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Comparing BDB/BDB.pm (file contents):
Revision 1.14 by root, Thu Sep 13 12:29:49 2007 UTC vs.
Revision 1.64 by root, Mon Dec 26 01:46:33 2011 UTC

… …
3BDB - Asynchronous Berkeley DB access 3BDB - Asynchronous Berkeley DB access
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use BDB; 7 use BDB;
8
9 my $env = db_env_create;
10
11 mkdir "bdtest", 0700;
12 db_env_open
13 $env,
14 "bdtest",
15 BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL
16 | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE,
17 0600;
18
19 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
20
21 my $db = db_create $env;
22 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE
23 | BDB::READ_UNCOMMITTED, 0600;
24 db_put $db, undef, "key", "data", 0, sub {
25 db_del $db, undef, "key";
26 };
27 db_sync $db;
28
29 # when you also use Coro, management is easy:
30 use Coro::BDB;
31
32 # automatic event loop integration with AnyEvent:
33 use AnyEvent::BDB;
34
35 # automatic result processing with EV:
36 my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
37
38 # with Glib:
39 add_watch Glib::IO BDB::poll_fileno,
40 in => sub { BDB::poll_cb; 1 };
41
42 # or simply flush manually
43 BDB::flush;
44
8 45
9=head1 DESCRIPTION 46=head1 DESCRIPTION
10 47
11See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). 48See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
12The BDB API is very similar to the C API (the translation has been very faithful). 49The BDB API is very similar to the C API (the translation has been very faithful).
… …
66 103
67=cut 104=cut
68 105
69package BDB; 106package BDB;
70 107
71no warnings; 108use common::sense;
72use strict 'vars';
73 109
74use base 'Exporter'; 110use base 'Exporter';
75 111
112our $VERSION;
113
76BEGIN { 114BEGIN {
77 our $VERSION = '1.0'; 115 $VERSION = '1.9';
78 116
79 our @BDB_REQ = qw( 117 our @BDB_REQ = qw(
80 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect 118 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
81 db_env_memp_sync db_env_memp_trickle 119 db_env_memp_sync db_env_memp_trickle db_env_dbrename db_env_dbremove
82 db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range 120 db_env_log_archive
121 db_open db_close db_compact db_sync db_verify db_upgrade
122 db_put db_exists db_get db_pget db_del db_key_range
83 db_txn_commit db_txn_abort 123 db_txn_commit db_txn_abort db_txn_finish
84 db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del 124 db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
85 db_sequence_open db_sequence_close 125 db_sequence_open db_sequence_close
86 db_sequence_get db_sequence_remove 126 db_sequence_get db_sequence_remove
87 ); 127 );
88 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create)); 128 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
… …
95 135
96 require XSLoader; 136 require XSLoader;
97 XSLoader::load ("BDB", $VERSION); 137 XSLoader::load ("BDB", $VERSION);
98} 138}
99 139
100=head2 BERKELEYDB FUNCTIONS 140=head1 BERKELEYDB FUNCTIONS
101 141
102All of these are functions. The create functions simply return a new 142All of these are functions. The create functions simply return a new
103object and never block. All the remaining functions all take an optional 143object and never block. All the remaining functions take an optional
104callback as last argument. If it is missing, then the fucntion will be 144callback as last argument. If it is missing, then the function will be
105executed synchronously. 145executed synchronously. In both cases, C<$!> will reflect the return value
146of the function.
106 147
107BDB functions that cannot block (mostly functions that manipulate 148BDB functions that cannot block (mostly functions that manipulate
108settings) are method calls on the relevant objects, so the rule of thumb 149settings) are method calls on the relevant objects, so the rule of thumb
109is: if its a method, its not blocking, if its a function, it takes a 150is: if it's a method, it's not blocking, if it's a function, it takes a
110callback as last argument. 151callback as last argument.
111 152
112In the following, C<$int> signifies an integer return value, 153In the following, C<$int> signifies an integer return value,
113C<octetstring> is a "binary string" (i.e. a perl string with no character 154C<bdb_filename> is a "filename" (octets on unix, madness on windows),
114indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some 155C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
115integer, C<NV> is a floating point value. 156floating point value.
116 157
117The C<SV *> types are generic perl scalars (for input and output of data 158Most C<SV *> types are generic perl scalars (for input and output of data
118values), and the C<SV *callback> is the optional callback function to call 159values).
