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Revision 1.4 by root, Fri Dec 7 13:39:04 2007 UTC vs.
Revision 1.17 by root, Fri Apr 11 04:25:57 2014 UTC

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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 fucntion will be 94 callback as last argument. If it is missing, then the function will be
93 executed synchronously. 95 executed synchronously. In both cases, $! will reflect the return value
96 of the function.
94 97
95 BDB functions that cannot block (mostly functions that manipulate 98 BDB functions that cannot block (mostly functions that manipulate
96 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
97 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
98 callback as last argument. 101 callback as last argument.
99 102
100 In the following, $int signifies an integer return value, "octetstring" 103 In the following, $int signifies an integer return value, "bdb_filename"
101 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
102 >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
103 is a floating point value. 106 value.
104 107
105 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
106 values), and the "SV *callback" is the optional callback function to 109 values).
107 call when the request is completed.
108 110
109 The various "DB_ENV" etc. arguments are handles return by 111 The various "DB_ENV" etc. arguments are handles return by
110 "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
111 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"
112 for them, resulting a NULL pointer on the C level. 114 for them, resulting a NULL pointer on the C level.
113 115
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
114 BDB functions 139 BDB functions
115 Functions in the BDB namespace, exported by default: 140 Functions in the BDB namespace, exported by default:
116 141
117 $env = db_env_create (U32 env_flags = 0) 142 $env = db_env_create (U32 env_flags = 0)
118 flags: RPCCLIENT 143 flags: RPCCLIENT
119 144
120 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)
121 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
122 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)
123 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)
124 flags: FORCE 149 flags: FORCE
125 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)
126 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
127 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)
128 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)
129 157
130 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 158 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
131 flags: XA_CREATE 159 flags: XA_CREATE
132 160
133 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)
134 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
135 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 163 db_close (DB *db, U32 flags = 0, SV *callback = 0)
136 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)
166 db_upgrade (DB *db, bdb_filename file, U32 flags = 0, SV *callback = 0)
137 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)
138 flags: FREELIST_ONLY FREE_SPACE 168 flags: FREELIST_ONLY FREE_SPACE
139 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 169 db_sync (DB *db, U32 flags = 0, SV *callback = 0)
140 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)
141 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)
142 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)
143 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)
144 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
145 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)
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_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)
148 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)
149 flags: TXN_NOSYNC TXN_SYNC 180 flags: TXN_NOSYNC TXN_SYNC
150 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 181 db_txn_abort (DB_TXN *txn, SV *callback = 0)
151 182
152 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 183 db_c_close (DBC *dbc, SV *callback = 0)
153 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)
154 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)
155 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA 186 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
156 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)
157 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
158 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)
159 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)
160 191
161 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)
162 flags: CREATE EXCL 193 flags: CREATE EXCL
163 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)
164 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)
165 flags: TXN_NOSYNC 196 flags: TXN_NOSYNC
166 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)
167 flags: TXN_NOSYNC 198 flags: TXN_NOSYNC
168 199
169 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)
170 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.
171 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
172 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
173 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,
174 it contains the following extensions: 205 it contains the following extensions:
… …
199 230
200 You can use the "$txn->failed" method to check wether a transaction has 231 You can use the "$txn->failed" method to check wether a transaction has
201 failed in this way and abort further processing (excluding 232 failed in this way and abort further processing (excluding
202 "db_txn_finish"). 233 "db_txn_finish").
