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Revision 1.4 by root, Fri Dec 7 13:39:04 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 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)
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)
129 159
130 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 160 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
131 flags: XA_CREATE 161 flags: XA_CREATE
132 162
133 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)
134 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
135 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 165 db_close (DB *db, U32 flags = 0, SV *callback = 0)
136 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)
168 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) 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)
138 flags: FREELIST_ONLY FREE_SPACE 170 flags: FREELIST_ONLY FREE_SPACE
139 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 171 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) 172 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) 173 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
142 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)
143 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)
144 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
145 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)
146 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
147 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)
148 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)
149 flags: TXN_NOSYNC TXN_SYNC 182 flags: TXN_NOSYNC TXN_SYNC
150 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 183 db_txn_abort (DB_TXN *txn, SV *callback = 0)
151 184
152 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 185 db_c_close (DBC *dbc, SV *callback = 0)
153 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)
154 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)
155 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA 188 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) 189 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 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
158 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)
159 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)
160 193
161 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)
162 flags: CREATE EXCL 195 flags: CREATE EXCL
163 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)
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) 197 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 198 flags: TXN_NOSYNC
166 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)
167 flags: TXN_NOSYNC 200 flags: TXN_NOSYNC
168 201
169 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)
170 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.
171 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
172 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
173 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,
174 it contains the following extensions: 207 it contains the following extensions:
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199 232
200 You can use the "$txn->failed" method to check wether a transaction has 233 You can use the "$txn->failed" method to check wether a transaction has
201 failed in this way and abort further processing (excluding 234 failed in this way and abort further processing (excluding
202 "db_txn_finish"). 235 "db_txn_finish").
203 236
204 DB_ENV/database environment methods 237 DB_ENV/database environment methods
205 Methods available on DB_ENV/$env handles: 238 Methods available on DB_ENV/$env handles:
206 239
207 DESTROY (DB_ENV_ornull *env) 240 DESTROY (DB_ENV_ornull *env)
208 CODE: 241 CODE:
209 if (env) 242 if (env)
… …
212 $int = $env->set_data_dir (const char *dir) 245 $int = $env->set_data_dir (const char *dir)
213 $int = $env->set_tmp_dir (const char *dir) 246 $int = $env->set_tmp_dir (const char *dir)
214 $int = $env->set_lg_dir (const char *dir) 247 $int = $env->set_lg_dir (const char *dir)
215 $int = $env->set_shm_key (long shm_key) 248 $int = $env->set_shm_key (long shm_key)
216 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 249 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
217 $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)
218 $env->set_errfile (FILE *errfile = 0) 253 $env->set_errfile (FILE *errfile = 0)
219 $env->set_msgfile (FILE *msgfile = 0) 254 $env->set_msgfile (FILE *msgfile = 0)
220 $int = $env->set_verbose (U32 which, int onoff = 1) 255 $int = $env->set_verbose (U32 which, int onoff = 1)
221 $int = $env->set_encrypt (const char *password, U32 flags = 0) 256 $int = $env->set_encrypt (const char *password, U32 flags = 0)
222 $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)
… …
234 $int = $env->mutex_set_max (U32 max) 269 $int = $env->mutex_set_max (U32 max)
235 $int = $env->mutex_set_align (U32 align) 270 $int = $env->mutex_set_align (U32 align)
236 271
237 $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)
238 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)
239 275
240 Example: 276 Example:
241 use AnyEvent; 277 use AnyEvent;
242 use BDB; 278 use BDB;
243 279
… …
255 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,
256 0600; 292 0600;
257 293
258 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 294 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
259 295
260 DB/database methods 296 DB/database methods
261 Methods available on DB/$db handles: 297 Methods available on DB/$db handles:
262 298
263 DESTROY (DB_ornull *db) 299 DESTROY (DB_ornull *db)
264 CODE: 300 CODE:
265 if (db) 301 if (db)
… …
305 341
306 db_del $db, undef, "key $_" for 1..1000; 342 db_del $db, undef, "key $_" for 1..1000;
307 343
308 db_sync $db; 344 db_sync $db;
309 345
310 DB_TXN/transaction methods 346 DB_TXN/transaction methods
311 Methods available on DB_TXN/$txn handles: 347 Methods available on DB_TXN/$txn handles:
312 348
313 DESTROY (DB_TXN_ornull *txn) 349 DESTROY (DB_TXN_ornull *txn)
314 CODE: 350 CODE:
315 if (txn) 351 if (txn)
… …
319 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT 355 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
320 356
321 $bool = $txn->failed 357 $bool = $txn->failed
322 # see db_txn_finish documentation, above 358 # see db_txn_finish documentation, above
323 359
324 DBC/cursor methods 360 DBC/cursor methods
325 Methods available on DBC/$dbc handles: 361 Methods available on DBC/$dbc handles:
326 362
327 DESTROY (DBC_ornull *dbc) 363 DESTROY (DBC_ornull *dbc)
328 CODE: 364 CODE:
329 if (dbc) 365 if (dbc)
330 dbc->c_close (dbc); 366 dbc->c_close (dbc);
367
368 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
331 369
332 Example: 370 Example:
333 my $c = $db->cursor; 371 my $c = $db->cursor;
334 372
335 for (;;) { 373 for (;;) {
… …
338 last if $!; 376 last if $!;
339 } 377 }
340 378
341 db_c_close $c; 379 db_c_close $c;
342 380
343 DB_SEQUENCE/sequence methods 381 DB_SEQUENCE/sequence methods
344 Methods available on DB_SEQUENCE/$seq handles: 382 Methods available on DB_SEQUENCE/$seq handles:
345 383
346 DESTROY (DB_SEQUENCE_ornull *seq) 384 DESTROY (DB_SEQUENCE_ornull *seq)
347 CODE: 385 CODE:
348 if (seq) 386 if (seq)
… …
358 my $seq = $db->sequence; 396 my $seq = $db->sequence;
359 397
360 db_sequence_open $seq, undef, "seq", BDB::CREATE; 398 db_sequence_open $seq, undef, "seq", BDB::CREATE;
361 db_sequence_get $seq, undef, 1, my $value; 399 db_sequence_get $seq, undef, 1, my $value;
362 400
363 SUPPORT FUNCTIONS 401SUPPORT FUNCTIONS
364 EVENT PROCESSING AND EVENT LOOP INTEGRATION 402 EVENT PROCESSING AND EVENT LOOP INTEGRATION
403 $msg = BDB::strerror [$errno]
404 Returns the string corresponding to the given errno value. If no
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 $!.