119when the request is completed.
120 160
121The various C<DB_ENV> etc. arguments are handles return by 161The various C<DB_ENV> etc. arguments are handles return by
122C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an 162C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
123appended C<_ornull> this means they are optional and you can pass C<undef> 163appended C<_ornull> this means they are optional and you can pass C<undef>
124for them, resulting a NULL pointer on the C level. 164for them, resulting a NULL pointer on the C level.
125 165
166The C<SV *callback> is the optional callback function to call when the
167request is completed. This last callback argument is special: the callback
168is simply the last argument passed. If there are "optional" arguments
169before the callback they can be left out. The callback itself can be left
170out or specified as C<undef>, in which case the function will be executed
171synchronously.
172
173For example, C<db_env_txn_checkpoint> usually is called with all integer
174arguments zero. These can be left out, so all of these specify a call
175to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
176callback to be called:
177
178 db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
179 db_env_txn_checkpoint $db_env, 0, 0, sub { };
180 db_env_txn_checkpoint $db_env, sub { };
181
182While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
183executed synchronously:
184
185 db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
186 db_env_txn_checkpoint $db_env, 0, 0, 0;
187 db_env_txn_checkpoint $db_env, 0;
188
126=head3 BDB functions 189=head2 BDB functions
127 190
128Functions in the BDB namespace, exported by default: 191Functions in the BDB namespace, exported by default:
129 192
130 $env = db_env_create (U32 env_flags = 0) 193 $env = db_env_create (U32 env_flags = 0)
131 flags: RPCCLIENT 194 flags: RPCCLIENT
132 195
133 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 196 db_env_open (DB_ENV *env, bdb_filename db_home, U32 open_flags, int mode, SV *callback = 0)
134 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 197 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
135 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) 198 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = 0)
136 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 199 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = 0)
137 flags: FORCE 200 flags: FORCE
138 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) 201 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = 0)
139 atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST 202 atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
140 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) 203 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = 0)
141 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) 204 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = 0)
205 db_env_dbremove (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = 0)
206 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)
207 db_env_log_archive (DB_ENV *env, SV *listp, U32 flags = 0, SV *callback = 0)
142 208
143 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 209 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
144 flags: XA_CREATE 210 flags: XA_CREATE
145 211
146 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 212 db_open (DB *db, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = 0)
147 flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE 213 flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
148 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 214 db_close (DB *db, U32 flags = 0, SV *callback = 0)
149 flags: DB_NOSYNC 215 flags: DB_NOSYNC
216 db_verify (DB *db, bdb_filename file, bdb_filename database = 0, SV *dummy = 0, U32 flags = 0, SV *callback = 0)
217 db_upgrade (DB *db, bdb_filename file, U32 flags = 0, SV *callback = 0)
150 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) 218 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)
151 flags: FREELIST_ONLY FREE_SPACE 219 flags: FREELIST_ONLY FREE_SPACE
152 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 220 db_sync (DB *db, U32 flags = 0, SV *callback = 0)
153 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) 221 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = 0)
154 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 222 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
155 flags: APPEND NODUPDATA NOOVERWRITE 223 flags: APPEND NODUPDATA NOOVERWRITE
224 db_exists (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = 0) (v4.6)
156 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 225 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
157 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW 226 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
158 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 227 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = 0)
159 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW 228 flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
160 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 229 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = 0)
161 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) 230 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = 0)
162 flags: TXN_NOSYNC TXN_SYNC 231 flags: TXN_NOSYNC TXN_SYNC
163 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 232 db_txn_abort (DB_TXN *txn, SV *callback = 0)
164 233
165 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 234 db_c_close (DBC *dbc, SV *callback = 0)
166 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) 235 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = 0)
167 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 236 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
168 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA 237 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
169 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 238 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
170 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 239 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
171 db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 240 db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = 0)
172 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef) 241 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = 0)
173 242
174 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 243 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = 0)
175 flags: CREATE EXCL 244 flags: CREATE EXCL
176 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 245 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = 0)
177 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) 246 db_sequence_get (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, int delta, SV *seq_value, U32 flags = DB_TXN_NOSYNC, SV *callback = 0)
178 flags: TXN_NOSYNC 247 flags: TXN_NOSYNC
179 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 248 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = 0)
180 flags: TXN_NOSYNC 249 flags: TXN_NOSYNC
181 250
251=head3 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = 0)
252
253This is not actually a Berkeley DB function but a BDB module
254extension. The background for this exytension is: It is very annoying to
255have to check every single BDB function for error returns and provide a
256codepath out of your transaction. While the BDB module still makes this
257possible, it contains the following extensions:
258
259When a transaction-protected function returns any operating system
260error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
261transaction. This flag is also set by Berkeley DB functions themselves
262when an operation fails with LOCK_DEADLOCK, and it causes all further
263operations on that transaction (including C<db_txn_commit>) to fail.
