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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 1.70 by root, Thu Jan 18 16:45:27 2018 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 = '1.92';
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 db_env_lsn_reset db_env_fileid_reset
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)
208 db_env_lsn_reset (DB_ENV *env, bdb_filename db, U32 flags = 0, SV *callback = 0)
209 db_env_fileid_reset (DB_ENV *env, bdb_filename db, U32 flags = 0, SV *callback = 0)
142 210
143 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 211 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
144 flags: XA_CREATE 212 flags: XA_CREATE
145 213
146 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 214 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 215 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) 216 db_close (DB *db, U32 flags = 0, SV *callback = 0)
149 flags: DB_NOSYNC 217 flags: DB_NOSYNC
218 db_verify (DB *db, bdb_filename file, bdb_filename database = 0, SV *dummy = 0, U32 flags = 0, SV *callback = 0)
219 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) 220 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 221 flags: FREELIST_ONLY FREE_SPACE
152 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 222 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) 223 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) 224 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
155 flags: APPEND NODUPDATA NOOVERWRITE 225 flags: APPEND NODUPDATA NOOVERWRITE
226 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) 227 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 228 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) 229 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 230 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) 231 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) 232 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = 0)
162 flags: TXN_NOSYNC TXN_SYNC 233 flags: TXN_NOSYNC TXN_SYNC
163 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 234 db_txn_abort (DB_TXN *txn, SV *callback = 0)
164 235
165 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 236 db_c_close (DBC *dbc, SV *callback = 0)
166 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) 237 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) 238 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
168 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA 239 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) 240 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 241 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) 242 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) 243 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = 0)
173 244
174 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 245 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = 0)
175 flags: CREATE EXCL 246 flags: CREATE EXCL
176 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 247 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) 248 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 249 flags: TXN_NOSYNC
179 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 250 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = 0)
180 flags: TXN_NOSYNC 251 flags: TXN_NOSYNC
181 252
253=head3 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = 0)
254
255This is not actually a Berkeley DB function but a BDB module
256extension. The background for this exytension is: It is very annoying to
257have to check every single BDB function for error returns and provide a
258codepath out of your transaction. While the BDB module still makes this
259possible, it contains the following extensions:
260
261When a transaction-protected function returns any operating system
262error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
263transaction. This flag is also set by Berkeley DB functions themselves
264when an operation fails with LOCK_DEADLOCK, and it causes all further
265operations on that transaction (including C<db_txn_commit>) to fail.
266
267The C<db_txn_finish> request will look at this flag, and, if it is set,
268will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
269if it isn't set to something else yet). If it isn't set, it will call
270C<db_txn_commit> and return the error normally.
271
272How to use this? Easy: just write your transaction normally:
273
274 my $txn = $db_env->txn_begin;
275 db_get $db, $txn, "key", my $data;
276 db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
277 db_txn_finish $txn;
278 die "transaction failed" if $!;
279
280That is, handle only the expected errors. If something unexpected happens
281(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
282requests (db_put in this case) will simply be skipped (they will fail with
283LOCK_DEADLOCK) and the transaction will be aborted.
284
285You can use the C<< $txn->failed >> method to check wether a transaction
286has failed in this way and abort further processing (excluding
287C<db_txn_finish>).
