags (U32 flags, int onoff) 248 $int = $env->set_flags (U32 flags, int onoff = 1)
249 $int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
250 $int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
229 $env->set_errfile (FILE *errfile = 0) 251 $env->set_errfile (FILE *errfile = 0)
230 $env->set_msgfile (FILE *msgfile = 0) 252 $env->set_msgfile (FILE *msgfile = 0)
231 $int = $env->set_verbose (U32 which, int onoff = 1) 253 $int = $env->set_verbose (U32 which, int onoff = 1)
232 $int = $env->set_encrypt (const char *password, U32 flags = 0) 254 $int = $env->set_encrypt (const char *password, U32 flags = 0)
233 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) 255 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
… …
245 $int = $env->mutex_set_max (U32 max) 267 $int = $env->mutex_set_max (U32 max)
246 $int = $env->mutex_set_align (U32 align) 268 $int = $env->mutex_set_align (U32 align)
247 269
248 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 270 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
249 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC 271 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
272 $txn = $env->cdsgroup_begin; (v4.5)
250 273
251 Example: 274 Example:
252 use AnyEvent; 275 use AnyEvent;
253 use BDB; 276 use BDB;
254 277
… …
266 BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE, 289 BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE,
267 0600; 290 0600;
268 291
269 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 292 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
270 293
271 DB/database methods 294 DB/database methods
272 Methods available on DB/$db handles: 295 Methods available on DB/$db handles:
273 296
274 DESTROY (DB_ornull *db) 297 DESTROY (DB_ornull *db)
275 CODE: 298 CODE:
276 if (db) 299 if (db)
… …
316 339
317 db_del $db, undef, "key $_" for 1..1000; 340 db_del $db, undef, "key $_" for 1..1000;
318 341
319 db_sync $db; 342 db_sync $db;
320 343
321 DB_TXN/transaction methods 344 DB_TXN/transaction methods
322 Methods available on DB_TXN/$txn handles: 345 Methods available on DB_TXN/$txn handles:
323 346
324 DESTROY (DB_TXN_ornull *txn) 347 DESTROY (DB_TXN_ornull *txn)
325 CODE: 348 CODE:
326 if (txn) 349 if (txn)
… …
330 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT 353 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
331 354
332 $bool = $txn->failed 355 $bool = $txn->failed
333 # see db_txn_finish documentation, above 356 # see db_txn_finish documentation, above
334 357
335 DBC/cursor methods 358 DBC/cursor methods
336 Methods available on DBC/$dbc handles: 359 Methods available on DBC/$dbc handles:
337 360
338 DESTROY (DBC_ornull *dbc) 361 DESTROY (DBC_ornull *dbc)
339 CODE: 362 CODE:
340 if (dbc) 363 if (dbc)
341 dbc->c_close (dbc); 364 dbc->c_close (dbc);
342 365
343 $int = $cursor->set_priority ($priority = PRIORITY_*) 366 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
344 367
345 Example: 368 Example:
346 my $c = $db->cursor; 369 my $c = $db->cursor;
347 370
348 for (;;) { 371 for (;;) {
… …
351 last if $!; 374 last if $!;
352 } 375 }
353 376
354 db_c_close $c; 377 db_c_close $c;
355 378
356 DB_SEQUENCE/sequence methods 379 DB_SEQUENCE/sequence methods
357 Methods available on DB_SEQUENCE/$seq handles: 380 Methods available on DB_SEQUENCE/$seq handles:
358 381
359 DESTROY (DB_SEQUENCE_ornull *seq) 382 DESTROY (DB_SEQUENCE_ornull *seq)
360 CODE: 383 CODE:
361 if (seq) 384 if (seq)
… …
367 flags: SEQ_DEC SEQ_INC SEQ_WRAP 390 flags: SEQ_DEC SEQ_INC SEQ_WRAP
368 $int = $seq->set_range (db_seq_t min, db_seq_t max) 391 $int = $seq->set_range (db_seq_t min, db_seq_t max)
369 392
370 Example: 393 Example:
371 my $seq = $db->sequence; 394 my $seq = $db->sequence;
372 395
373 db_sequence_open $seq, undef, "seq", BDB::CREATE; 396 db_sequence_open $seq, undef, "seq", BDB::CREATE;
374 db_sequence_get $seq, undef, 1, my $value; 397 db_sequence_get $seq, undef, 1, my $value;
375 398
376 SUPPORT FUNCTIONS 399SUPPORT FUNCTIONS
377 EVENT PROCESSING AND EVENT LOOP INTEGRATION 400 EVENT PROCESSING AND EVENT LOOP INTEGRATION
378 $msg = BDB::strerror [$errno] 401 $msg = BDB::strerror [$errno]
379 Returns the string corresponding to the given errno value. If no 402 Returns the string corresponding to the given errno value. If no
380 argument is given, use $!. 403 argument is given, use $!.
