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3 | BDB - Asynchronous Berkeley DB access |
3 | BDB - Asynchronous Berkeley DB access |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use BDB; |
7 | use BDB; |
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8 | |
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9 | my $env = db_env_create; |
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10 | |
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11 | mkdir "bdtest", 0700; |
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12 | db_env_open |
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13 | $env, |
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14 | "bdtest", |
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15 | BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL |
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16 | | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE, |
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17 | 0600; |
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18 | |
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19 | $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); |
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20 | |
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21 | my $db = db_create $env; |
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22 | db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE |
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23 | | BDB::READ_UNCOMMITTED, 0600; |
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24 | db_put $db, undef, "key", "data", 0, sub { |
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25 | db_del $db, undef, "key"; |
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26 | }; |
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27 | db_sync $db; |
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28 | |
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29 | # when you also use Coro, management is easy: |
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30 | use Coro::BDB; |
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31 | |
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32 | # automatic event loop intergration with AnyEvent: |
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33 | use AnyEvent::BDB; |
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34 | |
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35 | # automatic result processing with EV: |
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36 | my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb; |
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37 | |
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38 | # with Glib: |
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39 | add_watch Glib::IO BDB::poll_fileno, |
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40 | in => sub { BDB::poll_cb; 1 }; |
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41 | |
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42 | # or simply flush manually |
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43 | BDB::flush; |
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44 | |
8 | |
45 | |
9 | =head1 DESCRIPTION |
46 | =head1 DESCRIPTION |
10 | |
47 | |
11 | See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). |
48 | See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). |
12 | The BDB API is very similar to the C API (the translation has been very faithful). |
49 | The BDB API is very similar to the C API (the translation has been very faithful). |
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72 | use strict 'vars'; |
109 | use strict 'vars'; |
73 | |
110 | |
74 | use base 'Exporter'; |
111 | use base 'Exporter'; |
75 | |
112 | |
76 | BEGIN { |
113 | BEGIN { |
77 | our $VERSION = '1.2'; |
114 | our $VERSION = '1.6'; |
78 | |
115 | |
79 | our @BDB_REQ = qw( |
116 | our @BDB_REQ = qw( |
80 | db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect |
117 | db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect |
81 | db_env_memp_sync db_env_memp_trickle |
118 | 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 |
119 | db_open db_close db_compact db_sync db_upgrade |
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120 | db_put db_get db_pget db_del db_key_range |
83 | db_txn_commit db_txn_abort db_txn_finish |
121 | 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 |
122 | 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 |
123 | db_sequence_open db_sequence_close |
86 | db_sequence_get db_sequence_remove |
124 | db_sequence_get db_sequence_remove |
87 | ); |
125 | ); |
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95 | |
133 | |
96 | require XSLoader; |
134 | require XSLoader; |
97 | XSLoader::load ("BDB", $VERSION); |
135 | XSLoader::load ("BDB", $VERSION); |
98 | } |
136 | } |
99 | |
137 | |
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138 | =head2 WIN32 FILENAMES/DATABASE NAME MESS |
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139 | |
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140 | Perl on Win32 supports only ASCII filenames (the reason is that it abuses |
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141 | an internal flag to store wether a filename is Unicode or ANSI, but that |
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142 | flag is used for somethign else in the perl core, so there is no way to |
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143 | detect wether a filename is ANSI or Unicode-encoded). The BDB module |
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144 | tries to work around this issue by assuming that the filename is an ANSI |
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145 | filename and BDB was built for unicode support. |
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146 | |
100 | =head2 BERKELEYDB FUNCTIONS |
147 | =head2 BERKELEYDB FUNCTIONS |
101 | |
148 | |
102 | All of these are functions. The create functions simply return a new |
149 | All of these are functions. The create functions simply return a new |
103 | object and never block. All the remaining functions all take an optional |
150 | object and never block. All the remaining functions take an optional |
104 | callback as last argument. If it is missing, then the fucntion will be |
151 | callback as last argument. If it is missing, then the function will be |
105 | executed synchronously. |
152 | executed synchronously. In both cases, C<$!> will reflect the return value |
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153 | of the function. |
106 | |
154 | |
107 | BDB functions that cannot block (mostly functions that manipulate |
155 | BDB functions that cannot block (mostly functions that manipulate |
108 | settings) are method calls on the relevant objects, so the rule of thumb |
156 | settings) are method calls on the relevant objects, so the rule of thumb |
109 | is: if its a method, its not blocking, if its a function, it takes a |
157 | is: if it's a method, it's not blocking, if it's a function, it takes a |
110 | callback as last argument. |
158 | callback as last argument. |
111 | |
159 | |
112 | In the following, C<$int> signifies an integer return value, |
160 | In the following, C<$int> signifies an integer return value, |
113 | C<octetstring> is a "binary string" (i.e. a perl string with no character |
161 | C<bdb_filename> is a "filename" (octets on unix, madness on windows), |
114 | indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some |
162 | C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a |
115 | integer, C<NV> is a floating point value. |
163 | floating point value. |
116 | |
164 | |
117 | The C<SV *> types are generic perl scalars (for input and output of data |
165 | The C<SV *> types are generic perl scalars (for input and output of data |
118 | values), and the C<SV *callback> is the optional callback function to call |
166 | values), and the C<SV *callback> is the optional callback function to call |
119 | when the request is completed. |
167 | when the request is completed. |
120 | |
168 | |
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128 | Functions in the BDB namespace, exported by default: |
176 | Functions in the BDB namespace, exported by default: |
129 | |
177 | |
130 | $env = db_env_create (U32 env_flags = 0) |
178 | $env = db_env_create (U32 env_flags = 0) |
131 | flags: RPCCLIENT |
179 | flags: RPCCLIENT |
132 | |
180 | |
133 | db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) |
181 | db_env_open (DB_ENV *env, bdb_filename db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) |
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 |
182 | 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) |
183 | db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) |
136 | db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
184 | db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
137 | flags: FORCE |
185 | 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) |
186 | db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) |
139 | atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST |
187 | 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) |
188 | db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) |
141 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
189 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
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190 | db_env_dbremove (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef) |
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191 | db_env_dbrename (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = &PL_sv_undef) |
142 | |
192 | |
143 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
193 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
144 | flags: XA_CREATE |
194 | flags: XA_CREATE |
145 | |
195 | |
146 | db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) |
196 | db_open (DB *db, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) |
147 | flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE |
197 | 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) |
198 | db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
149 | flags: DB_NOSYNC |
199 | flags: DB_NOSYNC |
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200 | db_upgrade (DB *db, bdb_filename file, U32 flags = 0, SV *callback = &PL_sv_undef) |
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) |
201 | 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) |
151 | flags: FREELIST_ONLY FREE_SPACE |
202 | flags: FREELIST_ONLY FREE_SPACE |
152 | db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
203 | db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
153 | db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) |
204 | db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) |
154 | db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
205 | db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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227 | $int = $env->set_data_dir (const char *dir) |
278 | $int = $env->set_data_dir (const char *dir) |
228 | $int = $env->set_tmp_dir (const char *dir) |
279 | $int = $env->set_tmp_dir (const char *dir) |
229 | $int = $env->set_lg_dir (const char *dir) |
280 | $int = $env->set_lg_dir (const char *dir) |
230 | $int = $env->set_shm_key (long shm_key) |
281 | $int = $env->set_shm_key (long shm_key) |
231 | $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
282 | $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
232 | $int = $env->set_flags (U32 flags, int onoff) |
283 | $int = $env->set_flags (U32 flags, int onoff = 1) |
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284 | $int = $env->log_set_config (U32 flags, int onoff = 1) [v4.7] |
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285 | $int = $env->set_intermediate_dir_mode (const char *modestring) [v4.7] |
233 | $env->set_errfile (FILE *errfile = 0) |
286 | $env->set_errfile (FILE *errfile = 0) |
234 | $env->set_msgfile (FILE *msgfile = 0) |
287 | $env->set_msgfile (FILE *msgfile = 0) |
235 | $int = $env->set_verbose (U32 which, int onoff = 1) |
288 | $int = $env->set_verbose (U32 which, int onoff = 1) |
236 | $int = $env->set_encrypt (const char *password, U32 flags = 0) |
289 | $int = $env->set_encrypt (const char *password, U32 flags = 0) |
237 | $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
290 | $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
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242 | $int = $env->set_lk_max_lockers (U32 max) |
295 | $int = $env->set_lk_max_lockers (U32 max) |
243 | $int = $env->set_lk_max_locks (U32 max) |
296 | $int = $env->set_lk_max_locks (U32 max) |
244 | $int = $env->set_lk_max_objects (U32 max) |
297 | $int = $env->set_lk_max_objects (U32 max) |
245 | $int = $env->set_lg_bsize (U32 max) |
298 | $int = $env->set_lg_bsize (U32 max) |
246 | $int = $env->set_lg_max (U32 max) |
299 | $int = $env->set_lg_max (U32 max) |
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300 | $int = $env->mutex_set_increment (U32 increment) |
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301 | $int = $env->mutex_set_tas_spins (U32 tas_spins) |
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302 | $int = $env->mutex_set_max (U32 max) |
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303 | $int = $env->mutex_set_align (U32 align) |
247 | |
304 | |
248 | $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) |
305 | $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) |
249 | flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC |
306 | flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC |
250 | |
307 | |
251 | =head4 Example: |
308 | =head4 Example: |
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346 | DESTROY (DBC_ornull *dbc) |
403 | DESTROY (DBC_ornull *dbc) |
347 | CODE: |
404 | CODE: |
348 | if (dbc) |
405 | if (dbc) |
349 | dbc->c_close (dbc); |
406 | dbc->c_close (dbc); |
350 | |
407 | |
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408 | $int = $cursor->set_priority ($priority = PRIORITY_*) |
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409 | |
351 | =head4 Example: |
410 | =head4 Example: |
352 | |
411 | |
353 | my $c = $db->cursor; |
412 | my $c = $db->cursor; |
354 | |
413 | |
355 | for (;;) { |
414 | for (;;) { |
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388 | |
447 | |
389 | =head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION |
448 | =head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION |
390 | |
449 | |
391 | =over 4 |
450 | =over 4 |
392 | |
451 | |
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452 | =item $msg = BDB::strerror [$errno] |
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453 | |
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454 | Returns the string corresponding to the given errno value. If no argument |
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455 | is given, use C<$!>. |
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456 | |
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457 | Note that the BDB module also patches the C<$!> variable directly, so you |
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458 | should be able to get a bdb error string by simply stringifying C<$!>. |
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459 | |
393 | =item $fileno = BDB::poll_fileno |
460 | =item $fileno = BDB::poll_fileno |
394 | |
461 | |
395 | Return the I<request result pipe file descriptor>. This filehandle must be |
462 | Return the I<request result pipe file descriptor>. This filehandle must be |
396 | polled for reading by some mechanism outside this module (e.g. Event or |
463 | polled for reading by some mechanism outside this module (e.g. Event or |
397 | select, see below or the SYNOPSIS). If the pipe becomes readable you have |
464 | select, see below or the SYNOPSIS). If the pipe becomes readable you have |
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435 | interactiveness when perl is not fast enough to process all requests in |
502 | interactiveness when perl is not fast enough to process all requests in |
436 | time. |
503 | time. |
437 | |
504 | |
438 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
505 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
439 | |
506 | |
440 | Example: Install an Event watcher that automatically calls |
507 | Example: Install an EV watcher that automatically calls |
441 | BDB::poll_cb with low priority, to ensure that other parts of the |
508 | BDB::poll_cb with low priority, to ensure that other parts of the |
442 | program get the CPU sometimes even under high AIO load. |
509 | program get the CPU sometimes even under high load. |
443 | |
510 | |
444 | # try not to spend much more than 0.1s in poll_cb |
511 | # try not to spend much more than 0.1s in poll_cb |
445 | BDB::max_poll_time 0.1; |
512 | BDB::max_poll_time 0.1; |
446 | |
513 | |
447 | # use a low priority so other tasks have priority |
514 | my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb); |
448 | Event->io (fd => BDB::poll_fileno, |
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449 | poll => 'r', nice => 1, |
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450 | cb => &BDB::poll_cb); |
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451 | |
515 | |
452 | =item BDB::poll_wait |
516 | =item BDB::poll_wait |
453 | |
517 | |
454 | If there are any outstanding requests and none of them in the result |
518 | If there are any outstanding requests and none of them in the result |
455 | phase, wait till the result filehandle becomes ready for reading (simply |
519 | phase, wait till the result filehandle becomes ready for reading (simply |
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467 | |
531 | |
468 | BDB::poll_wait, BDB::poll_cb |
532 | BDB::poll_wait, BDB::poll_cb |
469 | |
533 | |
470 | =item BDB::flush |
534 | =item BDB::flush |
471 | |
535 | |
472 | Wait till all outstanding AIO requests have been handled. |
536 | Wait till all outstanding BDB requests have been handled. |
473 | |
537 | |