288
289
182=head3 DB_ENV/database environment methods 290=head2 DB_ENV/database environment methods
183 291
184Methods available on DB_ENV/$env handles: 292Methods available on DB_ENV/$env handles:
185 293
186 DESTROY (DB_ENV_ornull *env) 294 DESTROY (DB_ENV_ornull *env)
187 CODE: 295 CODE:
… …
191 $int = $env->set_data_dir (const char *dir) 299 $int = $env->set_data_dir (const char *dir)
192 $int = $env->set_tmp_dir (const char *dir) 300 $int = $env->set_tmp_dir (const char *dir)
193 $int = $env->set_lg_dir (const char *dir) 301 $int = $env->set_lg_dir (const char *dir)
194 $int = $env->set_shm_key (long shm_key) 302 $int = $env->set_shm_key (long shm_key)
195 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 303 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
196 $int = $env->set_flags (U32 flags, int onoff) 304 $int = $env->set_flags (U32 flags, int onoff = 1)
305 $int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
306 $int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
197 $env->set_errfile (FILE *errfile = 0) 307 $env->set_errfile (FILE *errfile = 0)
198 $env->set_msgfile (FILE *msgfile = 0) 308 $env->set_msgfile (FILE *msgfile = 0)
199 $int = $env->set_verbose (U32 which, int onoff = 1) 309 $int = $env->set_verbose (U32 which, int onoff = 1)
200 $int = $env->set_encrypt (const char *password, U32 flags = 0) 310 $int = $env->set_encrypt (const char *password, U32 flags = 0)
201 $int = $env->set_timeout (NV timeout, U32 flags) 311 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
202 $int = $env->set_mp_max_openfd (int maxopenfd); 312 $int = $env->set_mp_max_openfd (int maxopenfd);
203 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); 313 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
204 $int = $env->set_mp_mmapsize (int mmapsize_mb) 314 $int = $env->set_mp_mmapsize (int mmapsize_mb)
205 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) 315 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
206 $int = $env->set_lk_max_lockers (U32 max) 316 $int = $env->set_lk_max_lockers (U32 max)
207 $int = $env->set_lk_max_locks (U32 max) 317 $int = $env->set_lk_max_locks (U32 max)
208 $int = $env->set_lk_max_objects (U32 max) 318 $int = $env->set_lk_max_objects (U32 max)
209 $int = $env->set_lg_bsize (U32 max) 319 $int = $env->set_lg_bsize (U32 max)
210 $int = $env->set_lg_max (U32 max) 320 $int = $env->set_lg_max (U32 max)
321 $int = $env->mutex_set_increment (U32 increment)
322 $int = $env->mutex_set_tas_spins (U32 tas_spins)
323 $int = $env->mutex_set_max (U32 max)
324 $int = $env->mutex_set_align (U32 align)
211 325
212 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 326 $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 327 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
328 $txn = $env->cdsgroup_begin; (v4.5)
214 329
215=head4 Example: 330=head3 Example:
216 331
217 use AnyEvent; 332 use AnyEvent;
218 use BDB; 333 use BDB;
219 334
220 our $FH; open $FH, "<&=" . BDB::poll_fileno; 335 our $FH; open $FH, "<&=" . BDB::poll_fileno;
… …
232 0600; 347 0600;
233 348
234 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 349 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
235 350
236 351
237=head3 DB/database methods 352=head2 DB/database methods
238 353
239Methods available on DB/$db handles: 354Methods available on DB/$db handles:
240 355
241 DESTROY (DB_ornull *db) 356 DESTROY (DB_ornull *db)
242 CODE: 357 CODE:
… …
268 383
269 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 384 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
270 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT 385 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
271 $seq = $db->sequence (U32 flags = 0) 386 $seq = $db->sequence (U32 flags = 0)
272 387
273=head4 Example: 388=head3 Example:
274 389
275 my $db = db_create $env; 390 my $db = db_create $env;
276 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600; 391 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600;
277 392
278 for (1..1000) { 393 for (1..1000) {
… …
285 db_del $db, undef, "key $_" for 1..1000; 400 db_del $db, undef, "key $_" for 1..1000;
286 401
287 db_sync $db; 402 db_sync $db;
288 403
289 404
290=head3 DB_TXN/transaction methods 405=head2 DB_TXN/transaction methods
291 406
292Methods available on DB_TXN/$txn handles: 407Methods available on DB_TXN/$txn handles:
293 408
294 DESTROY (DB_TXN_ornull *txn) 409 DESTROY (DB_TXN_ornull *txn)
295 CODE: 410 CODE:
296 if (txn) 411 if (txn)
297 txn->abort (txn); 412 txn->abort (txn);
298 413
299 $int = $txn->set_timeout (NV timeout, U32 flags) 414 $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
300 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT 415 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
301 416
417 $bool = $txn->failed
418 # see db_txn_finish documentation, above
302 419
