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Revision 1.3 by root, Tue Dec 4 10:14:34 2007 UTC vs.
Revision 1.18 by root, Thu Jan 18 16:45:27 2018 UTC

1NAME 1NAME
2 BDB - Asynchronous Berkeley DB access 2 BDB - Asynchronous Berkeley DB access
3 3
4SYNOPSIS 4SYNOPSIS
5 use BDB; 5 use BDB;
6
7 my $env = db_env_create;
8
9 mkdir "bdtest", 0700;
10 db_env_open
11 $env,
12 "bdtest",
13 BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL
14 | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE,
15 0600;
16
17 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
18
19 my $db = db_create $env;
20 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE
21 | BDB::READ_UNCOMMITTED, 0600;
22 db_put $db, undef, "key", "data", 0, sub {
23 db_del $db, undef, "key";
24 };
25 db_sync $db;
26
27 # when you also use Coro, management is easy:
28 use Coro::BDB;
29
30 # automatic event loop integration with AnyEvent:
31 use AnyEvent::BDB;
32
33 # automatic result processing with EV:
34 my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
35
36 # with Glib:
37 add_watch Glib::IO BDB::poll_fileno,
38 in => sub { BDB::poll_cb; 1 };
39
40 # or simply flush manually
41 BDB::flush;
6 42
7DESCRIPTION 43DESCRIPTION
8 See the BerkeleyDB documentation 44 See the BerkeleyDB documentation
9 (<http://www.oracle.com/technology/documentation/berkeley-db/db/index.ht 45 (<http://www.oracle.com/technology/documentation/berkeley-db/db/index.ht
10 ml>). The BDB API is very similar to the C API (the translation has been 46 ml>). The BDB API is very similar to the C API (the translation has been
… …
50 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
51 anymore (except possibly for the Perl object, but its connection to 87 anymore (except possibly for the Perl object, but its connection to
52 the actual aio request is severed and calling its methods will 88 the actual aio request is severed and calling its methods will
53 either do nothing or result in a runtime error). 89 either do nothing or result in a runtime error).
54 90
55 BERKELEYDB FUNCTIONS 91BERKELEYDB FUNCTIONS
56 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
57 object and never block. All the remaining functions all take an optional 93 object and never block. All the remaining functions take an optional
58 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
59 executed synchronously. 95 executed synchronously. In both cases, $! will reflect the return value
96 of the function.
60 97
61 BDB functions that cannot block (mostly functions that manipulate 98 BDB functions that cannot block (mostly functions that manipulate
62 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
63 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
64 callback as last argument. 101 callback as last argument.
65 102
66 In the following, $int signifies an integer return value, "octetstring" 103 In the following, $int signifies an integer return value, "bdb_filename"
67 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
68 >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
69 is a floating point value. 106 value.
70 107
71 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
72 values), and the "SV *callback" is the optional callback function to 109 values).
73 call when the request is completed.
74 110
75 The various "DB_ENV" etc. arguments are handles return by 111 The various "DB_ENV" etc. arguments are handles return by
76 "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
77 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"
78 for them, resulting a NULL pointer on the C level. 114 for them, resulting a NULL pointer on the C level.
79 115
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
80 BDB functions 139 BDB functions
81 Functions in the BDB namespace, exported by default: 140 Functions in the BDB namespace, exported by default:
82 141
83 $env = db_env_create (U32 env_flags = 0) 142 $env = db_env_create (U32 env_flags = 0)
84 flags: RPCCLIENT 143 flags: RPCCLIENT
85 144
86 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)
87 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
88 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)
89 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)
90 flags: FORCE 149 flags: FORCE
91 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)
92 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
93 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)
94 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)
95 159
96 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 160 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
97 flags: XA_CREATE 161 flags: XA_CREATE
98 162
99 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)
100 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
101 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 165 db_close (DB *db, U32 flags = 0, SV *callback = 0)
102 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)
103 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)
104 flags: FREELIST_ONLY FREE_SPACE 170 flags: FREELIST_ONLY FREE_SPACE
105 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 171 db_sync (DB *db, U32 flags = 0, SV *callback = 0)
106 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)
107 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)
108 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)
109 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)
110 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
111 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)
112 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
113 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)
114 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)
115 flags: TXN_NOSYNC TXN_SYNC 182 flags: TXN_NOSYNC TXN_SYNC
116 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 183 db_txn_abort (DB_TXN *txn, SV *callback = 0)
117 184
118 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 185 db_c_close (DBC *dbc, SV *callback = 0)
119 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)
120 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)
121 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA 188 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
122 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)
123 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
124 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)
125 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)
126 193
127 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)
128 flags: CREATE EXCL 195 flags: CREATE EXCL
129 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)
130 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)
131 flags: TXN_NOSYNC 198 flags: TXN_NOSYNC
132 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)
133 flags: TXN_NOSYNC 200 flags: TXN_NOSYNC
134 201
135 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)
136 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.