381 404
382 Note that the BDB module also patches the $! variable directly, so 405 Note that the BDB module also patches the $! variable directly, so
… …
459 Strictly equivalent to: 482 Strictly equivalent to:
460 483
461 BDB::poll_wait, BDB::poll_cb 484 BDB::poll_wait, BDB::poll_cb
462 while BDB::nreqs; 485 while BDB::nreqs;
463 486
487 VERSION CHECKING
488 BerkeleyDB comes in various versions, many of them have minor
489 incompatibilities. This means that traditional "at least version x.x"
490 checks are often not sufficient.
491
492 Example: set the log_autoremove option in a way compatible with <v4.7
493 and v4.7. Note the use of & on the constants to avoid triggering a
494 compiletime bug when the symbol isn't available.
495
496 $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
497 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
498
499 BDB::VERSION
500 The "BDB::VERSION" function, when called without arguments, returns
501 the Berkeley DB version as a v-string (usually with 3 components).
502 You should use "lt" and "ge" operators exclusively to make
503 comparisons.
504
505 Example: check for at least version 4.7.
506
507 BDB::VERSION ge v4.7 or die;
508
509 BDB::VERSION min-version
510 Returns true if the BDB version is at least the given version
511 (specified as a v-string), false otherwise.
512
513 Example: check for at least version 4.5.
514
515 BDB::VERSION v4.7 or die;
516
517 BDB::VERSION min-version, max-version
518 Returns true of the BDB version is at least version "min-version"
519 (specify "undef" or "v0" for any minimum version) and less then
520 "max-version".
521
522 Example: check wether version is strictly less then v4.7.
523
524 BDB::VERSION v0, v4.7
525 or die "version 4.7 is not yet supported";
526
464 CONTROLLING THE NUMBER OF THREADS 527 CONTROLLING THE NUMBER OF THREADS
465 BDB::min_parallel $nthreads 528 BDB::min_parallel $nthreads
466 Set the minimum number of BDB threads to $nthreads. The current 529 Set the minimum number of BDB threads to $nthreads. The current
467 default is 8, which means eight asynchronous operations can execute 530 default is 8, which means eight asynchronous operations can execute
468 concurrently at any one time (the number of outstanding requests, 531 concurrently at any one time (the number of outstanding requests,
469 however, is unlimited). 532 however, is unlimited).
… …
528 You can still queue as many requests as you want. Therefore, 591 You can still queue as many requests as you want. Therefore,
529 "max_oustsanding" is mainly useful in simple scripts (with low 592 "max_oustsanding" is mainly useful in simple scripts (with low
530 values) or as a stop gap to shield against fatal memory overflow 593 values) or as a stop gap to shield against fatal memory overflow
531 (with large values). 594 (with large values).
532 595
533 BDB::set_sync_prepare $cb 596 $old_cb = BDB::set_sync_prepare $cb
534 Sets a callback that is called whenever a request is created without 597 Sets a callback that is called whenever a request is created without
535 an explicit callback. It has to return two code references. The 598 an explicit callback. It has to return two code references. The
536 first is used as the request callback, and the second is called to 599 first is used as the request callback (it should save the return
537 wait until the first callback has been called. The default 600 status), and the second is called to wait until the first callback
538 implementation works like this: 601 has been called (it must set $! to the return status).
602
603 This mechanism can be used to include BDB into other event
604 mechanisms, such as Coro::BDB.
605
606 To allow other, callback-based, events to be executed while
607 callback-less ones are run, you could use this sync prepare
608 function:
539 609
540 sub { 610 sub {
541 my $status; 611 my $status;
542 ( 612 (
543 sub { $status = $! }, 613 sub { $status = $! },
544 sub { BDB::poll while !defined $status; $! = $status }, 614 sub { BDB::poll while !defined $status; $! = $status },
545 ) 615 )
546 } 616 }
547 617
618 It works by polling for results till the request has finished and
619 then sets $! to the return value. This means that if you don't use a
620 callback, BDB would simply fall back to synchronous operations.
621
622 By default, or if the sync prepare function is set to "undef", is to
623 execute callback-less BDB requests in the foreground thread, setting
624 $! to the return value, without polling for other events.