420
303=head3 DBC/cursor methods 421=head2 DBC/cursor methods
304 422
305Methods available on DBC/$dbc handles: 423Methods available on DBC/$dbc handles:
306 424
307 DESTROY (DBC_ornull *dbc) 425 DESTROY (DBC_ornull *dbc)
308 CODE: 426 CODE:
309 if (dbc) 427 if (dbc)
310 dbc->c_close (dbc); 428 dbc->c_close (dbc);
311 429
430 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
431
312=head4 Example: 432=head3 Example:
313 433
314 my $c = $db->cursor; 434 my $c = $db->cursor;
315 435
316 for (;;) { 436 for (;;) {
317 db_c_get $c, my $key, my $data, BDB::NEXT; 437 db_c_get $c, my $key, my $data, BDB::NEXT;
… …
320 } 440 }
321 441
322 db_c_close $c; 442 db_c_close $c;
323 443
324 444
325=head3 DB_SEQUENCE/sequence methods 445=head2 DB_SEQUENCE/sequence methods
326 446
327Methods available on DB_SEQUENCE/$seq handles: 447Methods available on DB_SEQUENCE/$seq handles:
328 448
329 DESTROY (DB_SEQUENCE_ornull *seq) 449 DESTROY (DB_SEQUENCE_ornull *seq)
330 CODE: 450 CODE:
… …
335 $int = $seq->set_cachesize (U32 size) 455 $int = $seq->set_cachesize (U32 size)
336 $int = $seq->set_flags (U32 flags) 456 $int = $seq->set_flags (U32 flags)
337 flags: SEQ_DEC SEQ_INC SEQ_WRAP 457 flags: SEQ_DEC SEQ_INC SEQ_WRAP
338 $int = $seq->set_range (db_seq_t min, db_seq_t max) 458 $int = $seq->set_range (db_seq_t min, db_seq_t max)
339 459
340=head4 Example: 460=head3 Example:
341 461
342 my $seq = $db->sequence; 462 my $seq = $db->sequence;
343 463
344 db_sequence_open $seq, undef, "seq", BDB::CREATE; 464 db_sequence_open $seq, undef, "seq", BDB::CREATE;
345 db_sequence_get $seq, undef, 1, my $value; 465 db_sequence_get $seq, undef, 1, my $value;
346 466
347 467
348=head2 SUPPORT FUNCTIONS 468=head1 SUPPORT FUNCTIONS
349 469
350=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 470=head2 EVENT PROCESSING AND EVENT LOOP INTEGRATION
351 471
352=over 4 472=over 4
473
474=item $msg = BDB::strerror [$errno]
475
476Returns the string corresponding to the given errno value. If no argument
477is given, use C<$!>.
478
479Note that the BDB module also patches the C<$!> variable directly, so you
480should be able to get a bdb error string by simply stringifying C<$!>.
353 481
354=item $fileno = BDB::poll_fileno 482=item $fileno = BDB::poll_fileno
355 483
356Return the I<request result pipe file descriptor>. This filehandle must be 484Return the I<request result pipe file descriptor>. This filehandle must be
357polled for reading by some mechanism outside this module (e.g. Event or 485polled for reading by some mechanism outside this module (e.g. Event or
… …
396interactiveness when perl is not fast enough to process all requests in 524interactiveness when perl is not fast enough to process all requests in
397time. 525time.
398 526
399For interactive programs, values such as C<0.01> to C<0.1> should be fine. 527For interactive programs, values such as C<0.01> to C<0.1> should be fine.
400 528
401Example: Install an Event watcher that automatically calls 529Example: Install an EV watcher that automatically calls
402BDB::poll_cb with low priority, to ensure that other parts of the 530BDB::poll_cb with low priority, to ensure that other parts of the
403program get the CPU sometimes even under high AIO load. 531program get the CPU sometimes even under high load.
404 532
405 # try not to spend much more than 0.1s in poll_cb 533 # try not to spend much more than 0.1s in poll_cb
406 BDB::max_poll_time 0.1; 534 BDB::max_poll_time 0.1;
407 535
408 # use a low priority so other tasks have priority 536 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);
412 537
413=item BDB::poll_wait 538=item BDB::poll_wait
414 539
415If there are any outstanding requests and none of them in the result 540If there are any outstanding requests and none of them in the result
416phase, wait till the result filehandle becomes ready for reading (simply 541phase, wait till the result filehandle becomes ready for reading (simply
… …
428 553
429 BDB::poll_wait, BDB::poll_cb 554 BDB::poll_wait, BDB::poll_cb
430 555
431=item BDB::flush 556=item BDB::flush
432 557
433Wait till all outstanding AIO requests have been handled. 558Wait till all outstanding BDB requests have been handled.
434 559
435Strictly equivalent to: 560Strictly equivalent to:
436 561
437 BDB::poll_wait, BDB::poll_cb 562 BDB::poll_wait, BDB::poll_cb
438 while BDB::nreqs; 563 while BDB::nreqs;
439 564
440=back 565=back
441 566
442=head3 CONTROLLING THE NUMBER OF THREADS 567=head2 VERSION CHECKING
568
569BerkeleyDB comes in various versions, many of them have minor
570incompatibilities. This means that traditional "at least version x.x"
571checks are often not sufficient.
572
573Example: set the log_autoremove option in a way compatible with <v4.7 and
574v4.7. Note the use of & on the constants to avoid triggering a compiletime
575bug when the symbol isn't available.