137 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
138 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
139 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,
140 it contains the following extensions: 207 it contains the following extensions:
… …
165 232
166 You can use the "$txn->failed" method to check wether a transaction has 233 You can use the "$txn->failed" method to check wether a transaction has
167 failed in this way and abort further processing (excluding 234 failed in this way and abort further processing (excluding
168 "db_txn_finish"). 235 "db_txn_finish").
169 236
170 DB_ENV/database environment methods 237 DB_ENV/database environment methods
171 Methods available on DB_ENV/$env handles: 238 Methods available on DB_ENV/$env handles:
172 239
173 DESTROY (DB_ENV_ornull *env) 240 DESTROY (DB_ENV_ornull *env)
174 CODE: 241 CODE:
175 if (env) 242 if (env)
… …
178 $int = $env->set_data_dir (const char *dir) 245 $int = $env->set_data_dir (const char *dir)
179 $int = $env->set_tmp_dir (const char *dir) 246 $int = $env->set_tmp_dir (const char *dir)
180 $int = $env->set_lg_dir (const char *dir) 247 $int = $env->set_lg_dir (const char *dir)
181 $int = $env->set_shm_key (long shm_key) 248 $int = $env->set_shm_key (long shm_key)
182 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 249 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
183 $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)
184 $env->set_errfile (FILE *errfile = 0) 253 $env->set_errfile (FILE *errfile = 0)
185 $env->set_msgfile (FILE *msgfile = 0) 254 $env->set_msgfile (FILE *msgfile = 0)
186 $int = $env->set_verbose (U32 which, int onoff = 1) 255 $int = $env->set_verbose (U32 which, int onoff = 1)
187 $int = $env->set_encrypt (const char *password, U32 flags = 0) 256 $int = $env->set_encrypt (const char *password, U32 flags = 0)
188 $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)
… …
193 $int = $env->set_lk_max_lockers (U32 max) 262 $int = $env->set_lk_max_lockers (U32 max)
194 $int = $env->set_lk_max_locks (U32 max) 263 $int = $env->set_lk_max_locks (U32 max)
195 $int = $env->set_lk_max_objects (U32 max) 264 $int = $env->set_lk_max_objects (U32 max)
196 $int = $env->set_lg_bsize (U32 max) 265 $int = $env->set_lg_bsize (U32 max)
197 $int = $env->set_lg_max (U32 max) 266 $int = $env->set_lg_max (U32 max)
267 $int = $env->mutex_set_increment (U32 increment)
268 $int = $env->mutex_set_tas_spins (U32 tas_spins)
269 $int = $env->mutex_set_max (U32 max)
270 $int = $env->mutex_set_align (U32 align)
198 271
199 $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)
200 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)
201 275
202 Example: 276 Example:
203 use AnyEvent; 277 use AnyEvent;
204 use BDB; 278 use BDB;
205 279
… …
217 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,
218 0600; 292 0600;
219 293
220 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 294 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
221 295
222 DB/database methods 296 DB/database methods
223 Methods available on DB/$db handles: 297 Methods available on DB/$db handles:
224 298
225 DESTROY (DB_ornull *db) 299 DESTROY (DB_ornull *db)
226 CODE: 300 CODE:
227 if (db) 301 if (db)
… …
267 341
268 db_del $db, undef, "key $_" for 1..1000; 342 db_del $db, undef, "key $_" for 1..1000;
269 343
270 db_sync $db; 344 db_sync $db;
271 345
272 DB_TXN/transaction methods 346 DB_TXN/transaction methods
273 Methods available on DB_TXN/$txn handles: 347 Methods available on DB_TXN/$txn handles:
274 348
275 DESTROY (DB_TXN_ornull *txn) 349 DESTROY (DB_TXN_ornull *txn)
276 CODE: 350 CODE:
277 if (txn) 351 if (txn)
… …
281 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT 355 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
282 356
283 $bool = $txn->failed 357 $bool = $txn->failed
284 # see db_txn_finish documentation, above 358 # see db_txn_finish documentation, above
285 359
286 DBC/cursor methods 360 DBC/cursor methods
287 Methods available on DBC/$dbc handles: 361 Methods available on DBC/$dbc handles:
288 362
289 DESTROY (DBC_ornull *dbc) 363 DESTROY (DBC_ornull *dbc)
290 CODE: 364 CODE:
291 if (dbc) 365 if (dbc)
292 dbc->c_close (dbc); 366 dbc->c_close (dbc);
367
368 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
293 369
294 Example: 370 Example:
295 my $c = $db->cursor; 371 my $c = $db->cursor;
296 372
297 for (;;) { 373 for (;;) {
… …
300 last if $!; 376 last if $!;
301 } 377 }
302 378
303 db_c_close $c; 379 db_c_close $c;
304 380
305 DB_SEQUENCE/sequence methods 381 DB_SEQUENCE/sequence methods
306 Methods available on DB_SEQUENCE/$seq handles: 382 Methods available on DB_SEQUENCE/$seq handles:
307 383
308 DESTROY (DB_SEQUENCE_ornull *seq) 384 DESTROY (DB_SEQUENCE_ornull *seq)
309 CODE: 385 CODE:
310 if (seq) 386 if (seq)
… …
320 my $seq = $db->sequence; 396 my $seq = $db->sequence;
321 397
322 db_sequence_open $seq, undef, "seq", BDB::CREATE; 398 db_sequence_open $seq, undef, "seq", BDB::CREATE;
323 db_sequence_get $seq, undef, 1, my $value; 399 db_sequence_get $seq, undef, 1, my $value;
324 400
325 SUPPORT FUNCTIONS 401SUPPORT FUNCTIONS
326 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
327 $fileno = BDB::poll_fileno 411 $fileno = BDB::poll_fileno
328 Return the *request result pipe file descriptor*. This filehandle 412 Return the *request result pipe file descriptor*. This filehandle
329 must be polled for reading by some mechanism outside this module 413 must be polled for reading by some mechanism outside this module
330 (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
331 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.
… …
367 interactiveness when perl is not fast enough to process all requests 451 interactiveness when perl is not fast enough to process all requests
368 in time. 452 in time.
369 453
370 For interactive programs, values such as 0.01 to 0.1 should be fine. 454 For interactive programs, values such as 0.01 to 0.1 should be fine.
371 455
372 Example: Install an Event watcher that automatically calls 456 Example: Install an EV watcher that automatically calls BDB::poll_cb
373 BDB::poll_cb with low priority, to ensure that other parts of the 457 with low priority, to ensure that other parts of the program get the
374 program get the CPU sometimes even under high AIO load. 458 CPU sometimes even under high load.
375 459
376 # try not to spend much more than 0.1s in poll_cb 460 # try not to spend much more than 0.1s in poll_cb
377 BDB::max_poll_time 0.1; 461 BDB::max_poll_time 0.1;
378 462
379 # use a low priority so other tasks have priority 463 my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
380 Event->io (fd => BDB::poll_fileno,
381 poll => 'r', nice => 1,
382 cb => &BDB::poll_cb);
383 464
384 BDB::poll_wait 465 BDB::poll_wait
385 If there are any outstanding requests and none of them in the result 466 If there are any outstanding requests and none of them in the result
386 phase, wait till the result filehandle becomes ready for reading 467 phase, wait till the result filehandle becomes ready for reading
387 (simply does a "select" on the filehandle. This is useful if you 468 (simply does a "select" on the filehandle. This is useful if you
… …
396 equivalent to: 477 equivalent to:
397 478
398 BDB::poll_wait, BDB::poll_cb 479 BDB::poll_wait, BDB::poll_cb
399 480
400 BDB::flush 481 BDB::flush
401 Wait till all outstanding AIO requests have been handled. 482 Wait till all outstanding BDB requests have been handled.
402 483
403 Strictly equivalent to: 484 Strictly equivalent to:
404 485
405 BDB::poll_wait, BDB::poll_cb 486 BDB::poll_wait, BDB::poll_cb
406 while BDB::nreqs; 487 while BDB::nreqs;
407 488
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
408 CONTROLLING THE NUMBER OF THREADS 529 CONTROLLING THE NUMBER OF THREADS
409 BDB::min_parallel $nthreads 530 BDB::min_parallel $nthreads
410 Set the minimum number of AIO threads to $nthreads. The current 531 Set the minimum number of BDB threads to $nthreads. The current
411 default is 8, which means eight asynchronous operations can execute 532 default is 8, which means eight asynchronous operations can execute
412 concurrently at any one time (the number of outstanding requests, 533 concurrently at any one time (the number of outstanding requests,
413 however, is unlimited). 534 however, is unlimited).
414 535
415 BDB starts threads only on demand, when an AIO request is queued and 536 BDB starts threads only on demand, when an BDB request is queued and
416 no free thread exists. Please note that queueing up a hundred 537 no free thread exists. Please note that queueing up a hundred
417 requests can create demand for a hundred threads, even if it turns 538 requests can create demand for a hundred threads, even if it turns
418 out that everything is in the cache and could have been processed 539 out that everything is in the cache and could have been processed
419 faster by a single thread. 540 faster by a single thread.
420 541
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426 Under most circumstances you don't need to call this function, as 547 Under most circumstances you don't need to call this function, as
427 the module selects a default that is suitable for low to moderate 548 the module selects a default that is suitable for low to moderate
428 load. 549 load.
429 550
430 BDB::max_parallel $nthreads 551 BDB::max_parallel $nthreads
431 Sets the maximum number of AIO threads to $nthreads. If more than 552 Sets the maximum number of BDB threads to $nthreads. If more than
432 the specified number of threads are currently running, this function 553 the specified number of threads are currently running, this function
433 kills them. This function blocks until the limit is reached. 554 kills them. This function blocks until the limit is reached.
434 555
435 While $nthreads are zero, aio requests get queued but not executed 556 While $nthreads are zero, aio requests get queued but not executed
436 until the number of threads has been increased again. 557 until the number of threads has been increased again.
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472 You can still queue as many requests as you want. Therefore, 593 You can still queue as many requests as you want. Therefore,
473 "max_oustsanding" is mainly useful in simple scripts (with low 594 "max_oustsanding" is mainly useful in simple scripts (with low
474 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
475 (with large values). 596 (with large values).
476 597
477 BDB::set_sync_prepare $cb 598 $old_cb = BDB::set_sync_prepare $cb
478 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
479 an explicit callback. It has to return two code references. The 600 an explicit callback. It has to return two code references. The
480 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
481 wait until the first callback has been called. The default 602 status), and the second is called to wait until the first callback
482 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:
483 611
484 sub { 612 sub {
485 my $status; 613 my $status;
486 ( 614 (
487 sub { $status = $! }, 615 sub { $status = $! },
488 sub { BDB::poll while !defined $status; $! = $status }, 616 sub { BDB::poll while !defined $status; $! = $status },
489 ) 617 )
490 } 618 }
491 619
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
492 STATISTICAL INFORMATION 628 STATISTICAL INFORMATION
493 BDB::nreqs 629 BDB::nreqs
494 Returns the number of requests currently in the ready, execute or 630 Returns the number of requests currently in the ready, execute or
495 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
496 yet). 632 yet).
497 633
… …
506 642
507 BDB::npending 643 BDB::npending
508 Returns the number of requests currently in the pending state 644 Returns the number of requests currently in the pending state
509 (executed, but not yet processed by poll_cb). 645 (executed, but not yet processed by poll_cb).
510 646
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
511 FORK BEHAVIOUR 667FORK BEHAVIOUR
512 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:
513 669
514 Before the fork, IO::AIO enters a quiescent state where no requests can 670 Before the fork, BDB enters a quiescent state where no requests can be
515 be added in other threads and no results will be processed. After the 671 added in other threads and no results will be processed. After the fork
516 fork the parent simply leaves the quiescent state and continues 672 the parent simply leaves the quiescent state and continues
517 request/result processing, while the child frees the request/result 673 request/result processing, while the child frees the request/result
518 queue (so that the requests started before the fork will only be handled 674 queue (so that the requests started before the fork will only be handled
519 in the parent). Threads will be started on demand until the limit set in 675 in the parent). Threads will be started on demand until the limit set in
520 the parent process has been reached again. 676 the parent process has been reached again.
521 677
522 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
523 not been called, while the child will act as if IO::AIO has not been 679 not been called, while the child will act as if BDB has not been used
524 used yet. 680 yet.
525 681
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
526 MEMORY USAGE 686MEMORY USAGE
527 Per-request usage: 687 Per-request usage:
528 688
529 Each aio request uses - depending on your architecture - around 100-200 689 Each aio request uses - depending on your architecture - around 100-200
530 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
531 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
… …
539 699
540 In the execution phase, some aio requests require more memory for 700 In the execution phase, some aio requests require more memory for
541 temporary buffers, and each thread requires a stack and other data 701 temporary buffers, and each thread requires a stack and other data
542 structures (usually around 16k-128k, depending on the OS). 702 structures (usually around 16k-128k, depending on the OS).
543 703
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
544KNOWN BUGS 712KNOWN BUGS
545 Known bugs will be fixed in the next release, except: 713 Known bugs will be fixed in the next release, except:
546 714
547 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
548 with an operating system error or DB_LOCK_NOTGRANTED, the internal 716 with an operating system error or DB_LOCK_NOTGRANTED, the internal
549 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>,
550 above. 718 above.
551 719
552SEE ALSO 720SEE ALSO
553 Coro::AIO. 721 AnyEvent::BDB (event loop integration), Coro::BDB (more natural syntax),
722 IO::AIO (nice to have).
554 723
555AUTHOR 724AUTHOR
556 Marc Lehmann <schmorp@schmorp.de> 725 Marc Lehmann <schmorp@schmorp.de>
557 http://home.schmorp.de/ 726 http://home.schmorp.de/
558 727

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