203 234
204 DB_ENV/database environment methods 235 DB_ENV/database environment methods
205 Methods available on DB_ENV/$env handles: 236 Methods available on DB_ENV/$env handles:
206 237
207 DESTROY (DB_ENV_ornull *env) 238 DESTROY (DB_ENV_ornull *env)
208 CODE: 239 CODE:
209 if (env) 240 if (env)
… …
212 $int = $env->set_data_dir (const char *dir) 243 $int = $env->set_data_dir (const char *dir)
213 $int = $env->set_tmp_dir (const char *dir) 244 $int = $env->set_tmp_dir (const char *dir)
214 $int = $env->set_lg_dir (const char *dir) 245 $int = $env->set_lg_dir (const char *dir)
215 $int = $env->set_shm_key (long shm_key) 246 $int = $env->set_shm_key (long shm_key)
216 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 247 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
217 $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)
218 $env->set_errfile (FILE *errfile = 0) 251 $env->set_errfile (FILE *errfile = 0)
219 $env->set_msgfile (FILE *msgfile = 0) 252 $env->set_msgfile (FILE *msgfile = 0)
220 $int = $env->set_verbose (U32 which, int onoff = 1) 253 $int = $env->set_verbose (U32 which, int onoff = 1)
221 $int = $env->set_encrypt (const char *password, U32 flags = 0) 254 $int = $env->set_encrypt (const char *password, U32 flags = 0)
222 $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)
… …
234 $int = $env->mutex_set_max (U32 max) 267 $int = $env->mutex_set_max (U32 max)
235 $int = $env->mutex_set_align (U32 align) 268 $int = $env->mutex_set_align (U32 align)
236 269
237 $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)
238 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)
239 273
240 Example: 274 Example:
241 use AnyEvent; 275 use AnyEvent;
242 use BDB; 276 use BDB;
243 277
… …
255 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,
256 0600; 290 0600;
257 291
258 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 292 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
259 293
260 DB/database methods 294 DB/database methods
261 Methods available on DB/$db handles: 295 Methods available on DB/$db handles:
262 296
263 DESTROY (DB_ornull *db) 297 DESTROY (DB_ornull *db)
264 CODE: 298 CODE:
265 if (db) 299 if (db)
… …
305 339
306 db_del $db, undef, "key $_" for 1..1000; 340 db_del $db, undef, "key $_" for 1..1000;
307 341
308 db_sync $db; 342 db_sync $db;
309 343
310 DB_TXN/transaction methods 344 DB_TXN/transaction methods
311 Methods available on DB_TXN/$txn handles: 345 Methods available on DB_TXN/$txn handles:
312 346
313 DESTROY (DB_TXN_ornull *txn) 347 DESTROY (DB_TXN_ornull *txn)
314 CODE: 348 CODE:
315 if (txn) 349 if (txn)
… …
319 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT 353 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
320 354
321 $bool = $txn->failed 355 $bool = $txn->failed
322 # see db_txn_finish documentation, above 356 # see db_txn_finish documentation, above
323 357
324 DBC/cursor methods 358 DBC/cursor methods
325 Methods available on DBC/$dbc handles: 359 Methods available on DBC/$dbc handles:
326 360
327 DESTROY (DBC_ornull *dbc) 361 DESTROY (DBC_ornull *dbc)
328 CODE: 362 CODE:
329 if (dbc) 363 if (dbc)
330 dbc->c_close (dbc); 364 dbc->c_close (dbc);
365
366 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
331 367
332 Example: 368 Example:
333 my $c = $db->cursor; 369 my $c = $db->cursor;
334 370
335 for (;;) { 371 for (;;) {
… …
338 last if $!; 374 last if $!;
339 } 375 }
340 376
341 db_c_close $c; 377 db_c_close $c;
342 378
343 DB_SEQUENCE/sequence methods 379 DB_SEQUENCE/sequence methods
344 Methods available on DB_SEQUENCE/$seq handles: 380 Methods available on DB_SEQUENCE/$seq handles:
345 381
346 DESTROY (DB_SEQUENCE_ornull *seq) 382 DESTROY (DB_SEQUENCE_ornull *seq)
347 CODE: 383 CODE:
348 if (seq) 384 if (seq)
… …
358 my $seq = $db->sequence; 394 my $seq = $db->sequence;
359 395
360 db_sequence_open $seq, undef, "seq", BDB::CREATE; 396 db_sequence_open $seq, undef, "seq", BDB::CREATE;
361 db_sequence_get $seq, undef, 1, my $value; 397 db_sequence_get $seq, undef, 1, my $value;
362 398
363 SUPPORT FUNCTIONS 399SUPPORT FUNCTIONS
364 EVENT PROCESSING AND EVENT LOOP INTEGRATION 400 EVENT PROCESSING AND EVENT LOOP INTEGRATION
401 $msg = BDB::strerror [$errno]
402 Returns the string corresponding to the given errno value. If no
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 $!.
408
365 $fileno = BDB::poll_fileno 409 $fileno = BDB::poll_fileno
366 Return the *request result pipe file descriptor*. This filehandle 410 Return the *request result pipe file descriptor*. This filehandle
367 must be polled for reading by some mechanism outside this module 411 must be polled for reading by some mechanism outside this module
368 (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
369 becomes readable you have to call "poll_cb" to check the results. 413 becomes readable you have to call "poll_cb" to check the results.
… …
438 Strictly equivalent to: 482 Strictly equivalent to:
439 483
440 BDB::poll_wait, BDB::poll_cb 484 BDB::poll_wait, BDB::poll_cb
441 while BDB::nreqs; 485 while BDB::nreqs;
442 486
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
443 CONTROLLING THE NUMBER OF THREADS 527 CONTROLLING THE NUMBER OF THREADS
444 BDB::min_parallel $nthreads 528 BDB::min_parallel $nthreads
445 Set the minimum number of BDB threads to $nthreads. The current 529 Set the minimum number of BDB threads to $nthreads. The current
446 default is 8, which means eight asynchronous operations can execute 530 default is 8, which means eight asynchronous operations can execute
447 concurrently at any one time (the number of outstanding requests, 531 concurrently at any one time (the number of outstanding requests,
448 however, is unlimited). 532 however, is unlimited).
… …
507 You can still queue as many requests as you want. Therefore, 591 You can still queue as many requests as you want. Therefore,
508 "max_oustsanding" is mainly useful in simple scripts (with low 592 "max_oustsanding" is mainly useful in simple scripts (with low
509 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
510 (with large values). 594 (with large values).
511 595
512 BDB::set_sync_prepare $cb 596 $old_cb = BDB::set_sync_prepare $cb
513 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
514 an explicit callback. It has to return two code references. The 598 an explicit callback. It has to return two code references. The
515 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
516 wait until the first callback has been called. The default 600 status), and the second is called to wait until the first callback
517 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:
518 609
519 sub { 610 sub {
520 my $status; 611 my $status;
521 ( 612 (
522 sub { $status = $! }, 613 sub { $status = $! },
523 sub { BDB::poll while !defined $status; $! = $status }, 614 sub { BDB::poll while !defined $status; $! = $status },
524 ) 615 )
525 } 616 }
526 617
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
527 STATISTICAL INFORMATION 626 STATISTICAL INFORMATION
528 BDB::nreqs 627 BDB::nreqs
529 Returns the number of requests currently in the ready, execute or 628 Returns the number of requests currently in the ready, execute or
530 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
531 yet). 630 yet).
532 631
… …
541 640
542 BDB::npending 641 BDB::npending
543 Returns the number of requests currently in the pending state 642 Returns the number of requests currently in the pending state
544 (executed, but not yet processed by poll_cb). 643 (executed, but not yet processed by poll_cb).
545 644
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 the same 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 (unless you use threads).
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
546 FORK BEHAVIOUR 665FORK BEHAVIOUR
547 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:
548 667
549 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
550 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
551 the parent simply leaves the quiescent state and continues 670 the parent simply leaves the quiescent state and continues
… …
556 675
557 In short: the parent will, after a short pause, continue as if fork had 676 In short: the parent will, after a short pause, continue as if fork had
558 not been called, while the child will act as if BDB has not been used 677 not been called, while the child will act as if BDB has not been used
559 yet. 678 yet.
560 679
680 Win32 note: there is no fork on win32, and perls emulation of it is too
681 broken to be supported, so do not use BDB in a windows pseudo-fork,
682 better yet, switch to a more capable platform.
683
561 MEMORY USAGE 684MEMORY USAGE
562 Per-request usage: 685 Per-request usage:
563 686
564 Each aio request uses - depending on your architecture - around 100-200 687 Each aio request uses - depending on your architecture - around 100-200
565 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
566 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
… …
574 697
575 In the execution phase, some aio requests require more memory for 698 In the execution phase, some aio requests require more memory for
576 temporary buffers, and each thread requires a stack and other data 699 temporary buffers, and each thread requires a stack and other data
577 structures (usually around 16k-128k, depending on the OS). 700 structures (usually around 16k-128k, depending on the OS).
578 701
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
579KNOWN BUGS 710KNOWN BUGS
580 Known bugs will be fixed in the next release, except: 711 Known bugs will be fixed in the next release, except:
581 712
582 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
583 with an operating system error or DB_LOCK_NOTGRANTED, the internal 714 with an operating system error or DB_LOCK_NOTGRANTED, the internal
584 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>,
585 above. 716 above.
586 717
587SEE ALSO 718SEE ALSO
588 Coro::BDB, IO::AIO. 719 AnyEvent::BDB (event loop integration), Coro::BDB (more natural syntax),
720 IO::AIO (nice to have).
589 721
590AUTHOR 722AUTHOR
591 Marc Lehmann <schmorp@schmorp.de> 723 Marc Lehmann <schmorp@schmorp.de>
592 http://home.schmorp.de/ 724 http://home.schmorp.de/
593 725

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