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Comparing BDB/BDB.pm (file contents):
Revision 1.15 by root, Thu Sep 13 21:34:00 2007 UTC vs.
Revision 1.67 by root, Tue Feb 2 04:07:06 2016 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 = '1.1'; 115 $VERSION = '1.91';
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_reset_lsn
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 db_txn_finish 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 );
… …
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)
142 209
143 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 210 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
144 flags: XA_CREATE 211 flags: XA_CREATE
145 212
146 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 213 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 214 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) 215 db_close (DB *db, U32 flags = 0, SV *callback = 0)
149 flags: DB_NOSYNC 216 flags: DB_NOSYNC
217 db_verify (DB *db, bdb_filename file, bdb_filename database = 0, SV *dummy = 0, U32 flags = 0, SV *callback = 0)
218 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) 219 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 220 flags: FREELIST_ONLY FREE_SPACE
152 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 221 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) 222 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) 223 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
155 flags: APPEND NODUPDATA NOOVERWRITE 224 flags: APPEND NODUPDATA NOOVERWRITE
225 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) 226 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 227 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) 228 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 229 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) 230 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) 231 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = 0)
162 flags: TXN_NOSYNC TXN_SYNC 232 flags: TXN_NOSYNC TXN_SYNC
163 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 233 db_txn_abort (DB_TXN *txn, SV *callback = 0)
164 234
165 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 235 db_c_close (DBC *dbc, SV *callback = 0)
166 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) 236 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) 237 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = 0)
168 flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA 238 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) 239 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 240 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) 241 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) 242 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = 0)
173 243
174 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 244 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = 0)
175 flags: CREATE EXCL 245 flags: CREATE EXCL
176 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 246 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) 247 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 248 flags: TXN_NOSYNC
179 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 249 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = 0)
180 flags: TXN_NOSYNC 250 flags: TXN_NOSYNC
181 251
182=head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) 252=head3 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = 0)
183 253
184This is not a Berkeley DB function but a BDB module extension. It is very 254This is not actually a Berkeley DB function but a BDB module
255extension. The background for this exytension is: It is very annoying to
185annoying to have to check every single BDB function for error returns and 256have to check every single BDB function for error returns and provide a
186provide a codepath out of your transaction. While the BDB module still 257codepath out of your transaction. While the BDB module still makes this
187makes this possible, it contains the following extensions: 258possible, it contains the following extensions:
188 259
189When a transaction-protected function returns any operating system 260When a transaction-protected function returns any operating system
190error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the 261error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
191transaction. This flag is also set by Berkeley DB functions externally 262transaction. This flag is also set by Berkeley DB functions themselves
192when an operation fails with LOCK_DEADLOCK, and it causes all further 263when an operation fails with LOCK_DEADLOCK, and it causes all further
193operations on that transaction (including C<db_txn_commit>) to fail. 264operations on that transaction (including C<db_txn_commit>) to fail.
194 265
195The C<db_txn_finish> request will look at this flag, and, if it is set, 266The C<db_txn_finish> request will look at this flag, and, if it is set,
196will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK> 267will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
197if it isn't set). If it isn't set, it will call C<db_txn_commit> and 268if it isn't set to something else yet). If it isn't set, it will call
198return the error normally. 269C<db_txn_commit> and return the error normally.
199 270
200How to use this? Easy: just write your transaction normally: 271How to use this? Easy: just write your transaction normally:
201 272
202 my $txn = $db_env->txn_begin; 273 my $txn = $db_env->txn_begin;
203 db_get $db, $txn, "key", my $data; 274 db_get $db, $txn, "key", my $data;
… …
208That is, handle only the expected errors. If something unexpected happens 279That is, handle only the expected errors. If something unexpected happens
209(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining 280(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
210requests (db_put in this case) will simply be skipped (they will fail with 281requests (db_put in this case) will simply be skipped (they will fail with
211LOCK_DEADLOCK) and the transaction will be aborted. 282LOCK_DEADLOCK) and the transaction will be aborted.
212 283
213You cna use the C<< $txn->failed >> method to check wether a transaction 284You can use the C<< $txn->failed >> method to check wether a transaction
214has failed in this way and abort further processing (excluding 285has failed in this way and abort further processing (excluding
215C<db_txn_finish>). 286C<db_txn_finish>).
216 287
288
217=head3 DB_ENV/database environment methods 289=head2 DB_ENV/database environment methods
218 290
219Methods available on DB_ENV/$env handles: 291Methods available on DB_ENV/$env handles:
220 292
221 DESTROY (DB_ENV_ornull *env) 293 DESTROY (DB_ENV_ornull *env)
222 CODE: 294 CODE:
… …
226 $int = $env->set_data_dir (const char *dir) 298 $int = $env->set_data_dir (const char *dir)
227 $int = $env->set_tmp_dir (const char *dir) 299 $int = $env->set_tmp_dir (const char *dir)
228 $int = $env->set_lg_dir (const char *dir) 300 $int = $env->set_lg_dir (const char *dir)
229 $int = $env->set_shm_key (long shm_key) 301 $int = $env->set_shm_key (long shm_key)
230 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 302 $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
231 $int = $env->set_flags (U32 flags, int onoff) 303 $int = $env->set_flags (U32 flags, int onoff = 1)
304 $int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
305 $int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
232 $env->set_errfile (FILE *errfile = 0) 306 $env->set_errfile (FILE *errfile = 0)
233 $env->set_msgfile (FILE *msgfile = 0) 307 $env->set_msgfile (FILE *msgfile = 0)
234 $int = $env->set_verbose (U32 which, int onoff = 1) 308 $int = $env->set_verbose (U32 which, int onoff = 1)
235 $int = $env->set_encrypt (const char *password, U32 flags = 0) 309 $int = $env->set_encrypt (const char *password, U32 flags = 0)
236 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) 310 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
… …
241 $int = $env->set_lk_max_lockers (U32 max) 315 $int = $env->set_lk_max_lockers (U32 max)
242 $int = $env->set_lk_max_locks (U32 max) 316 $int = $env->set_lk_max_locks (U32 max)
243 $int = $env->set_lk_max_objects (U32 max) 317 $int = $env->set_lk_max_objects (U32 max)
244 $int = $env->set_lg_bsize (U32 max) 318 $int = $env->set_lg_bsize (U32 max)
245 $int = $env->set_lg_max (U32 max) 319 $int = $env->set_lg_max (U32 max)
320 $int = $env->mutex_set_increment (U32 increment)
321 $int = $env->mutex_set_tas_spins (U32 tas_spins)
322 $int = $env->mutex_set_max (U32 max)
323 $int = $env->mutex_set_align (U32 align)
246 324
247 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 325 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
248 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC 326 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
327 $txn = $env->cdsgroup_begin; (v4.5)
249 328
250=head4 Example: 329=head3 Example:
251 330
252 use AnyEvent; 331 use AnyEvent;
253 use BDB; 332 use BDB;
254 333
255 our $FH; open $FH, "<&=" . BDB::poll_fileno; 334 our $FH; open $FH, "<&=" . BDB::poll_fileno;
… …
267 0600; 346 0600;
268 347
269 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); 348 $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1);
270 349
271 350
272=head3 DB/database methods 351=head2 DB/database methods
273 352
274Methods available on DB/$db handles: 353Methods available on DB/$db handles:
275 354
276 DESTROY (DB_ornull *db) 355 DESTROY (DB_ornull *db)
277 CODE: 356 CODE:
… …
303 382
304 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 383 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
305 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT 384 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
306 $seq = $db->sequence (U32 flags = 0) 385 $seq = $db->sequence (U32 flags = 0)
307 386
308=head4 Example: 387=head3 Example:
309 388
310 my $db = db_create $env; 389 my $db = db_create $env;
311 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600; 390 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600;
312 391
313 for (1..1000) { 392 for (1..1000) {
… …
320 db_del $db, undef, "key $_" for 1..1000; 399 db_del $db, undef, "key $_" for 1..1000;
321 400
322 db_sync $db; 401 db_sync $db;
323 402
324 403
325=head3 DB_TXN/transaction methods 404=head2 DB_TXN/transaction methods
326 405
327Methods available on DB_TXN/$txn handles: 406Methods available on DB_TXN/$txn handles:
328 407
329 DESTROY (DB_TXN_ornull *txn) 408 DESTROY (DB_TXN_ornull *txn)
330 CODE: 409 CODE:
… …
336 415
337 $bool = $txn->failed 416 $bool = $txn->failed
338 # see db_txn_finish documentation, above 417 # see db_txn_finish documentation, above
339 418
340 419
341=head3 DBC/cursor methods 420=head2 DBC/cursor methods
342 421
343Methods available on DBC/$dbc handles: 422Methods available on DBC/$dbc handles:
344 423
345 DESTROY (DBC_ornull *dbc) 424 DESTROY (DBC_ornull *dbc)
346 CODE: 425 CODE:
347 if (dbc) 426 if (dbc)
348 dbc->c_close (dbc); 427 dbc->c_close (dbc);
349 428
429 $int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
430
350=head4 Example: 431=head3 Example:
351 432
352 my $c = $db->cursor; 433 my $c = $db->cursor;
353 434
354 for (;;) { 435 for (;;) {
355 db_c_get $c, my $key, my $data, BDB::NEXT; 436 db_c_get $c, my $key, my $data, BDB::NEXT;
… …
358 } 439 }
359 440
360 db_c_close $c; 441 db_c_close $c;
361 442
362 443
363=head3 DB_SEQUENCE/sequence methods 444=head2 DB_SEQUENCE/sequence methods
364 445
365Methods available on DB_SEQUENCE/$seq handles: 446Methods available on DB_SEQUENCE/$seq handles:
366 447
367 DESTROY (DB_SEQUENCE_ornull *seq) 448 DESTROY (DB_SEQUENCE_ornull *seq)
368 CODE: 449 CODE:
… …
373 $int = $seq->set_cachesize (U32 size) 454 $int = $seq->set_cachesize (U32 size)
374 $int = $seq->set_flags (U32 flags) 455 $int = $seq->set_flags (U32 flags)
375 flags: SEQ_DEC SEQ_INC SEQ_WRAP 456 flags: SEQ_DEC SEQ_INC SEQ_WRAP
376 $int = $seq->set_range (db_seq_t min, db_seq_t max) 457 $int = $seq->set_range (db_seq_t min, db_seq_t max)
377 458
378=head4 Example: 459=head3 Example:
379 460
380 my $seq = $db->sequence; 461 my $seq = $db->sequence;
381 462
382 db_sequence_open $seq, undef, "seq", BDB::CREATE; 463 db_sequence_open $seq, undef, "seq", BDB::CREATE;
383 db_sequence_get $seq, undef, 1, my $value; 464 db_sequence_get $seq, undef, 1, my $value;
384 465
385 466
386=head2 SUPPORT FUNCTIONS 467=head1 SUPPORT FUNCTIONS
387 468
388=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 469=head2 EVENT PROCESSING AND EVENT LOOP INTEGRATION
389 470
390=over 4 471=over 4
472
473=item $msg = BDB::strerror [$errno]
474
475Returns the string corresponding to the given errno value. If no argument
476is given, use C<$!>.
477
478Note that the BDB module also patches the C<$!> variable directly, so you
479should be able to get a bdb error string by simply stringifying C<$!>.
391 480
392=item $fileno = BDB::poll_fileno 481=item $fileno = BDB::poll_fileno
393 482
394Return the I<request result pipe file descriptor>. This filehandle must be 483Return the I<request result pipe file descriptor>. This filehandle must be
395polled for reading by some mechanism outside this module (e.g. Event or 484polled for reading by some mechanism outside this module (e.g. Event or
… …
434interactiveness when perl is not fast enough to process all requests in 523interactiveness when perl is not fast enough to process all requests in
435time. 524time.
436 525
437For interactive programs, values such as C<0.01> to C<0.1> should be fine. 526For interactive programs, values such as C<0.01> to C<0.1> should be fine.
438 527
439Example: Install an Event watcher that automatically calls 528Example: Install an EV watcher that automatically calls
440BDB::poll_cb with low priority, to ensure that other parts of the 529BDB::poll_cb with low priority, to ensure that other parts of the
441program get the CPU sometimes even under high AIO load. 530program get the CPU sometimes even under high load.
442 531
443 # try not to spend much more than 0.1s in poll_cb 532 # try not to spend much more than 0.1s in poll_cb
444 BDB::max_poll_time 0.1; 533 BDB::max_poll_time 0.1;
445 534
446 # use a low priority so other tasks have priority 535 my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
447 Event->io (fd => BDB::poll_fileno,
448 poll => 'r', nice => 1,
449 cb => &BDB::poll_cb);
450 536
451=item BDB::poll_wait 537=item BDB::poll_wait
452 538
453If there are any outstanding requests and none of them in the result 539If there are any outstanding requests and none of them in the result
454phase, wait till the result filehandle becomes ready for reading (simply 540phase, wait till the result filehandle becomes ready for reading (simply
… …
466 552
467 BDB::poll_wait, BDB::poll_cb 553 BDB::poll_wait, BDB::poll_cb
468 554
469=item BDB::flush 555=item BDB::flush
470 556
471Wait till all outstanding AIO requests have been handled. 557Wait till all outstanding BDB requests have been handled.
472 558
473Strictly equivalent to: 559Strictly equivalent to:
474 560
475 BDB::poll_wait, BDB::poll_cb 561 BDB::poll_wait, BDB::poll_cb
476 while BDB::nreqs; 562 while BDB::nreqs;
477 563
478=back 564=back
479 565
480=head3 CONTROLLING THE NUMBER OF THREADS 566=head2 VERSION CHECKING
567
568BerkeleyDB comes in various versions, many of them have minor
569incompatibilities. This means that traditional "at least version x.x"
570checks are often not sufficient.
571
572Example: set the log_autoremove option in a way compatible with <v4.7 and
573v4.7. Note the use of & on the constants to avoid triggering a compiletime
574bug when the symbol isn't available.
575
576 $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
577 $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
481 578
482=over 4 579=over 4
483 580
581=item BDB::VERSION
582
583The C<BDB::VERSION> function, when called without arguments, returns the
584Berkeley DB version as a v-string (usually with 3 components). You should
585use C<lt> and C<ge> operators exclusively to make comparisons.
586
587Example: check for at least version 4.7.
588
589 BDB::VERSION ge v4.7 or die;
590
591=item BDB::VERSION min-version
592
593Returns true if the BDB version is at least the given version (specified
594as a v-string), false otherwise.
595
596Example: check for at least version 4.5.
597
598 BDB::VERSION v4.7 or die;
599
600=item BDB::VERSION min-version, max-version
601
602Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
603and less then C<max-version>.
604
605Example: check wether version is strictly less then v4.7.
606
607 BDB::VERSION v0, v4.7
608 or die "version 4.7 is not yet supported";
609
610=back
611
612=cut
613
614sub VERSION {
615 # I was dumb enough to override the VERSION method here, so let's try
616 # to fix it up.
617
618 if ($_[0] eq __PACKAGE__) {
619 $VERSION
620 } else {
621 if (@_ > 0) {
622 return undef if VERSION_v lt $_[0];
623 if (@_ > 1) {
624 return undef if VERSION_v ge $_[1];
625 }
626 }
627
628 VERSION_v
629 }
630}
631
632=head2 CONTROLLING THE NUMBER OF THREADS
633
634=over 4
635
484=item BDB::min_parallel $nthreads 636=item BDB::min_parallel $nthreads
485 637
486Set the minimum number of AIO threads to C<$nthreads>. The current 638Set the minimum number of BDB threads to C<$nthreads>. The current
487default is C<8>, which means eight asynchronous operations can execute 639default is C<8>, which means eight asynchronous operations can execute
488concurrently at any one time (the number of outstanding requests, 640concurrently at any one time (the number of outstanding requests,
489however, is unlimited). 641however, is unlimited).
490 642
491BDB starts threads only on demand, when an AIO request is queued and 643BDB starts threads only on demand, when an BDB request is queued and
492no free thread exists. Please note that queueing up a hundred requests can 644no free thread exists. Please note that queueing up a hundred requests can
493create demand for a hundred threads, even if it turns out that everything 645create demand for a hundred threads, even if it turns out that everything
494is in the cache and could have been processed faster by a single thread. 646is in the cache and could have been processed faster by a single thread.
495 647
496It is recommended to keep the number of threads relatively low, as some 648It is recommended to keep the number of threads relatively low, as some
… …
501Under most circumstances you don't need to call this function, as the 653Under most circumstances you don't need to call this function, as the
502module selects a default that is suitable for low to moderate load. 654module selects a default that is suitable for low to moderate load.
503 655
504=item BDB::max_parallel $nthreads 656=item BDB::max_parallel $nthreads
505 657
506Sets the maximum number of AIO threads to C<$nthreads>. If more than the 658Sets the maximum number of BDB threads to C<$nthreads>. If more than the
507specified number of threads are currently running, this function kills 659specified number of threads are currently running, this function kills
508them. This function blocks until the limit is reached. 660them. This function blocks until the limit is reached.
509 661
510While C<$nthreads> are zero, aio requests get queued but not executed 662While C<$nthreads> are zero, aio requests get queued but not executed
511until the number of threads has been increased again. 663until the number of threads has been increased again.
… …
546 698
547You can still queue as many requests as you want. Therefore, 699You can still queue as many requests as you want. Therefore,
548C<max_oustsanding> is mainly useful in simple scripts (with low values) or 700C<max_oustsanding> is mainly useful in simple scripts (with low values) or
549as a stop gap to shield against fatal memory overflow (with large values). 701as a stop gap to shield against fatal memory overflow (with large values).
550 702
551=item BDB::set_sync_prepare $cb 703=item $old_cb = BDB::set_sync_prepare $cb
552 704
553Sets a callback that is called whenever a request is created without an 705Sets a callback that is called whenever a request is created without an
554explicit callback. It has to return two code references. The first is used 706explicit callback. It has to return two code references. The first is used
555as the request callback, and the second is called to wait until the first 707as the request callback (it should save the return status), and the second
556callback has been called. The default implementation works like this: 708is called to wait until the first callback has been called (it must set
709C<$!> to the return status).
710
711This mechanism can be used to include BDB into other event mechanisms,
712such as L<Coro::BDB>.
713
714To allow other, callback-based, events to be executed while callback-less
715ones are run, you could use this sync prepare function:
557 716
558 sub { 717 sub {
559 my $status; 718 my $status;
560 ( 719 (
561 sub { $status = $! }, 720 sub { $status = $! },
562 sub { BDB::poll while !defined $status; $! = $status }, 721 sub { BDB::poll while !defined $status; $! = $status },
563 ) 722 )
564 } 723 }
565 724
725It works by polling for results till the request has finished and then
726sets C<$!> to the return value. This means that if you don't use a
727callback, BDB would simply fall back to synchronous operations.
728
729By default, or if the sync prepare function is set to C<undef>, is to
730execute callback-less BDB requests in the foreground thread, setting C<$!>
731to the return value, without polling for other events.
732
566=back 733=back
567 734
568=head3 STATISTICAL INFORMATION 735=head2 STATISTICAL INFORMATION
569 736
570=over 4 737=over 4
571 738
572=item BDB::nreqs 739=item BDB::nreqs
573 740
… …
591 758
592=back 759=back
593 760
594=cut 761=cut
595 762
596set_sync_prepare { 763set_sync_prepare (undef);
597 my $status;
598 (
599 sub {
600 $status = $!;
601 },
602 sub {
603 BDB::poll while !defined $status;
604 $! = $status;
605 },
606 )
607};
608 764
609min_parallel 8; 765min_parallel 8;
610 766
611END { flush } 767END { flush }
612 768
6131; 7691;
614 770
771=head1 COMMON PITFALLS
772
773=head2 Unexpected Crashes
774
775Remember that, by default, BDB will execute requests in parallel, in
776somewhat random order. That means that it is easy to run a C<db_get>
777request on the same database as a concurrent C<db_close> request, leading
778to a crash, silent data corruption, eventually the next world war on
779terrorism.
780
781If you only ever use foreground requests (without a callback), this will
782not be an issue (unless you use threads).
783
784=head2 Unexpected Freezes or Deadlocks
785
786Remember that, by default, BDB will execute requests in parallel, which
787easily leads to deadlocks (even concurrent put's on the same database can
788deadlock).
789
790You either need to run deadlock detection (and handle the resulting
791errors), or make sure only one process ever updates the database, ine one
792thread, e.g. by using only foreground requests (without a callback).
793
615=head2 FORK BEHAVIOUR 794=head1 FORK BEHAVIOUR
616 795
617This module should do "the right thing" when the process using it forks: 796This module should do "the right thing" when the process using it forks:
618 797
619Before the fork, IO::AIO enters a quiescent state where no requests 798Before the fork, BDB enters a quiescent state where no requests
620can be added in other threads and no results will be processed. After 799can be added in other threads and no results will be processed. After
621the fork the parent simply leaves the quiescent state and continues 800the fork the parent simply leaves the quiescent state and continues
622request/result processing, while the child frees the request/result queue 801request/result processing, while the child frees the request/result queue
623(so that the requests started before the fork will only be handled in the 802(so that the requests started before the fork will only be handled in the
624parent). Threads will be started on demand until the limit set in the 803parent). Threads will be started on demand until the limit set in the
625parent process has been reached again. 804parent process has been reached again.
626 805
627In short: the parent will, after a short pause, continue as if fork had 806In short: the parent will, after a short pause, continue as if fork had
628not been called, while the child will act as if IO::AIO has not been used 807not been called, while the child will act as if BDB has not been used
629yet. 808yet.
630 809
810Win32 note: there is no fork on win32, and perls emulation of it is too
811broken to be supported, so do not use BDB in a windows pseudo-fork, better
812yet, switch to a more capable platform.
813
631=head2 MEMORY USAGE 814=head1 MEMORY USAGE
632 815
633Per-request usage: 816Per-request usage:
634 817
635Each aio request uses - depending on your architecture - around 100-200 818Each aio request uses - depending on your architecture - around 100-200
636bytes of memory. In addition, stat requests need a stat buffer (possibly 819bytes of memory. In addition, stat requests need a stat buffer (possibly
… …
645 828
646In the execution phase, some aio requests require more memory for 829In the execution phase, some aio requests require more memory for
647temporary buffers, and each thread requires a stack and other data 830temporary buffers, and each thread requires a stack and other data
648structures (usually around 16k-128k, depending on the OS). 831structures (usually around 16k-128k, depending on the OS).
649 832
833=head1 WIN32 FILENAMES/DATABASE NAME MESS
834
835Perl on Win32 supports only ASCII filenames (the reason is that it abuses
836an internal flag to store wether a filename is Unicode or ANSI, but that
837flag is used for somethign else in the perl core, so there is no way to
838detect wether a filename is ANSI or Unicode-encoded). The BDB module
839tries to work around this issue by assuming that the filename is an ANSI
840filename and BDB was built for unicode support.
841
650=head1 KNOWN BUGS 842=head1 KNOWN BUGS
651 843
652Known bugs will be fixed in the next release, except: 844Known bugs will be fixed in the next release, except:
653 845
654 If you use a transaction in any request, and the request returns 846 If you use a transaction in any request, and the request returns
… …
656 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, 848 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
657 above. 849 above.
658 850
659=head1 SEE ALSO 851=head1 SEE ALSO
660 852
661L<Coro::AIO>. 853L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
854syntax), L<IO::AIO> (nice to have).
662 855
663=head1 AUTHOR 856=head1 AUTHOR
664 857
665 Marc Lehmann <schmorp@schmorp.de> 858 Marc Lehmann <schmorp@schmorp.de>
666 http://home.schmorp.de/ 859 http://home.schmorp.de/

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