264
265The C<db_txn_finish> request will look at this flag, and, if it is set,
266will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
267if it isn't set to something else yet). If it isn't set, it will call
268C<db_txn_commit> and return the error normally.
269
270How to use this? Easy: just write your transaction normally:
271
272 my $txn = $db_env->txn_begin;
273 db_get $db, $txn, "key", my $data;
274 db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
275 db_txn_finish $txn;
276 die "transaction failed" if $!;
277
278That is, handle only the expected errors. If something unexpected happens
279(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
280requests (db_put in this case) will simply be skipped (they will fail with
281LOCK_DEADLOCK) and the transaction will be aborted.
282
283You can use the C<< $txn->failed >> method to check wether a transaction
284has failed in this way and abort further processing (excluding
285C<db_txn_finish>).
286
287
182=head3 DB_ENV/database environment methods 288=head2 DB_ENV/database environment methods
183 289
184Methods available on DB_ENV/$env handles: 290Methods available on DB_ENV/$env handles:
185 291
186 DESTROY (DB_ENV_ornull *env) 292 DESTROY (DB_ENV_ornull *env)
187 CODE: 293 CODE:
… …
191 $int = $env->set_data_dir (const char *dir) 297 $int = $env->set_data_dir (const char *dir)
192 $int = $env->set_tmp_dir (const char *dir) 298 $int = $env->set_tmp_dir (const char *dir)
193 $int = $env->set_lg_dir (const char *dir) 299 $int = $env->set_lg_dir (const char *dir)
194 $int = $env->set_shm_key (long shm_key) 300 $int = $env->set_shm_key (long shm_key)
195 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 301 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
196 $int = $env->set_flags (U32 flags, int onoff) 302 $int = $env->set_flags (U32 flags, int onoff = 1)
303 $int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
304 $int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
197 $env->set_errfile (FILE *errfile = 0) 305 $env->set_errfile (FILE *errfile = 0)
198 $env->set_msgfile (FILE *msgfile = 0) 306 $env->set_msgfile (FILE *msgfile = 0)
199 $int = $env->set_verbose (U32 which, int onoff = 1) 307 $int = $env->set_verbose (U32 which, int onoff = 1)
200 $int = $env->set_encrypt (const char *password, U32 flags = 0) 308 $int = $env->set_encrypt (const char *password, U32 flags = 0)
201 $int = $env->set_timeout (NV timeout, U32 flags) 309 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
202 $int = $env->set_mp_max_openfd (int maxopenfd); 310 $int = $env->set_mp_max_openfd (int maxopenfd);
203 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); 311 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
204 $int = $env->set_mp_mmapsize (int mmapsize_mb) 312 $int = $env->set_mp_mmapsize (int mmapsize_mb)
205 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) 313 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
206 $int = $env->set_lk_max_lockers (U32 max) 314 $int = $env->set_lk_max_lockers (U32 max)
207 $int = $env->set_lk_max_locks (U32 max) 315 $int = $env->set_lk_max_locks (U32 max)
208 $int = $env->set_lk_max_objects (U32 max) 316 $int = $env->set_lk_max_objects (U32 max)
209 $int = $env->set_lg_bsize (U32 max) 317 $int = $env->set_lg_bsize (U32 max)
210 $int = $env->set_lg_max (U32 max) 318 $int = $env->set_lg_max (U32 max)
319 $int = $env->mutex_set_increment (U32 increment)
320 $int = $env->mutex_set_tas_spins (U32 tas_spins)
321 $int = $env->mutex_set_max (U32 max)
322 $int = $env->mutex_set_align (U32 align)
211 323
212 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 324 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
213 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC 325 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
326 $txn = $env->cdsgroup_begin; (v4.5)
214 327
215=head4 Example: 328=head3 Example:
216 329
217 use AnyEvent; 330 use AnyEvent;
218 use BDB; 331 use BDB;