576
577 $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
578 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
443 579
444=over 4 580=over 4
445 581
582=item BDB::VERSION
583
584The C<BDB::VERSION> function, when called without arguments, returns the
585Berkeley DB version as a v-string (usually with 3 components). You should
586use C<lt> and C<ge> operators exclusively to make comparisons.
587
588Example: check for at least version 4.7.
589
590 BDB::VERSION ge v4.7 or die;
591
592=item BDB::VERSION min-version
593
594Returns true if the BDB version is at least the given version (specified
595as a v-string), false otherwise.
596
597Example: check for at least version 4.5.
598
599 BDB::VERSION v4.7 or die;
600
601=item BDB::VERSION min-version, max-version
602
603Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
604and less then C<max-version>.
605
606Example: check wether version is strictly less then v4.7.
607
608 BDB::VERSION v0, v4.7
609 or die "version 4.7 is not yet supported";
610
611=back
612
613=cut
614
615sub VERSION {
616 # I was dumb enough to override the VERSION method here, so let's try
617 # to fix it up.
618
619 if ($_[0] eq __PACKAGE__) {
620 $VERSION
621 } else {
622 if (@_ > 0) {
623 return undef if VERSION_v lt $_[0];
624 if (@_ > 1) {
625 return undef if VERSION_v ge $_[1];
626 }
627 }
628
629 VERSION_v
630 }
631}
632
633=head2 CONTROLLING THE NUMBER OF THREADS
634
635=over 4
636
446=item BDB::min_parallel $nthreads 637=item BDB::min_parallel $nthreads
447 638
448Set the minimum number of AIO threads to C<$nthreads>. The current 639Set the minimum number of BDB threads to C<$nthreads>. The current
449default is C<8>, which means eight asynchronous operations can execute 640default is C<8>, which means eight asynchronous operations can execute
450concurrently at any one time (the number of outstanding requests, 641concurrently at any one time (the number of outstanding requests,
451however, is unlimited). 642however, is unlimited).
452 643
453BDB starts threads only on demand, when an AIO request is queued and 644BDB 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 645no 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 646create 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. 647is in the cache and could have been processed faster by a single thread.
457 648
458It is recommended to keep the number of threads relatively low, as some 649It 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 654Under most circumstances you don't need to call this function, as the
464module selects a default that is suitable for low to moderate load. 655module selects a default that is suitable for low to moderate load.
465 656
466=item BDB::max_parallel $nthreads 657=item BDB::max_parallel $nthreads
467 658
468Sets the maximum number of AIO threads to C<$nthreads>. If more than the 659Sets the maximum number of BDB threads to C<$nthreads>. If more than the
469specified number of threads are currently running, this function kills 660specified number of threads are currently running, this function kills
470them. This function blocks until the limit is reached. 661them. This function blocks until the limit is reached.
471 662
472While C<$nthreads> are zero, aio requests get queued but not executed 663While C<$nthreads> are zero, aio requests get queued but not executed
473until the number of threads has been increased again. 664until the number of threads has been increased again.
… …
508 699
509You can still queue as many requests as you want. Therefore, 700You can still queue as many requests as you want. Therefore,
510C<max_oustsanding> is mainly useful in simple scripts (with low values) or 701C<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). 702as a stop gap to shield against fatal memory overflow (with large values).
512 703
513=item BDB::set_sync_prepare $cb 704=item $old_cb = BDB::set_sync_prepare $cb
514 705
515Sets a callback that is called whenever a request is created without an 706Sets a callback that is called whenever a request is created without an
516explicit callback. It has to return two code references. The first is used 707explicit callback. It has to return two code references. The first is used
517as the request callback, and the second is called to wait until the first 708as the request callback (it should save the return status), and the second
518callback has been called. The default implementation works like this: 709is called to wait until the first callback has been called (it must set
710C<$!> to the return status).
711
712This mechanism can be used to include BDB into other event mechanisms,
713such as L<Coro::BDB>.
714
715To allow other, callback-based, events to be executed while callback-less
716ones are run, you could use this sync prepare function:
519 717
520 sub { 718 sub {
521 my $status; 719 my $status;
522 ( 720 (
523 sub { $status = $! }, 721 sub { $status = $! },
524 sub { BDB::poll while !defined $status; $! = $status }, 722 sub { BDB::poll while !defined $status; $! = $status },
525 ) 723 )
526 } 724 }
527 725
726It works by polling for results till the request has finished and then
727sets C<$!> to the return value. This means that if you don't use a
728callback, BDB would simply fall back to synchronous operations.
729
730By default, or if the sync prepare function is set to C<undef>, is to
731execute callback-less BDB requests in the foreground thread, setting C<$!>
732to the return value, without polling for other events.
733
528=back 734=back
529 735
530=head3 STATISTICAL INFORMATION 736=head2 STATISTICAL INFORMATION
531 737
532=over 4 738=over 4
533 739
534=item BDB::nreqs 740=item BDB::nreqs
535 741
… …
553 759
554=back 760=back
555 761
556=cut 762=cut
557 763
558set_sync_prepare { 764set_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};
570 765
571min_parallel 8; 766min_parallel 8;
572 767
573END { flush } 768END { flush }
574 769
5751; 7701;
576 771
772=head1 COMMON PITFALLS
773
774=head2 Unexpected Crashes
775
776Remember that, by default, BDB will execute requests in parallel, in
777somewhat random order. That means that it is easy to run a C<db_get>
778request on the same database as a concurrent C<db_close> request, leading
779to a crash, silent data corruption, eventually the next world war on
780terrorism.
781
782If you only ever use foreground requests (without a callback), this will
783not be an issue (unless you use threads).
784
785=head2 Unexpected Freezes or Deadlocks
786
787Remember that, by default, BDB will execute requests in parallel, which
788easily leads to deadlocks (even concurrent put's on the same database can
789deadlock).
790
791You either need to run deadlock detection (and handle the resulting
792errors), or make sure only one process ever updates the database, ine one
793thread, e.g. by using only foreground requests (without a callback).
794
577=head2 FORK BEHAVIOUR 795=head1 FORK BEHAVIOUR
578 796
579This module should do "the right thing" when the process using it forks: 797This module should do "the right thing" when the process using it forks:
580 798
581Before the fork, IO::AIO enters a quiescent state where no requests 799Before the fork, BDB enters a quiescent state where no requests
582can be added in other threads and no results will be processed. After 800can be added in other threads and no results will be processed. After
583the fork the parent simply leaves the quiescent state and continues 801the fork the parent simply leaves the quiescent state and continues
584request/result processing, while the child frees the request/result queue 802request/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 803(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 804parent). Threads will be started on demand until the limit set in the
587parent process has been reached again. 805parent process has been reached again.
588 806
589In short: the parent will, after a short pause, continue as if fork had 807In 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 808not been called, while the child will act as if BDB has not been used
591yet. 809yet.
592 810
811Win32 note: there is no fork on win32, and perls emulation of it is too
812broken to be supported, so do not use BDB in a windows pseudo-fork, better
813yet, switch to a more capable platform.
814
593=head2 MEMORY USAGE 815=head1 MEMORY USAGE
594 816
595Per-request usage: 817Per-request usage:
596 818
597Each aio request uses - depending on your architecture - around 100-200 819Each aio request uses - depending on your architecture - around 100-200
598bytes of memory. In addition, stat requests need a stat buffer (possibly 820bytes of memory. In addition, stat requests need a stat buffer (possibly
… …
607 829
608In the execution phase, some aio requests require more memory for 830In the execution phase, some aio requests require more memory for
609temporary buffers, and each thread requires a stack and other data 831temporary buffers, and each thread requires a stack and other data
610structures (usually around 16k-128k, depending on the OS). 832structures (usually around 16k-128k, depending on the OS).
611 833
834=head1 WIN32 FILENAMES/DATABASE NAME MESS
835
836Perl on Win32 supports only ASCII filenames (the reason is that it abuses
837an internal flag to store wether a filename is Unicode or ANSI, but that
838flag is used for somethign else in the perl core, so there is no way to
839detect wether a filename is ANSI or Unicode-encoded). The BDB module
840tries to work around this issue by assuming that the filename is an ANSI
841filename and BDB was built for unicode support.
842
612=head1 KNOWN BUGS 843=head1 KNOWN BUGS
613 844
614Known bugs will be fixed in the next release. 845Known bugs will be fixed in the next release, except:
846
847 If you use a transaction in any request, and the request returns
848 with an operating system error or DB_LOCK_NOTGRANTED, the internal
849 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
850 above.
615 851
616=head1 SEE ALSO 852=head1 SEE ALSO
617 853
618L<Coro::AIO>. 854L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
855syntax), L<IO::AIO> (nice to have).
619 856
620=head1 AUTHOR 857=head1 AUTHOR
621 858
622 Marc Lehmann <schmorp@schmorp.de> 859 Marc Lehmann <schmorp@schmorp.de>
623 http://home.schmorp.de/ 860 http://home.schmorp.de/

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