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Revision 1.7 by root, Sun Mar 30 06:29:07 2008 UTC vs.
Revision 1.18 by root, Thu Jan 18 16:45:27 2018 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)
157 db_env_lsn_reset (DB_ENV *env, bdb_filename db, U32 flags = 0, SV *callback = 0)
158 db_env_fileid_reset (DB_ENV *env, bdb_filename db, U32 flags = 0, SV *callback = 0)
139 159
140 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 160 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
141 flags: XA_CREATE 161 flags: XA_CREATE
142 162
143 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 163 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 164 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) 165 db_close (DB *db, U32 flags = 0, SV *callback = 0)
146 flags: DB_NOSYNC 166 flags: DB_NOSYNC
167 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) 168 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) 169 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 170 flags: FREELIST_ONLY FREE_SPACE
150 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 171 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) 172 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) 173 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
153 flags: APPEND NODUPDATA NOOVERWRITE 174 flags: APPEND NODUPDATA NOOVERWRITE
175 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) 176 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 177 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) 178 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 179 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) 180 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) 181 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = 0)
160 flags: TXN_NOSYNC TXN_SYNC 182 flags: TXN_NOSYNC TXN_SYNC
161 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 183 db_txn_abort (DB_TXN *txn, SV *callback = 0)
162 184
163 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 185 db_c_close (DBC *dbc, SV *callback = 0)
164 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) 186 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) 187 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
166 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA 188 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) 189 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 190 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) 191 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) 192 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = 0)
171 193
172 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 194 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = 0)
173 flags: CREATE EXCL 195 flags: CREATE EXCL
174 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 196 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) 197 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 198 flags: TXN_NOSYNC
177 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 199 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = 0)
178 flags: TXN_NOSYNC 200 flags: TXN_NOSYNC
179 201
180 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) 202 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. 203 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 204 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 205 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, 206 out of your transaction. While the BDB module still makes this possible,
185 it contains the following extensions: 207 it contains the following extensions:
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210 232
211 You can use the "$txn->failed" method to check wether a transaction has 233 You can use the "$txn->failed" method to check wether a transaction has
212 failed in this way and abort further processing (excluding 234 failed in this way and abort further processing (excluding
213 "db_txn_finish"). 235 "db_txn_finish").
214 236
215 DB_ENV/database environment methods 237 DB_ENV/database environment methods
216 Methods available on DB_ENV/$env handles: 238 Methods available on DB_ENV/$env handles:
217 239
218 DESTROY (DB_ENV_ornull *env) 240 DESTROY (DB_ENV_ornull *env)
219 CODE: 241 CODE:
220 if (env) 242 if (env)
… …
223 $int = $env->set_data_dir (const char *dir) 245 $int = $env->set_data_dir (const char *dir)
224 $int = $env->set_tmp_dir (const char *dir) 246 $int = $env->set_tmp_dir (const char *dir)
225 $int = $env->set_lg_dir (const char *dir) 247 $int = $env->set_lg_dir (const char *dir)