625
548 STATISTICAL INFORMATION 626 STATISTICAL INFORMATION
549 BDB::nreqs 627 BDB::nreqs
550 Returns the number of requests currently in the ready, execute or 628 Returns the number of requests currently in the ready, execute or
551 pending states (i.e. for which their callback has not been invoked 629 pending states (i.e. for which their callback has not been invoked
552 yet). 630 yet).
553 631
… …
562 640
563 BDB::npending 641 BDB::npending
564 Returns the number of requests currently in the pending state 642 Returns the number of requests currently in the pending state
565 (executed, but not yet processed by poll_cb). 643 (executed, but not yet processed by poll_cb).
566 644
645COMMON PITFALLS
646 Unexpected Crashes
647 Remember that, by default, BDB will execute requests in parallel, in
648 somewhat random order. That means that it is easy to run a "db_get"
649 request on thesa me database as a concurrent "db_close" request, leading
650 to a crash, silent data corruption, eventually the next world war on
651 terrorism.
652
653 If you only ever use foreground requests (without a callback), this will
654 not be an issue.
655
656 Unexpected Freezes or Deadlocks
657 Remember that, by default, BDB will execute requests in parallel, which
658 easily leads to deadlocks (even concurrent put's on the same database
659 can deadlock).
660
661 You either need to run deadlock detection (and handle the resulting
662 errors), or make sure only one process ever updates the database, ine
663 one thread, e.g. by using only foreground requests (without a callback).
664
567 FORK BEHAVIOUR 665FORK BEHAVIOUR
568 This module should do "the right thing" when the process using it forks: 666 This module should do "the right thing" when the process using it forks:
569 667
570 Before the fork, BDB enters a quiescent state where no requests can be 668 Before the fork, BDB enters a quiescent state where no requests can be
571 added in other threads and no results will be processed. After the fork 669 added in other threads and no results will be processed. After the fork
572 the parent simply leaves the quiescent state and continues 670 the parent simply leaves the quiescent state and continues
… …
581 679
582 Win32 note: there is no fork on win32, and perls emulation of it is too 680 Win32 note: there is no fork on win32, and perls emulation of it is too
583 broken to be supported, so do not use BDB in a windows pseudo-fork, 681 broken to be supported, so do not use BDB in a windows pseudo-fork,
584 better yet, switch to a more capable platform. 682 better yet, switch to a more capable platform.
585 683
586 MEMORY USAGE 684MEMORY USAGE
587 Per-request usage: 685 Per-request usage:
588 686
589 Each aio request uses - depending on your architecture - around 100-200 687 Each aio request uses - depending on your architecture - around 100-200
590 bytes of memory. In addition, stat requests need a stat buffer (possibly 688 bytes of memory. In addition, stat requests need a stat buffer (possibly
591 a few hundred bytes), readdir requires a result buffer and so on. Perl 689 a few hundred bytes), readdir requires a result buffer and so on. Perl
… …
599 697
600 In the execution phase, some aio requests require more memory for 698 In the execution phase, some aio requests require more memory for
601 temporary buffers, and each thread requires a stack and other data 699 temporary buffers, and each thread requires a stack and other data
602 structures (usually around 16k-128k, depending on the OS). 700 structures (usually around 16k-128k, depending on the OS).
603 701
702WIN32 FILENAMES/DATABASE NAME MESS
703 Perl on Win32 supports only ASCII filenames (the reason is that it
704 abuses an internal flag to store wether a filename is Unicode or ANSI,
705 but that flag is used for somethign else in the perl core, so there is
706 no way to detect wether a filename is ANSI or Unicode-encoded). The BDB
707 module tries to work around this issue by assuming that the filename is
708 an ANSI filename and BDB was built for unicode support.
709
604KNOWN BUGS 710KNOWN BUGS
605 Known bugs will be fixed in the next release, except: 711 Known bugs will be fixed in the next release, except:
606 712
607 If you use a transaction in any request, and the request returns 713 If you use a transaction in any request, and the request returns
608 with an operating system error or DB_LOCK_NOTGRANTED, the internal 714 with an operating system error or DB_LOCK_NOTGRANTED, the internal
609 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, 715 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
610 above. 716 above.
611 717
612SEE ALSO 718SEE ALSO
613 Coro::BDB, IO::AIO. 719 AnyEvent::BDB (event loop integration), Coro::BDB (more natural syntax),
720 IO::AIO (nice to have).
614 721
615AUTHOR 722AUTHOR
616 Marc Lehmann <schmorp@schmorp.de> 723 Marc Lehmann <schmorp@schmorp.de>
617 http://home.schmorp.de/ 724 http://home.schmorp.de/
618 725

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