219 332
220 our $FH; open $FH, "<&=" . BDB::poll_fileno; 333 our $FH; open $FH, "<&=" . BDB::poll_fileno;
… …
232 0600; 345 0600;
233 346
234 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 347 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
235 348
236 349
237=head3 DB/database methods 350=head2 DB/database methods
238 351
239Methods available on DB/$db handles: 352Methods available on DB/$db handles:
240 353
241 DESTROY (DB_ornull *db) 354 DESTROY (DB_ornull *db)
242 CODE: 355 CODE:
… …
268 381
269 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 382 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
270 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT 383 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
271 $seq = $db->sequence (U32 flags = 0) 384 $seq = $db->sequence (U32 flags = 0)
272 385
273=head4 Example: 386=head3 Example:
274 387
275 my $db = db_create $env; 388 my $db = db_create $env;
276 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600; 389 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600;
277 390
278 for (1..1000) { 391 for (1..1000) {
… …
285 db_del $db, undef, "key $_" for 1..1000; 398 db_del $db, undef, "key $_" for 1..1000;
286 399
287 db_sync $db; 400 db_sync $db;
288 401
289 402
290=head3 DB_TXN/transaction methods 403=head2 DB_TXN/transaction methods
291 404
292Methods available on DB_TXN/$txn handles: 405Methods available on DB_TXN/$txn handles:
293 406
294 DESTROY (DB_TXN_ornull *txn) 407 DESTROY (DB_TXN_ornull *txn)
295 CODE: 408 CODE:
296 if (txn) 409 if (txn)
297 txn->abort (txn); 410 txn->abort (txn);
298 411
299 $int = $txn->set_timeout (NV timeout, U32 flags) 412 $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
300 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT 413 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
301 414
415 $bool = $txn->failed
416 # see db_txn_finish documentation, above
302 417
418
303=head3 DBC/cursor methods 419=head2 DBC/cursor methods
304 420
305Methods available on DBC/$dbc handles: 421Methods available on DBC/$dbc handles:
306 422
307 DESTROY (DBC_ornull *dbc) 423 DESTROY (DBC_ornull *dbc)
308 CODE: 424 CODE:
309 if (dbc) 425 if (dbc)
310 dbc->c_close (dbc); 426 dbc->c_close (dbc);
311 427
428 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
429
312=head4 Example: 430=head3 Example:
313 431
314 my $c = $db->cursor; 432 my $c = $db->cursor;
315 433
316 for (;;) { 434 for (;;) {
317 db_c_get $c, my $key, my $data, BDB::NEXT; 435 db_c_get $c, my $key, my $data, BDB::NEXT;
… …
320 } 438 }
321 439
322 db_c_close $c; 440 db_c_close $c;
323 441
324 442
325=head3 DB_SEQUENCE/sequence methods 443=head2 DB_SEQUENCE/sequence methods
326 444
327Methods available on DB_SEQUENCE/$seq handles: 445Methods available on DB_SEQUENCE/$seq handles:
328 446
329 DESTROY (DB_SEQUENCE_ornull *seq) 447 DESTROY (DB_SEQUENCE_ornull *seq)
330 CODE: 448 CODE:
… …
335 $int = $seq->set_cachesize (U32 size) 453 $int = $seq->set_cachesize (U32 size)
336 $int = $seq->set_flags (U32 flags) 454 $int = $seq->set_flags (U32 flags)
337 flags: SEQ_DEC SEQ_INC SEQ_WRAP 455 flags: SEQ_DEC SEQ_INC SEQ_WRAP
338 $int = $seq->set_range (db_seq_t min, db_seq_t max) 456 $int = $seq->set_range (db_seq_t min, db_seq_t max)
339 457
340=head4 Example: 458=head3 Example:
341 459
342 my $seq = $db->sequence; 460 my $seq = $db->sequence;
343 461
344 db_sequence_open $seq, undef, "seq", BDB::CREATE; 462 db_sequence_open $seq, undef, "seq", BDB::CREATE;
345 db_sequence_get $seq, undef, 1, my $value; 463 db_sequence_get $seq, undef, 1, my $value;
346 464
347 465
348=head2 SUPPORT FUNCTIONS 466=head1 SUPPORT FUNCTIONS
349 467
350=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 468=head2 EVENT PROCESSING AND EVENT LOOP INTEGRATION
351 469
352=over 4 470=over 4
471
472=item $msg = BDB::strerror [$errno]
473
474Returns the string corresponding to the given errno value. If no argument
475is given, use C<$!>.