226 $int = $env->set_shm_key (long shm_key) 248 $int = $env->set_shm_key (long shm_key)
227 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 249 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
228 $int = $env->set_flags (U32 flags, int onoff) 250 $int = $env->set_flags (U32 flags, int onoff = 1)
251 $int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
252 $int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
229 $env->set_errfile (FILE *errfile = 0) 253 $env->set_errfile (FILE *errfile = 0)
230 $env->set_msgfile (FILE *msgfile = 0) 254 $env->set_msgfile (FILE *msgfile = 0)
231 $int = $env->set_verbose (U32 which, int onoff = 1) 255 $int = $env->set_verbose (U32 which, int onoff = 1)
232 $int = $env->set_encrypt (const char *password, U32 flags = 0) 256 $int = $env->set_encrypt (const char *password, U32 flags = 0)
233 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) 257 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
… …
245 $int = $env->mutex_set_max (U32 max) 269 $int = $env->mutex_set_max (U32 max)
246 $int = $env->mutex_set_align (U32 align) 270 $int = $env->mutex_set_align (U32 align)
247 271
248 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 272 $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 273 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
274 $txn = $env->cdsgroup_begin; (v4.5)
250 275
251 Example: 276 Example:
252 use AnyEvent; 277 use AnyEvent;
253 use BDB; 278 use BDB;
254 279
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266 BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE, 291 BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE,
267 0600; 292 0600;
268 293
269 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 294 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
270 295
271 DB/database methods 296 DB/database methods
272 Methods available on DB/$db handles: 297 Methods available on DB/$db handles:
273 298
274 DESTROY (DB_ornull *db) 299 DESTROY (DB_ornull *db)
275 CODE: 300 CODE:
276 if (db) 301 if (db)
… …
316 341
317 db_del $db, undef, "key $_" for 1..1000; 342 db_del $db, undef, "key $_" for 1..1000;
318 343
319 db_sync $db; 344 db_sync $db;
320 345
321 DB_TXN/transaction methods 346 DB_TXN/transaction methods
322 Methods available on DB_TXN/$txn handles: 347 Methods available on DB_TXN/$txn handles:
323 348
324 DESTROY (DB_TXN_ornull *txn) 349 DESTROY (DB_TXN_ornull *txn)
325 CODE: 350 CODE:
326 if (txn) 351 if (txn)
… …
330 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT 355 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
331 356
332 $bool = $txn->failed 357 $bool = $txn->failed
333 # see db_txn_finish documentation, above 358 # see db_txn_finish documentation, above
334 359
335 DBC/cursor methods 360 DBC/cursor methods
336 Methods available on DBC/$dbc handles: 361 Methods available on DBC/$dbc handles:
337 362
338 DESTROY (DBC_ornull *dbc) 363 DESTROY (DBC_ornull *dbc)
339 CODE: 364 CODE:
340 if (dbc) 365 if (dbc)
341 dbc->c_close (dbc); 366 dbc->c_close (dbc);
342 367
343 $int = $cursor->set_priority ($priority = PRIORITY_*) 368 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
344 369
345 Example: 370 Example:
346 my $c = $db->cursor; 371 my $c = $db->cursor;
347 372
348 for (;;) { 373 for (;;) {
… …
351 last if $!; 376 last if $!;
352 } 377 }
353 378
354 db_c_close $c; 379 db_c_close $c;
355 380
356 DB_SEQUENCE/sequence methods 381 DB_SEQUENCE/sequence methods
357 Methods available on DB_SEQUENCE/$seq handles: 382 Methods available on DB_SEQUENCE/$seq handles:
358 383
359 DESTROY (DB_SEQUENCE_ornull *seq) 384 DESTROY (DB_SEQUENCE_ornull *seq)
360 CODE: 385 CODE:
361 if (seq) 386 if (seq)
… …
367 flags: SEQ_DEC SEQ_INC SEQ_WRAP 392 flags: SEQ_DEC SEQ_INC SEQ_WRAP
368 $int = $seq->set_range (db_seq_t min, db_seq_t max) 393 $int = $seq->set_range (db_seq_t min, db_seq_t max)
369 394
370 Example: 395 Example:
371 my $seq = $db->sequence; 396 my $seq = $db->sequence;
372 397
373 db_sequence_open $seq, undef, "seq", BDB::CREATE; 398 db_sequence_open $seq, undef, "seq", BDB::CREATE;
374 db_sequence_get $seq, undef, 1, my $value; 399 db_sequence_get $seq, undef, 1, my $value;
375 400
376 SUPPORT FUNCTIONS 401SUPPORT FUNCTIONS
377 EVENT PROCESSING AND EVENT LOOP INTEGRATION 402 EVENT PROCESSING AND EVENT LOOP INTEGRATION
378 $msg = BDB::strerror [$errno] 403 $msg = BDB::strerror [$errno]
379 Returns the string corresponding to the given errno value. If no 404 Returns the string corresponding to the given errno value. If no
380 argument is given, use $!. 405 argument is given, use $!.