410
365 $fileno = BDB::poll_fileno 411 $fileno = BDB::poll_fileno
366 Return the *request result pipe file descriptor*. This filehandle 412 Return the *request result pipe file descriptor*. This filehandle
367 must be polled for reading by some mechanism outside this module 413 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 414 (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. 415 becomes readable you have to call "poll_cb" to check the results.
… …
438 Strictly equivalent to: 484 Strictly equivalent to:
439 485
440 BDB::poll_wait, BDB::poll_cb 486 BDB::poll_wait, BDB::poll_cb
441 while BDB::nreqs; 487 while BDB::nreqs;
442 488
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
443 CONTROLLING THE NUMBER OF THREADS 529 CONTROLLING THE NUMBER OF THREADS
444 BDB::min_parallel $nthreads 530 BDB::min_parallel $nthreads
445 Set the minimum number of BDB threads to $nthreads. The current 531 Set the minimum number of BDB threads to $nthreads. The current
446 default is 8, which means eight asynchronous operations can execute 532 default is 8, which means eight asynchronous operations can execute
447 concurrently at any one time (the number of outstanding requests, 533 concurrently at any one time (the number of outstanding requests,
448 however, is unlimited). 534 however, is unlimited).
… …
507 You can still queue as many requests as you want. Therefore, 593 You can still queue as many requests as you want. Therefore,
508 "max_oustsanding" is mainly useful in simple scripts (with low 594 "max_oustsanding" is mainly useful in simple scripts (with low
509 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
510 (with large values). 596 (with large values).
511 597
512 BDB::set_sync_prepare $cb 598 $old_cb = BDB::set_sync_prepare $cb
513 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
514 an explicit callback. It has to return two code references. The 600 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 601 first is used as the request callback (it should save the return
516 wait until the first callback has been called. The default 602 status), and the second is called to wait until the first callback
517 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:
518 611
519 sub { 612 sub {
520 my $status; 613 my $status;
521 ( 614 (
522 sub { $status = $! }, 615 sub { $status = $! },
523 sub { BDB::poll while !defined $status; $! = $status }, 616 sub { BDB::poll while !defined $status; $! = $status },
524 ) 617 )
525 } 618 }
526 619
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
527 STATISTICAL INFORMATION 628 STATISTICAL INFORMATION
528 BDB::nreqs 629 BDB::nreqs
529 Returns the number of requests currently in the ready, execute or 630 Returns the number of requests currently in the ready, execute or
530 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
531 yet). 632 yet).
532 633
… …
541 642
542 BDB::npending 643 BDB::npending
543 Returns the number of requests currently in the pending state 644 Returns the number of requests currently in the pending state
544 (executed, but not yet processed by poll_cb). 645 (executed, but not yet processed by poll_cb).
545 646
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
546 FORK BEHAVIOUR 667FORK BEHAVIOUR
547 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:
548 669
549 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
550 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
551 the parent simply leaves the quiescent state and continues 672 the parent simply leaves the quiescent state and continues
… …
556 677
557 In short: the parent will, after a short pause, continue as if fork had 678 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 679 not been called, while the child will act as if BDB has not been used
559 yet. 680 yet.
560 681
682 Win32 note: there is no fork on win32, and perls emulation of it is too
683 broken to be supported, so do not use BDB in a windows pseudo-fork,
684 better yet, switch to a more capable platform.
685
561 MEMORY USAGE 686MEMORY USAGE
562 Per-request usage: 687 Per-request usage:
563 688
564 Each aio request uses - depending on your architecture - around 100-200 689 Each aio request uses - depending on your architecture - around 100-200
565 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
566 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
… …
574 699
575 In the execution phase, some aio requests require more memory for 700 In the execution phase, some aio requests require more memory for
576 temporary buffers, and each thread requires a stack and other data 701 temporary buffers, and each thread requires a stack and other data
577 structures (usually around 16k-128k, depending on the OS). 702 structures (usually around 16k-128k, depending on the OS).
578 703
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
579KNOWN BUGS 712KNOWN BUGS
580 Known bugs will be fixed in the next release, except: 713 Known bugs will be fixed in the next release, except:
581 714
582 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
583 with an operating system error or DB_LOCK_NOTGRANTED, the internal 716 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>, 717 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
585 above. 718 above.
586 719
587SEE ALSO 720SEE ALSO
588 Coro::BDB, IO::AIO. 721 AnyEvent::BDB (event loop integration), Coro::BDB (more natural syntax),
722 IO::AIO (nice to have).
589 723
590AUTHOR 724AUTHOR
591 Marc Lehmann <schmorp@schmorp.de> 725 Marc Lehmann <schmorp@schmorp.de>
592 http://home.schmorp.de/ 726 http://home.schmorp.de/
593 727

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