474 | Strictly equivalent to: |
538 | Strictly equivalent to: |
475 | |
539 | |
476 | BDB::poll_wait, BDB::poll_cb |
540 | BDB::poll_wait, BDB::poll_cb |
477 | while BDB::nreqs; |
541 | while BDB::nreqs; |
478 | |
542 | |
479 | =back |
543 | =back |
480 | |
544 | |
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545 | =head3 VERSION CHECKING |
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546 | |
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547 | BerkeleyDB comes in various versions, many of them have minor |
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548 | incompatibilities. This means that traditional "at least version x.x" |
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549 | checks are often not sufficient. |
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550 | |
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551 | Example: set the log_autoremove option in a way compatible with <v.47 and |
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552 | v4.7. Note the use of & on the constants to avoid triggering a compiletime |
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553 | bug when the symbol isn't available. |
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554 | |
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555 | $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7; |
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556 | $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7; |
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557 | |
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558 | =over 4 |
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559 | |
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560 | =item BDB::VERSION |
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561 | |
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562 | The C<BDB::VERSION> function, when called without arguments, returns the |
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563 | Berkeley DB version as a v-string (usually with 3 components). You should |
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564 | use C<lt> and C<ge> operators exclusively to make comparisons. |
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565 | |
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566 | Example: check for at least version 4.7. |
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567 | |
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568 | BDB::VERSION ge v4.7 or die; |
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569 | |
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570 | =item BDB::VERSION min-version |
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571 | |
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572 | Returns true if the BDB version is at least the given version (specified |
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573 | as a v-string), false otherwise. |
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574 | |
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575 | Example: check for at least version 4.5. |
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576 | |
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577 | BDB::VERSION v4.7 or die; |
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578 | |
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579 | =item BDB::VERSION min-version, max-version |
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580 | |
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581 | Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version) |
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582 | and less then C<max-version>. |
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583 | |
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584 | Example: check wether version is strictly less then v4.7. |
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585 | |
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586 | BDB::VERSION v0, v4.7 |
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587 | or die "version 4.7 is not yet supported"; |
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588 | |
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589 | =back |
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590 | |
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591 | =cut |
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592 | |
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593 | sub VERSION { |
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594 | if (@_ > 0) { |
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595 | return undef if VERSION_v lt $_[0]; |
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596 | if (@_ > 1) { |
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597 | return undef if VERSION_v ge $_[1]; |
|
|
598 | } |
|
|
599 | } |
|
|
600 | |
|
|
601 | VERSION_v |
|
|
602 | } |
|
|
603 | |
481 | =head3 CONTROLLING THE NUMBER OF THREADS |
604 | =head3 CONTROLLING THE NUMBER OF THREADS |
482 | |
605 | |
483 | =over 4 |
606 | =over 4 |
484 | |
607 | |
485 | =item BDB::min_parallel $nthreads |
608 | =item BDB::min_parallel $nthreads |
486 | |
609 | |
487 | Set the minimum number of AIO threads to C<$nthreads>. The current |
610 | Set the minimum number of BDB threads to C<$nthreads>. The current |
488 | default is C<8>, which means eight asynchronous operations can execute |
611 | default is C<8>, which means eight asynchronous operations can execute |
489 | concurrently at any one time (the number of outstanding requests, |
612 | concurrently at any one time (the number of outstanding requests, |
490 | however, is unlimited). |
613 | however, is unlimited). |
491 | |
614 | |
492 | BDB starts threads only on demand, when an AIO request is queued and |
615 | BDB starts threads only on demand, when an BDB request is queued and |
493 | no free thread exists. Please note that queueing up a hundred requests can |
616 | no free thread exists. Please note that queueing up a hundred requests can |
