ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/BDB/README
(Generate patch)

Comparing BDB/README (file contents):
Revision 1.5 by root, Wed Dec 12 01:20:54 2007 UTC vs.
Revision 1.15 by root, Sun Jan 11 00:56:09 2009 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 intergration 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:
… …
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)
130 157
131 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 158 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
132 flags: XA_CREATE 159 flags: XA_CREATE
133 160
134 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)
135 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
136 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 163 db_close (DB *db, U32 flags = 0, SV *callback = 0)
137 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)
138 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)
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) 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)
140 flags: FREELIST_ONLY FREE_SPACE 168 flags: FREELIST_ONLY FREE_SPACE
141 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 169 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) 170 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) 171 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
144 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)
145 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)
146 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
147 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)
148 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
149 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)
150 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)
151 flags: TXN_NOSYNC TXN_SYNC 180 flags: TXN_NOSYNC TXN_SYNC
152 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 181 db_txn_abort (DB_TXN *txn, SV *callback = 0)
153 182
154 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 183 db_c_close (DBC *dbc, SV *callback = 0)
155 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)
156 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)
157 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA 186 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) 187 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 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
160 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)
161 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)
162 191
163 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)
164 flags: CREATE EXCL 193 flags: CREATE EXCL
165 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)
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) 195 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 196 flags: TXN_NOSYNC
168 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)
169 flags: TXN_NOSYNC 198 flags: TXN_NOSYNC
170 199
171 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)
172 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.
173 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
174 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
175 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,
176 it contains the following extensions: 205 it contains the following extensions:
… …
201 230
202 You can use the "$txn->failed" method to check wether a transaction has 231 You can use the "$txn->failed" method to check wether a transaction has
203 failed in this way and abort further processing (excluding 232 failed in this way and abort further processing (excluding
204 "db_txn_finish"). 233 "db_txn_finish").
205 234
206 DB_ENV/database environment methods 235 DB_ENV/database environment methods
207 Methods available on DB_ENV/$env handles: 236 Methods available on DB_ENV/$env handles:
208 237
209 DESTROY (DB_ENV_ornull *env) 238 DESTROY (DB_ENV_ornull *env)
210 CODE: 239 CODE:
211 if (env) 240 if (env)
… …
214 $int = $env->set_data_dir (const char *dir) 243 $int = $env->set_data_dir (const char *dir)
215 $int = $env->set_tmp_dir (const char *dir) 244 $int = $env->set_tmp_dir (const char *dir)
216 $int = $env->set_lg_dir (const char *dir) 245 $int = $env->set_lg_dir (const char *dir)