381 406
382 Note that the BDB module also patches the $! variable directly, so 407 Note that the BDB module also patches the $! variable directly, so
… …
459 Strictly equivalent to: 484 Strictly equivalent to:
460 485
461 BDB::poll_wait, BDB::poll_cb 486 BDB::poll_wait, BDB::poll_cb
462 while BDB::nreqs; 487 while BDB::nreqs;
463 488
489 VERSION CHECKING
490 BerkeleyDB comes in various versions, many of them have minor
491 incompatibilities. This means that traditional "at least version x.x"
492 checks are often not sufficient.
493
494 Example: set the log_autoremove option in a way compatible with <v4.7
495 and v4.7. Note the use of & on the constants to avoid triggering a
496 compiletime bug when the symbol isn't available.
497
498 $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
499 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
500
501 BDB::VERSION
502 The "BDB::VERSION" function, when called without arguments, returns
503 the Berkeley DB version as a v-string (usually with 3 components).
504 You should use "lt" and "ge" operators exclusively to make
505 comparisons.
506
507 Example: check for at least version 4.7.
508
509 BDB::VERSION ge v4.7 or die;
510
511 BDB::VERSION min-version
512 Returns true if the BDB version is at least the given version
513 (specified as a v-string), false otherwise.
514
515 Example: check for at least version 4.5.
516
517 BDB::VERSION v4.7 or die;
518
519 BDB::VERSION min-version, max-version
520 Returns true of the BDB version is at least version "min-version"
521 (specify "undef" or "v0" for any minimum version) and less then
522 "max-version".
523
524 Example: check wether version is strictly less then v4.7.
525
526 BDB::VERSION v0, v4.7
527 or die "version 4.7 is not yet supported";
528
464 CONTROLLING THE NUMBER OF THREADS 529 CONTROLLING THE NUMBER OF THREADS
465 BDB::min_parallel $nthreads 530 BDB::min_parallel $nthreads
466 Set the minimum number of BDB threads to $nthreads. The current 531 Set the minimum number of BDB threads to $nthreads. The current
467 default is 8, which means eight asynchronous operations can execute 532 default is 8, which means eight asynchronous operations can execute
468 concurrently at any one time (the number of outstanding requests, 533 concurrently at any one time (the number of outstanding requests,
469 however, is unlimited). 534 however, is unlimited).
… …
528 You can still queue as many requests as you want. Therefore, 593 You can still queue as many requests as you want. Therefore,
529 "max_oustsanding" is mainly useful in simple scripts (with low 594 "max_oustsanding" is mainly useful in simple scripts (with low
530 values) or as a stop gap to shield against fatal memory overflow 595 values) or as a stop gap to shield against fatal memory overflow
531 (with large values). 596 (with large values).
532 597
533 BDB::set_sync_prepare $cb 598 $old_cb = BDB::set_sync_prepare $cb
534 Sets a callback that is called whenever a request is created without 599 Sets a callback that is called whenever a request is created without
535 an explicit callback. It has to return two code references. The 600 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 601 first is used as the request callback (it should save the return
537 wait until the first callback has been called. The default 602 status), and the second is called to wait until the first callback
538 implementation works like this: 603 has been called (it must set $! to the return status).
604
605 This mechanism can be used to include BDB into other event
606 mechanisms, such as Coro::BDB.
607
608 To allow other, callback-based, events to be executed while
609 callback-less ones are run, you could use this sync prepare
610 function:
539 611
540 sub { 612 sub {
541 my $status; 613 my $status;
542 ( 614 (
543 sub { $status = $! }, 615 sub { $status = $! },
544 sub { BDB::poll while !defined $status; $! = $status }, 616 sub { BDB::poll while !defined $status; $! = $status },
545 ) 617 )
546 } 618 }
547 619
620 It works by polling for results till the request has finished and
621 then sets $! to the return value. This means that if you don't use a
622 callback, BDB would simply fall back to synchronous operations.
623
624 By default, or if the sync prepare function is set to "undef", is to
625 execute callback-less BDB requests in the foreground thread, setting
626 $! to the return value, without polling for other events.
