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Revision 1.5 by root, Wed Dec 12 01:20:54 2007 UTC vs.
Revision 1.18 by root, Thu Jan 18 16:45:27 2018 UTC

… …
22 db_put $db, undef, "key", "data", 0, sub { 22 db_put $db, undef, "key", "data", 0, sub {
23 db_del $db, undef, "key"; 23 db_del $db, undef, "key";
24 }; 24 };
25 db_sync $db; 25 db_sync $db;
26 26
27 # automatic result processing with AnyEvent: 27 # when you also use Coro, management is easy:
28 our $FH; open $FH, "<&=" . BDB::poll_fileno; 28 use Coro::BDB;
29 our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb); 29
30 # automatic event loop integration with AnyEvent:
31 use AnyEvent::BDB;
30 32
31 # automatic result processing with EV: 33 # automatic result processing with EV:
32 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;
33 35
34 # with Glib: 36 # with Glib:
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84 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
85 anymore (except possibly for the Perl object, but its connection to 87 anymore (except possibly for the Perl object, but its connection to
86 the actual aio request is severed and calling its methods will 88 the actual aio request is severed and calling its methods will
87 either do nothing or result in a runtime error). 89 either do nothing or result in a runtime error).
88 90
89 BERKELEYDB FUNCTIONS 91BERKELEYDB FUNCTIONS
90 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
91 object and never block. All the remaining functions all take an optional 93 object and never block. All the remaining functions take an optional
92 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
93 executed synchronously. In both cases, $! will reflect the return value 95 executed synchronously. In both cases, $! will reflect the return value
94 of the function. 96 of the function.
95 97
96 BDB functions that cannot block (mostly functions that manipulate 98 BDB functions that cannot block (mostly functions that manipulate
97 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
98 is: if its a method, its not blocking, if its a function, it takes a 100 is: if it's a method, it's not blocking, if it's a function, it takes a
99 callback as last argument. 101 callback as last argument.
100 102
101 In the following, $int signifies an integer return value, "octetstring" 103 In the following, $int signifies an integer return value, "bdb_filename"
102 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
103 >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
104 is a floating point value. 106 value.
105 107
106 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
107 values), and the "SV *callback" is the optional callback function to 109 values).
108 call when the request is completed.
109 110
110 The various "DB_ENV" etc. arguments are handles return by 111 The various "DB_ENV" etc. arguments are handles return by
111 "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
112 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"
113 for them, resulting a NULL pointer on the C level. 114 for them, resulting a NULL pointer on the C level.
114 115
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
115 BDB functions 139 BDB functions
116 Functions in the BDB namespace, exported by default: 140 Functions in the BDB namespace, exported by default:
117 141
118 $env = db_env_create (U32 env_flags = 0) 142 $env = db_env_create (U32 env_flags = 0)
119 flags: RPCCLIENT 143 flags: RPCCLIENT
120 144
121 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)
122 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
123 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)
124 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)
125 flags: FORCE 149 flags: FORCE
126 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)
127 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
128 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)
129 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)
130 159
131 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 160 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
132 flags: XA_CREATE 161 flags: XA_CREATE
133 162
134 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)
135 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
136 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 165 db_close (DB *db, U32 flags = 0, SV *callback = 0)
137 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)
138 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)
139 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)
140 flags: FREELIST_ONLY FREE_SPACE 170 flags: FREELIST_ONLY FREE_SPACE
141 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 171 db_sync (DB *db, U32 flags = 0, SV *callback = 0)
142 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)
143 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)
144 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)
145 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)
146 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
147 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)
148 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
149 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)
150 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)
151 flags: TXN_NOSYNC TXN_SYNC 182 flags: TXN_NOSYNC TXN_SYNC
152 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 183 db_txn_abort (DB_TXN *txn, SV *callback = 0)
153 184
154 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 185 db_c_close (DBC *dbc, SV *callback = 0)
155 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)
156 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)
157 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA 188 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
158 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)
159 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
160 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)
161 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)
162 193
163 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)
164 flags: CREATE EXCL 195 flags: CREATE EXCL
165 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)
166 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)
167 flags: TXN_NOSYNC 198 flags: TXN_NOSYNC
168 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)
169 flags: TXN_NOSYNC 200 flags: TXN_NOSYNC
170 201
171 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)
172 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.
173 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
174 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
175 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,
176 it contains the following extensions: 207 it contains the following extensions:
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201 232
202 You can use the "$txn->failed" method to check wether a transaction has 233 You can use the "$txn->failed" method to check wether a transaction has
203 failed in this way and abort further processing (excluding 234 failed in this way and abort further processing (excluding
204 "db_txn_finish"). 235 "db_txn_finish").