494 | create demand for a hundred threads, even if it turns out that everything |
617 | create demand for a hundred threads, even if it turns out that everything |
495 | is in the cache and could have been processed faster by a single thread. |
618 | is in the cache and could have been processed faster by a single thread. |
496 | |
619 | |
497 | It is recommended to keep the number of threads relatively low, as some |
620 | It is recommended to keep the number of threads relatively low, as some |
… | |
… | |
502 | Under most circumstances you don't need to call this function, as the |
625 | Under most circumstances you don't need to call this function, as the |
503 | module selects a default that is suitable for low to moderate load. |
626 | module selects a default that is suitable for low to moderate load. |
504 | |
627 | |
505 | =item BDB::max_parallel $nthreads |
628 | =item BDB::max_parallel $nthreads |
506 | |
629 | |
507 | Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
630 | Sets the maximum number of BDB threads to C<$nthreads>. If more than the |
508 | specified number of threads are currently running, this function kills |
631 | specified number of threads are currently running, this function kills |
509 | them. This function blocks until the limit is reached. |
632 | them. This function blocks until the limit is reached. |
510 | |
633 | |
511 | While C<$nthreads> are zero, aio requests get queued but not executed |
634 | While C<$nthreads> are zero, aio requests get queued but not executed |
512 | until the number of threads has been increased again. |
635 | until the number of threads has been increased again. |
… | |
… | |
551 | |
674 | |
552 | =item BDB::set_sync_prepare $cb |
675 | =item BDB::set_sync_prepare $cb |
553 | |
676 | |
554 | Sets a callback that is called whenever a request is created without an |
677 | Sets a callback that is called whenever a request is created without an |
555 | explicit callback. It has to return two code references. The first is used |
678 | explicit callback. It has to return two code references. The first is used |
556 | as the request callback, and the second is called to wait until the first |
679 | as the request callback (it should save the return status), and the second |
|
|
680 | is called to wait until the first callback has been called (it must set |
|
|
681 | C<$!> to the return status). |
|
|
682 | |
|
|
683 | This mechanism can be used to include BDB into other event mechanisms, |
|
|
684 | such as L<AnyEvent::BDB> or L<Coro::BDB>. |
|
|
685 | |
557 | callback has been called. The default implementation works like this: |
686 | The default implementation works like this: |
558 | |
687 | |
559 | sub { |
688 | sub { |
560 | my $status; |
689 | my $status; |
561 | ( |
690 | ( |
562 | sub { $status = $! }, |
691 | sub { $status = $! }, |
563 | sub { BDB::poll while !defined $status; $! = $status }, |
692 | sub { BDB::poll while !defined $status; $! = $status }, |
564 | ) |
693 | ) |
565 | } |
694 | } |
|
|
695 | |
|
|
696 | It simply blocks the process till the request has finished and then sets |
|
|
697 | C<$!> to the return value. This means that if you don't use a callback, |
|
|
698 | BDB will simply fall back to synchronous operations. |
566 | |
699 | |
567 | =back |
700 | =back |
568 | |
701 | |
569 | =head3 STATISTICAL INFORMATION |
702 | =head3 STATISTICAL INFORMATION |
570 | |
703 | |
… | |
… | |
615 | |
748 | |
616 | =head2 FORK BEHAVIOUR |
749 | =head2 FORK BEHAVIOUR |
617 | |
750 | |
618 | This module should do "the right thing" when the process using it forks: |
751 | This module should do "the right thing" when the process using it forks: |
619 | |
752 | |
620 | Before the fork, IO::AIO enters a quiescent state where no requests |
753 | Before the fork, BDB enters a quiescent state where no requests |
621 | can be added in other threads and no results will be processed. After |
754 | can be added in other threads and no results will be processed. After |
622 | the fork the parent simply leaves the quiescent state and continues |
755 | the fork the parent simply leaves the quiescent state and continues |
623 | request/result processing, while the child frees the request/result queue |
756 | request/result processing, while the child frees the request/result queue |
624 | (so that the requests started before the fork will only be handled in the |
757 | (so that the requests started before the fork will only be handled in the |
625 | parent). Threads will be started on demand until the limit set in the |
758 | parent). Threads will be started on demand until the limit set in the |
626 | parent process has been reached again. |
759 | parent process has been reached again. |
627 | |
760 | |
628 | In short: the parent will, after a short pause, continue as if fork had |
761 | In short: the parent will, after a short pause, continue as if fork had |
629 | not been called, while the child will act as if IO::AIO has not been used |
762 | not been called, while the child will act as if BDB has not been used |
630 | yet. |
763 | yet. |
|
|
764 | |
|
|
765 | Win32 note: there is no fork on win32, and perls emulation of it is too |
|
|
766 | broken to be supported, so do not use BDB in a windows pseudo-fork, better |
|
|
767 | yet, switch to a more capable platform. |
631 | |
768 | |
632 | =head2 MEMORY USAGE |
769 | =head2 MEMORY USAGE |
633 | |
770 | |
634 | Per-request usage: |
771 | Per-request usage: |
635 | |
772 | |
… | |
… | |
657 | TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, |
794 | TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, |
658 | above. |
795 | above. |
659 | |
796 | |
660 | =head1 SEE ALSO |
797 | =head1 SEE ALSO |
661 | |
798 | |
662 | L<Coro::AIO>. |
799 | L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural |
|
|
800 | syntax), L<IO::AIO> (nice to have). |
663 | |
801 | |
664 | =head1 AUTHOR |
802 | =head1 AUTHOR |
665 | |
803 | |
666 | Marc Lehmann <schmorp@schmorp.de> |
804 | Marc Lehmann <schmorp@schmorp.de> |
667 | http://home.schmorp.de/ |
805 | http://home.schmorp.de/ |