476
477Note that the BDB module also patches the C<$!> variable directly, so you
478should be able to get a bdb error string by simply stringifying C<$!>.
353 479
354=item $fileno = BDB::poll_fileno 480=item $fileno = BDB::poll_fileno
355 481
356Return the I<request result pipe file descriptor>. This filehandle must be 482Return the I<request result pipe file descriptor>. This filehandle must be
357polled for reading by some mechanism outside this module (e.g. Event or 483polled for reading by some mechanism outside this module (e.g. Event or
… …
396interactiveness when perl is not fast enough to process all requests in 522interactiveness when perl is not fast enough to process all requests in
397time. 523time.
398 524
399For interactive programs, values such as C<0.01> to C<0.1> should be fine. 525For interactive programs, values such as C<0.01> to C<0.1> should be fine.
400 526
401Example: Install an Event watcher that automatically calls 527Example: Install an EV watcher that automatically calls
402BDB::poll_cb with low priority, to ensure that other parts of the 528BDB::poll_cb with low priority, to ensure that other parts of the
403program get the CPU sometimes even under high AIO load. 529program get the CPU sometimes even under high load.
404 530
405 # try not to spend much more than 0.1s in poll_cb 531 # try not to spend much more than 0.1s in poll_cb
406 BDB::max_poll_time 0.1; 532 BDB::max_poll_time 0.1;
407 533
408 # use a low priority so other tasks have priority 534 my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
409 Event->io (fd => BDB::poll_fileno,
410 poll => 'r', nice => 1,
411 cb => &BDB::poll_cb);
412 535
413=item BDB::poll_wait 536=item BDB::poll_wait
414 537
415If there are any outstanding requests and none of them in the result 538If there are any outstanding requests and none of them in the result
416phase, wait till the result filehandle becomes ready for reading (simply 539phase, wait till the result filehandle becomes ready for reading (simply
… …
428 551
429 BDB::poll_wait, BDB::poll_cb 552 BDB::poll_wait, BDB::poll_cb
430 553
431=item BDB::flush 554=item BDB::flush
432 555
433Wait till all outstanding AIO requests have been handled. 556Wait till all outstanding BDB requests have been handled.
434 557
435Strictly equivalent to: 558Strictly equivalent to:
436 559
437 BDB::poll_wait, BDB::poll_cb 560 BDB::poll_wait, BDB::poll_cb
438 while BDB::nreqs; 561 while BDB::nreqs;
439 562
440=back 563=back
441 564
442=head3 CONTROLLING THE NUMBER OF THREADS 565=head2 VERSION CHECKING
566
567BerkeleyDB comes in various versions, many of them have minor
568incompatibilities. This means that traditional "at least version x.x"
569checks are often not sufficient.
570
571Example: set the log_autoremove option in a way compatible with <v4.7 and
572v4.7. Note the use of & on the constants to avoid triggering a compiletime
573bug when the symbol isn't available.
574
575 $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
576 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
443 577
444=over 4 578=over 4
445 579
580=item BDB::VERSION
581
582The C<BDB::VERSION> function, when called without arguments, returns the
583Berkeley DB version as a v-string (usually with 3 components). You should
584use C<lt> and C<ge> operators exclusively to make comparisons.
585
586Example: check for at least version 4.7.
587
588 BDB::VERSION ge v4.7 or die;
589
590=item BDB::VERSION min-version
591
592Returns true if the BDB version is at least the given version (specified
593as a v-string), false otherwise.
594
595Example: check for at least version 4.5.
596
597 BDB::VERSION v4.7 or die;
598
599=item BDB::VERSION min-version, max-version
600
601Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
602and less then C<max-version>.
603
604Example: check wether version is strictly less then v4.7.
605
606 BDB::VERSION v0, v4.7
607 or die "version 4.7 is not yet supported";
608
609=back
610
611=cut
612
613sub VERSION {
614 # I was dumb enough to override the VERSION method here, so let's try
615 # to fix it up.
616
617 if ($_[0] eq __PACKAGE__) {
618 $VERSION
619 } else {
620 if (@_ > 0) {
621 return undef if VERSION_v lt $_[0];
622 if (@_ > 1) {
623 return undef if VERSION_v ge $_[1];
624 }
625 }
626
627 VERSION_v
628 }
629}
630
631=head2 CONTROLLING THE NUMBER OF THREADS
632
633=over 4
634
446=item BDB::min_parallel $nthreads 635=item BDB::min_parallel $nthreads
447 636
448Set the minimum number of AIO threads to C<$nthreads>. The current 637Set the minimum number of BDB threads to C<$nthreads>. The current
449default is C<8>, which means eight asynchronous operations can execute 638default is C<8>, which means eight asynchronous operations can execute
450concurrently at any one time (the number of outstanding requests, 639concurrently at any one time (the number of outstanding requests,
451however, is unlimited). 640however, is unlimited).
452 641
453BDB starts threads only on demand, when an AIO request is queued and 642BDB starts threads only on demand, when an BDB request is queued and
454no free thread exists. Please note that queueing up a hundred requests can 643no free thread exists. Please note that queueing up a hundred requests can
455create demand for a hundred threads, even if it turns out that everything 644create demand for a hundred threads, even if it turns out that everything
456is in the cache and could have been processed faster by a single thread. 645is in the cache and could have been processed faster by a single thread.
457 646
458It is recommended to keep the number of threads relatively low, as some 647It is recommended to keep the number of threads relatively low, as some
… …
463Under most circumstances you don't need to call this function, as the 652Under most circumstances you don't need to call this function, as the
464module selects a default that is suitable for low to moderate load. 653module selects a default that is suitable for low to moderate load.
465 654
466=item BDB::max_parallel $nthreads 655=item BDB::max_parallel $nthreads
467 656
468Sets the maximum number of AIO threads to C<$nthreads>. If more than the 657Sets the maximum number of BDB threads to C<$nthreads>. If more than the
469specified number of threads are currently running, this function kills 658specified number of threads are currently running, this function kills
470them. This function blocks until the limit is reached. 659them. This function blocks until the limit is reached.
471 660
472While C<$nthreads> are zero, aio requests get queued but not executed 661While C<$nthreads> are zero, aio requests get queued but not executed
473until the number of threads has been increased again. 662until the number of threads has been increased again.
… …
508 697
509You can still queue as many requests as you want. Therefore, 698You can still queue as many requests as you want. Therefore,
510C<max_oustsanding> is mainly useful in simple scripts (with low values) or 699C<max_oustsanding> is mainly useful in simple scripts (with low values) or
511as a stop gap to shield against fatal memory overflow (with large values). 700as a stop gap to shield against fatal memory overflow (with large values).
512 701
513=item BDB::set_sync_prepare $cb 702=item $old_cb = BDB::set_sync_prepare $cb
514 703
515Sets a callback that is called whenever a request is created without an 704Sets a callback that is called whenever a request is created without an
516explicit callback. It has to return two code references. The first is used 705explicit callback. It has to return two code references. The first is used
517as the request callback, and the second is called to wait until the first 706as the request callback (it should save the return status), and the second
518callback has been called. The default implementation works like this: 707is called to wait until the first callback has been called (it must set
708C<$!> to the return status).
709
710This mechanism can be used to include BDB into other event mechanisms,
711such as L<Coro::BDB>.
712
713To allow other, callback-based, events to be executed while callback-less
714ones are run, you could use this sync prepare function:
519 715
520 sub { 716 sub {
521 my $status; 717 my $status;
522 ( 718 (
523 sub { $status = $! }, 719 sub { $status = $! },
524 sub { BDB::poll while !defined $status; $! = $status }, 720 sub { BDB::poll while !defined $status; $! = $status },
525 ) 721 )
526 } 722 }
527 723
724It works by polling for results till the request has finished and then
725sets C<$!> to the return value. This means that if you don't use a
726callback, BDB would simply fall back to synchronous operations.
727
728By default, or if the sync prepare function is set to C<undef>, is to
729execute callback-less BDB requests in the foreground thread, setting C<$!>
730to the return value, without polling for other events.
731
528=back 732=back
529 733
530=head3 STATISTICAL INFORMATION 734=head2 STATISTICAL INFORMATION
531 735
532=over 4 736=over 4
533 737
534=item BDB::nreqs 738=item BDB::nreqs
535 739
… …
553 757
554=back 758=back
555 759
556=cut 760=cut
557 761
558set_sync_prepare { 762set_sync_prepare (undef);
559 my $status;
560 (
561 sub {
562 $status = $!;
563 },
564 sub {
565 BDB::poll while !defined $status;
566 $! = $status;
567 },
568 )
569};
570 763
571min_parallel 8; 764min_parallel 8;
572 765
573END { flush } 766END { flush }
574 767
5751; 7681;
576 769
770=head1 COMMON PITFALLS
771
772=head2 Unexpected Crashes
773
774Remember that, by default, BDB will execute requests in parallel, in
775somewhat random order. That means that it is easy to run a C<db_get>
776request on thesa me database as a concurrent C<db_close> request, leading
777to a crash, silent data corruption, eventually the next world war on
778terrorism.
779
780If you only ever use foreground requests (without a callback), this will
781not be an issue.
782
783=head2 Unexpected Freezes or Deadlocks
784
785Remember that, by default, BDB will execute requests in parallel, which
786easily leads to deadlocks (even concurrent put's on the same database can
787deadlock).
788
789You either need to run deadlock detection (and handle the resulting
790errors), or make sure only one process ever updates the database, ine one
791thread, e.g. by using only foreground requests (without a callback).
792
577=head2 FORK BEHAVIOUR 793=head1 FORK BEHAVIOUR
578 794
579This module should do "the right thing" when the process using it forks: 795This module should do "the right thing" when the process using it forks:
580 796
581Before the fork, IO::AIO enters a quiescent state where no requests 797Before the fork, BDB enters a quiescent state where no requests
582can be added in other threads and no results will be processed. After 798can be added in other threads and no results will be processed. After
583the fork the parent simply leaves the quiescent state and continues 799the fork the parent simply leaves the quiescent state and continues
584request/result processing, while the child frees the request/result queue 800request/result processing, while the child frees the request/result queue
585(so that the requests started before the fork will only be handled in the 801(so that the requests started before the fork will only be handled in the
586parent). Threads will be started on demand until the limit set in the 802parent). Threads will be started on demand until the limit set in the
587parent process has been reached again. 803parent process has been reached again.
588 804
589In short: the parent will, after a short pause, continue as if fork had 805In short: the parent will, after a short pause, continue as if fork had
590not been called, while the child will act as if IO::AIO has not been used 806not been called, while the child will act as if BDB has not been used
591yet. 807yet.
592 808
809Win32 note: there is no fork on win32, and perls emulation of it is too
810broken to be supported, so do not use BDB in a windows pseudo-fork, better
811yet, switch to a more capable platform.
812
593=head2 MEMORY USAGE 813=head1 MEMORY USAGE
594 814
595Per-request usage: 815Per-request usage:
596 816
597Each aio request uses - depending on your architecture - around 100-200 817Each aio request uses - depending on your architecture - around 100-200
598bytes of memory. In addition, stat requests need a stat buffer (possibly 818bytes of memory. In addition, stat requests need a stat buffer (possibly
… …
607 827
608In the execution phase, some aio requests require more memory for 828In the execution phase, some aio requests require more memory for
609temporary buffers, and each thread requires a stack and other data 829temporary buffers, and each thread requires a stack and other data
610structures (usually around 16k-128k, depending on the OS). 830structures (usually around 16k-128k, depending on the OS).
611 831
832=head1 WIN32 FILENAMES/DATABASE NAME MESS
833
834Perl on Win32 supports only ASCII filenames (the reason is that it abuses
835an internal flag to store wether a filename is Unicode or ANSI, but that
836flag is used for somethign else in the perl core, so there is no way to
837detect wether a filename is ANSI or Unicode-encoded). The BDB module
838tries to work around this issue by assuming that the filename is an ANSI
839filename and BDB was built for unicode support.
840
612=head1 KNOWN BUGS 841=head1 KNOWN BUGS
613 842
614Known bugs will be fixed in the next release. 843Known bugs will be fixed in the next release, except:
844
845 If you use a transaction in any request, and the request returns
846 with an operating system error or DB_LOCK_NOTGRANTED, the internal
847 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
848 above.
615 849
616=head1 SEE ALSO 850=head1 SEE ALSO
617 851
618L<Coro::AIO>. 852L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
853syntax), L<IO::AIO> (nice to have).
619 854
620=head1 AUTHOR 855=head1 AUTHOR
621 856
622 Marc Lehmann <schmorp@schmorp.de> 857 Marc Lehmann <schmorp@schmorp.de>
623 http://home.schmorp.de/ 858 http://home.schmorp.de/

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