205 236
206 DB_ENV/database environment methods 237 DB_ENV/database environment methods
207 Methods available on DB_ENV/$env handles: 238 Methods available on DB_ENV/$env handles:
208 239
209 DESTROY (DB_ENV_ornull *env) 240 DESTROY (DB_ENV_ornull *env)
210 CODE: 241 CODE:
211 if (env) 242 if (env)
… …
214 $int = $env->set_data_dir (const char *dir) 245 $int = $env->set_data_dir (const char *dir)
215 $int = $env->set_tmp_dir (const char *dir) 246 $int = $env->set_tmp_dir (const char *dir)
216 $int = $env->set_lg_dir (const char *dir) 247 $int = $env->set_lg_dir (const char *dir)
217 $int = $env->set_shm_key (long shm_key) 248 $int = $env->set_shm_key (long shm_key)
218 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 249 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
219 $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)
220 $env->set_errfile (FILE *errfile = 0) 253 $env->set_errfile (FILE *errfile = 0)
221 $env->set_msgfile (FILE *msgfile = 0) 254 $env->set_msgfile (FILE *msgfile = 0)
222 $int = $env->set_verbose (U32 which, int onoff = 1) 255 $int = $env->set_verbose (U32 which, int onoff = 1)
223 $int = $env->set_encrypt (const char *password, U32 flags = 0) 256 $int = $env->set_encrypt (const char *password, U32 flags = 0)
224 $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)
… …
236 $int = $env->mutex_set_max (U32 max) 269 $int = $env->mutex_set_max (U32 max)
237 $int = $env->mutex_set_align (U32 align) 270 $int = $env->mutex_set_align (U32 align)
238 271
239 $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)
240 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)
241 275
242 Example: 276 Example:
243 use AnyEvent; 277 use AnyEvent;
244 use BDB; 278 use BDB;
245 279
… …
257 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,
258 0600; 292 0600;
259 293
260 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 294 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
261 295
262 DB/database methods 296 DB/database methods
263 Methods available on DB/$db handles: 297 Methods available on DB/$db handles:
264 298
265 DESTROY (DB_ornull *db) 299 DESTROY (DB_ornull *db)
266 CODE: 300 CODE:
267 if (db) 301 if (db)
… …
307 341
308 db_del $db, undef, "key $_" for 1..1000; 342 db_del $db, undef, "key $_" for 1..1000;
309 343
310 db_sync $db; 344 db_sync $db;
311 345
312 DB_TXN/transaction methods 346 DB_TXN/transaction methods
313 Methods available on DB_TXN/$txn handles: 347 Methods available on DB_TXN/$txn handles:
314 348
315 DESTROY (DB_TXN_ornull *txn) 349 DESTROY (DB_TXN_ornull *txn)
316 CODE: 350 CODE:
317 if (txn) 351 if (txn)
… …
321 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT 355 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
322 356
323 $bool = $txn->failed 357 $bool = $txn->failed
324 # see db_txn_finish documentation, above 358 # see db_txn_finish documentation, above
325 359
326 DBC/cursor methods 360 DBC/cursor methods
327 Methods available on DBC/$dbc handles: 361 Methods available on DBC/$dbc handles:
328 362
329 DESTROY (DBC_ornull *dbc) 363 DESTROY (DBC_ornull *dbc)
330 CODE: 364 CODE:
331 if (dbc) 365 if (dbc)
332 dbc->c_close (dbc); 366 dbc->c_close (dbc);
367
368 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
333 369
334 Example: 370 Example:
335 my $c = $db->cursor; 371 my $c = $db->cursor;
336 372
337 for (;;) { 373 for (;;) {
… …
340 last if $!; 376 last if $!;
341 } 377 }
342 378
343 db_c_close $c; 379 db_c_close $c;
344 380
345 DB_SEQUENCE/sequence methods 381 DB_SEQUENCE/sequence methods
346 Methods available on DB_SEQUENCE/$seq handles: 382 Methods available on DB_SEQUENCE/$seq handles:
347 383
348 DESTROY (DB_SEQUENCE_ornull *seq) 384 DESTROY (DB_SEQUENCE_ornull *seq)
349 CODE: 385 CODE:
350 if (seq) 386 if (seq)
… …
360 my $seq = $db->sequence; 396 my $seq = $db->sequence;
361 397
362 db_sequence_open $seq, undef, "seq", BDB::CREATE; 398 db_sequence_open $seq, undef, "seq", BDB::CREATE;
363 db_sequence_get $seq, undef, 1, my $value; 399 db_sequence_get $seq, undef, 1, my $value;
364 400
365 SUPPORT FUNCTIONS 401SUPPORT FUNCTIONS
366 EVENT PROCESSING AND EVENT LOOP INTEGRATION 402 EVENT PROCESSING AND EVENT LOOP INTEGRATION
367 $msg = BDB::strerror [$errno] 403 $msg = BDB::strerror [$errno]
368 Returns the string corresponding to the given errno value. If no 404 Returns the string corresponding to the given errno value. If no
369 argument is given, use $!. 405 argument is given, use $!.
406
407 Note that the BDB module also patches the $! variable directly, so
408 you should be able to get a bdb error string by simply stringifying
409 $!.
370 410
371 $fileno = BDB::poll_fileno 411 $fileno = BDB::poll_fileno
372 Return the *request result pipe file descriptor*. This filehandle 412 Return the *request result pipe file descriptor*. This filehandle
373 must be polled for reading by some mechanism outside this module 413 must be polled for reading by some mechanism outside this module
374 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 414 (e.g. Event or select, see below or the SYNOPSIS). If the pipe
… …
444 Strictly equivalent to: 484 Strictly equivalent to:
445 485
446 BDB::poll_wait, BDB::poll_cb 486 BDB::poll_wait, BDB::poll_cb
447 while BDB::nreqs; 487 while BDB::nreqs;
448 488
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
449 CONTROLLING THE NUMBER OF THREADS 529 CONTROLLING THE NUMBER OF THREADS
450 BDB::min_parallel $nthreads 530 BDB::min_parallel $nthreads
451 Set the minimum number of BDB threads to $nthreads. The current 531 Set the minimum number of BDB threads to $nthreads. The current
452 default is 8, which means eight asynchronous operations can execute 532 default is 8, which means eight asynchronous operations can execute
453 concurrently at any one time (the number of outstanding requests, 533 concurrently at any one time (the number of outstanding requests,
454 however, is unlimited). 534 however, is unlimited).
… …
513 You can still queue as many requests as you want. Therefore, 593 You can still queue as many requests as you want. Therefore,
514 "max_oustsanding" is mainly useful in simple scripts (with low 594 "max_oustsanding" is mainly useful in simple scripts (with low
515 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
516 (with large values). 596 (with large values).
517 597
518 BDB::set_sync_prepare $cb 598 $old_cb = BDB::set_sync_prepare $cb
519 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
520 an explicit callback. It has to return two code references. The 600 an explicit callback. It has to return two code references. The
521 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
522 wait until the first callback has been called. The default 602 status), and the second is called to wait until the first callback
523 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:
524 611
525 sub { 612 sub {
526 my $status; 613 my $status;
527 ( 614 (
528 sub { $status = $! }, 615 sub { $status = $! },
529 sub { BDB::poll while !defined $status; $! = $status }, 616 sub { BDB::poll while !defined $status; $! = $status },
530 ) 617 )
531 } 618 }
532 619
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
533 STATISTICAL INFORMATION 628 STATISTICAL INFORMATION
534 BDB::nreqs 629 BDB::nreqs
535 Returns the number of requests currently in the ready, execute or 630 Returns the number of requests currently in the ready, execute or
536 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
537 yet). 632 yet).
538 633
… …
547 642
548 BDB::npending 643 BDB::npending
549 Returns the number of requests currently in the pending state 644 Returns the number of requests currently in the pending state
550 (executed, but not yet processed by poll_cb). 645 (executed, but not yet processed by poll_cb).
551 646
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
552 FORK BEHAVIOUR 667FORK BEHAVIOUR
553 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:
554 669
555 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
556 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
557 the parent simply leaves the quiescent state and continues 672 the parent simply leaves the quiescent state and continues
… …
566 681
567 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
568 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,
569 better yet, switch to a more capable platform. 684 better yet, switch to a more capable platform.
570 685
571 MEMORY USAGE 686MEMORY USAGE
572 Per-request usage: 687 Per-request usage:
573 688
574 Each aio request uses - depending on your architecture - around 100-200 689 Each aio request uses - depending on your architecture - around 100-200
575 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
576 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
… …
584 699
585 In the execution phase, some aio requests require more memory for 700 In the execution phase, some aio requests require more memory for
586 temporary buffers, and each thread requires a stack and other data 701 temporary buffers, and each thread requires a stack and other data
587 structures (usually around 16k-128k, depending on the OS). 702 structures (usually around 16k-128k, depending on the OS).
588 703
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
589KNOWN BUGS 712KNOWN BUGS
590 Known bugs will be fixed in the next release, except: 713 Known bugs will be fixed in the next release, except:
591 714
592 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
593 with an operating system error or DB_LOCK_NOTGRANTED, the internal 716 with an operating system error or DB_LOCK_NOTGRANTED, the internal
594 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>,
595 above. 718 above.
596 719
597SEE ALSO 720SEE ALSO
598 Coro::BDB, IO::AIO. 721 AnyEvent::BDB (event loop integration), Coro::BDB (more natural syntax),
722 IO::AIO (nice to have).
599 723
600AUTHOR 724AUTHOR
601 Marc Lehmann <schmorp@schmorp.de> 725 Marc Lehmann <schmorp@schmorp.de>
602 http://home.schmorp.de/ 726 http://home.schmorp.de/
603 727

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