217 $int = $env->set_shm_key (long shm_key) 246 $int = $env->set_shm_key (long shm_key)
218 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 247 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
219 $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)
220 $env->set_errfile (FILE *errfile = 0) 251 $env->set_errfile (FILE *errfile = 0)
221 $env->set_msgfile (FILE *msgfile = 0) 252 $env->set_msgfile (FILE *msgfile = 0)
222 $int = $env->set_verbose (U32 which, int onoff = 1) 253 $int = $env->set_verbose (U32 which, int onoff = 1)
223 $int = $env->set_encrypt (const char *password, U32 flags = 0) 254 $int = $env->set_encrypt (const char *password, U32 flags = 0)
224 $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)
… …
236 $int = $env->mutex_set_max (U32 max) 267 $int = $env->mutex_set_max (U32 max)
237 $int = $env->mutex_set_align (U32 align) 268 $int = $env->mutex_set_align (U32 align)
238 269
239 $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)
240 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)
241 273
242 Example: 274 Example:
243 use AnyEvent; 275 use AnyEvent;
244 use BDB; 276 use BDB;
245 277
… …
257 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,
258 0600; 290 0600;
259 291
260 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 292 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
261 293
262 DB/database methods 294 DB/database methods
263 Methods available on DB/$db handles: 295 Methods available on DB/$db handles:
264 296
265 DESTROY (DB_ornull *db) 297 DESTROY (DB_ornull *db)
266 CODE: 298 CODE:
267 if (db) 299 if (db)
… …
307 339
308 db_del $db, undef, "key $_" for 1..1000; 340 db_del $db, undef, "key $_" for 1..1000;
309 341
310 db_sync $db; 342 db_sync $db;
311 343
312 DB_TXN/transaction methods 344 DB_TXN/transaction methods
313 Methods available on DB_TXN/$txn handles: 345 Methods available on DB_TXN/$txn handles:
314 346
315 DESTROY (DB_TXN_ornull *txn) 347 DESTROY (DB_TXN_ornull *txn)
316 CODE: 348 CODE:
317 if (txn) 349 if (txn)
… …
321 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT 353 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
322 354
323 $bool = $txn->failed 355 $bool = $txn->failed
324 # see db_txn_finish documentation, above 356 # see db_txn_finish documentation, above
325 357
326 DBC/cursor methods 358 DBC/cursor methods
327 Methods available on DBC/$dbc handles: 359 Methods available on DBC/$dbc handles:
328 360
329 DESTROY (DBC_ornull *dbc) 361 DESTROY (DBC_ornull *dbc)
330 CODE: 362 CODE:
331 if (dbc) 363 if (dbc)
332 dbc->c_close (dbc); 364 dbc->c_close (dbc);
365
366 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
333 367
334 Example: 368 Example:
335 my $c = $db->cursor; 369 my $c = $db->cursor;
336 370
337 for (;;) { 371 for (;;) {
… …
340 last if $!; 374 last if $!;
341 } 375 }
342 376
343 db_c_close $c; 377 db_c_close $c;
344 378
345 DB_SEQUENCE/sequence methods 379 DB_SEQUENCE/sequence methods
346 Methods available on DB_SEQUENCE/$seq handles: 380 Methods available on DB_SEQUENCE/$seq handles:
347 381
348 DESTROY (DB_SEQUENCE_ornull *seq) 382 DESTROY (DB_SEQUENCE_ornull *seq)
349 CODE: 383 CODE:
350 if (seq) 384 if (seq)
… …
356 flags: SEQ_DEC SEQ_INC SEQ_WRAP 390 flags: SEQ_DEC SEQ_INC SEQ_WRAP
357 $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)
358 392
359 Example: 393 Example:
360 my $seq = $db->sequence; 394 my $seq = $db->sequence;
361 395
362 db_sequence_open $seq, undef, "seq", BDB::CREATE; 396 db_sequence_open $seq, undef, "seq", BDB::CREATE;
363 db_sequence_get $seq, undef, 1, my $value; 397 db_sequence_get $seq, undef, 1, my $value;
364 398
365 SUPPORT FUNCTIONS 399SUPPORT FUNCTIONS
366 EVENT PROCESSING AND EVENT LOOP INTEGRATION 400 EVENT PROCESSING AND EVENT LOOP INTEGRATION
367 $msg = BDB::strerror [$errno] 401 $msg = BDB::strerror [$errno]
368 Returns the string corresponding to the given errno value. If no 402 Returns the string corresponding to the given errno value. If no
369 argument is given, use $!. 403 argument is given, use $!.
404
405 Note that the BDB module also patches the $! variable directly, so
406 you should be able to get a bdb error string by simply stringifying
407 $!.