627
548 STATISTICAL INFORMATION 628 STATISTICAL INFORMATION
549 BDB::nreqs 629 BDB::nreqs
550 Returns the number of requests currently in the ready, execute or 630 Returns the number of requests currently in the ready, execute or
551 pending states (i.e. for which their callback has not been invoked 631 pending states (i.e. for which their callback has not been invoked
552 yet). 632 yet).
553 633
… …
562 642
563 BDB::npending 643 BDB::npending
564 Returns the number of requests currently in the pending state 644 Returns the number of requests currently in the pending state
565 (executed, but not yet processed by poll_cb). 645 (executed, but not yet processed by poll_cb).
566 646
647COMMON PITFALLS
648 Unexpected Crashes
649 Remember that, by default, BDB will execute requests in parallel, in
650 somewhat random order. That means that it is easy to run a "db_get"
651 request on the same database as a concurrent "db_close" request, leading
652 to a crash, silent data corruption, eventually the next world war on
653 terrorism.
654
655 If you only ever use foreground requests (without a callback), this will
656 not be an issue (unless you use threads).
657
658 Unexpected Freezes or Deadlocks
659 Remember that, by default, BDB will execute requests in parallel, which
660 easily leads to deadlocks (even concurrent put's on the same database
661 can deadlock).
662
663 You either need to run deadlock detection (and handle the resulting
664 errors), or make sure only one process ever updates the database, ine
665 one thread, e.g. by using only foreground requests (without a callback).
666
567 FORK BEHAVIOUR 667FORK BEHAVIOUR
568 This module should do "the right thing" when the process using it forks: 668 This module should do "the right thing" when the process using it forks:
569 669
570 Before the fork, BDB enters a quiescent state where no requests can be 670 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 671 added in other threads and no results will be processed. After the fork
572 the parent simply leaves the quiescent state and continues 672 the parent simply leaves the quiescent state and continues
… …
581 681
582 Win32 note: there is no fork on win32, and perls emulation of it is too 682 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, 683 broken to be supported, so do not use BDB in a windows pseudo-fork,
584 better yet, switch to a more capable platform. 684 better yet, switch to a more capable platform.
585 685
586 MEMORY USAGE 686MEMORY USAGE
587 Per-request usage: 687 Per-request usage:
588 688
589 Each aio request uses - depending on your architecture - around 100-200 689 Each aio request uses - depending on your architecture - around 100-200
590 bytes of memory. In addition, stat requests need a stat buffer (possibly 690 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 691 a few hundred bytes), readdir requires a result buffer and so on. Perl
… …
599 699
600 In the execution phase, some aio requests require more memory for 700 In the execution phase, some aio requests require more memory for
601 temporary buffers, and each thread requires a stack and other data 701 temporary buffers, and each thread requires a stack and other data
602 structures (usually around 16k-128k, depending on the OS). 702 structures (usually around 16k-128k, depending on the OS).
603 703
704WIN32 FILENAMES/DATABASE NAME MESS
705 Perl on Win32 supports only ASCII filenames (the reason is that it
706 abuses an internal flag to store wether a filename is Unicode or ANSI,
707 but that flag is used for somethign else in the perl core, so there is
708 no way to detect wether a filename is ANSI or Unicode-encoded). The BDB
709 module tries to work around this issue by assuming that the filename is
710 an ANSI filename and BDB was built for unicode support.
711
604KNOWN BUGS 712KNOWN BUGS
605 Known bugs will be fixed in the next release, except: 713 Known bugs will be fixed in the next release, except:
606 714
607 If you use a transaction in any request, and the request returns 715 If you use a transaction in any request, and the request returns
608 with an operating system error or DB_LOCK_NOTGRANTED, the internal 716 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>, 717 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
610 above. 718 above.
611 719
612SEE ALSO 720SEE ALSO
613 Coro::BDB, IO::AIO. 721 AnyEvent::BDB (event loop integration), Coro::BDB (more natural syntax),
722 IO::AIO (nice to have).
614 723
615AUTHOR 724AUTHOR
616 Marc Lehmann <schmorp@schmorp.de> 725 Marc Lehmann <schmorp@schmorp.de>
617 http://home.schmorp.de/ 726 http://home.schmorp.de/
618 727

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