370 408
371 $fileno = BDB::poll_fileno 409 $fileno = BDB::poll_fileno
372 Return the *request result pipe file descriptor*. This filehandle 410 Return the *request result pipe file descriptor*. This filehandle
373 must be polled for reading by some mechanism outside this module 411 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 412 (e.g. Event or select, see below or the SYNOPSIS). If the pipe
… …
444 Strictly equivalent to: 482 Strictly equivalent to:
445 483
446 BDB::poll_wait, BDB::poll_cb 484 BDB::poll_wait, BDB::poll_cb
447 while BDB::nreqs; 485 while BDB::nreqs;
448 486
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
449 CONTROLLING THE NUMBER OF THREADS 527 CONTROLLING THE NUMBER OF THREADS
450 BDB::min_parallel $nthreads 528 BDB::min_parallel $nthreads
451 Set the minimum number of BDB threads to $nthreads. The current 529 Set the minimum number of BDB threads to $nthreads. The current
452 default is 8, which means eight asynchronous operations can execute 530 default is 8, which means eight asynchronous operations can execute
453 concurrently at any one time (the number of outstanding requests, 531 concurrently at any one time (the number of outstanding requests,
454 however, is unlimited). 532 however, is unlimited).
… …
513 You can still queue as many requests as you want. Therefore, 591 You can still queue as many requests as you want. Therefore,
514 "max_oustsanding" is mainly useful in simple scripts (with low 592 "max_oustsanding" is mainly useful in simple scripts (with low
515 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
516 (with large values). 594 (with large values).
517 595
518 BDB::set_sync_prepare $cb 596 $old_cb = BDB::set_sync_prepare $cb
519 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
520 an explicit callback. It has to return two code references. The 598 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 599 first is used as the request callback (it should save the return
522 wait until the first callback has been called. The default 600 status), and the second is called to wait until the first callback
523 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:
524 609
525 sub { 610 sub {
526 my $status; 611 my $status;
527 ( 612 (
528 sub { $status = $! }, 613 sub { $status = $! },
529 sub { BDB::poll while !defined $status; $! = $status }, 614 sub { BDB::poll while !defined $status; $! = $status },
530 ) 615 )
531 } 616 }
532 617
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
533 STATISTICAL INFORMATION 626 STATISTICAL INFORMATION
534 BDB::nreqs 627 BDB::nreqs
535 Returns the number of requests currently in the ready, execute or 628 Returns the number of requests currently in the ready, execute or
536 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
537 yet). 630 yet).
538 631
… …
547 640
548 BDB::npending 641 BDB::npending
549 Returns the number of requests currently in the pending state 642 Returns the number of requests currently in the pending state
550 (executed, but not yet processed by poll_cb). 643 (executed, but not yet processed by poll_cb).
551 644
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
552 FORK BEHAVIOUR 665FORK BEHAVIOUR
553 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:
554 667
555 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
556 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
557 the parent simply leaves the quiescent state and continues 670 the parent simply leaves the quiescent state and continues
… …
566 679
567 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
568 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,
569 better yet, switch to a more capable platform. 682 better yet, switch to a more capable platform.
570 683
571 MEMORY USAGE 684MEMORY USAGE
572 Per-request usage: 685 Per-request usage:
573 686
574 Each aio request uses - depending on your architecture - around 100-200 687 Each aio request uses - depending on your architecture - around 100-200
575 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
576 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
… …
584 697
585 In the execution phase, some aio requests require more memory for 698 In the execution phase, some aio requests require more memory for
586 temporary buffers, and each thread requires a stack and other data 699 temporary buffers, and each thread requires a stack and other data
587 structures (usually around 16k-128k, depending on the OS). 700 structures (usually around 16k-128k, depending on the OS).
588 701
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
589KNOWN BUGS 710KNOWN BUGS
590 Known bugs will be fixed in the next release, except: 711 Known bugs will be fixed in the next release, except:
591 712
592 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
593 with an operating system error or DB_LOCK_NOTGRANTED, the internal 714 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>, 715 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
595 above. 716 above.
596 717
597SEE ALSO 718SEE ALSO
598 Coro::BDB, IO::AIO. 719 AnyEvent::BDB (event loop integration), Coro::BDB (more natural syntax),
720 IO::AIO (nice to have).
599 721
600AUTHOR 722AUTHOR
601 Marc Lehmann <schmorp@schmorp.de> 723 Marc Lehmann <schmorp@schmorp.de>
602 http://home.schmorp.de/ 724 http://home.schmorp.de/
603 725

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines