1 | NAME |
1 | NAME |
2 | BDB - Asynchronous Berkeley DB access |
2 | BDB - Asynchronous Berkeley DB access |
3 | |
3 | |
4 | SYNOPSIS |
4 | SYNOPSIS |
5 | use BDB; |
5 | use BDB; |
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6 | |
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7 | my $env = db_env_create; |
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8 | |
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9 | mkdir "bdtest", 0700; |
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10 | db_env_open |
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11 | $env, |
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12 | "bdtest", |
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13 | BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL |
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14 | | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE, |
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15 | 0600; |
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16 | |
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17 | $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); |
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18 | |
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19 | my $db = db_create $env; |
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20 | db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE |
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21 | | BDB::READ_UNCOMMITTED, 0600; |
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22 | db_put $db, undef, "key", "data", 0, sub { |
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23 | db_del $db, undef, "key"; |
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24 | }; |
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25 | db_sync $db; |
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26 | |
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27 | # when you also use Coro, management is easy: |
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28 | use Coro::BDB; |
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29 | |
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30 | # automatic event loop intergration with AnyEvent: |
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31 | use AnyEvent::BDB; |
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32 | |
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33 | # automatic result processing with EV: |
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34 | my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb; |
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35 | |
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36 | # with Glib: |
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37 | add_watch Glib::IO BDB::poll_fileno, |
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38 | in => sub { BDB::poll_cb; 1 }; |
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39 | |
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40 | # or simply flush manually |
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41 | BDB::flush; |
6 | |
42 | |
7 | DESCRIPTION |
43 | DESCRIPTION |
8 | See the BerkeleyDB documentation |
44 | See the BerkeleyDB documentation |
9 | (<http://www.oracle.com/technology/documentation/berkeley-db/db/index.ht |
45 | (<http://www.oracle.com/technology/documentation/berkeley-db/db/index.ht |
10 | ml>). The BDB API is very similar to the C API (the translation has been |
46 | ml>). The BDB API is very similar to the C API (the translation has been |
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50 | Request has reached the end of its lifetime and holds no resources |
86 | Request has reached the end of its lifetime and holds no resources |
51 | anymore (except possibly for the Perl object, but its connection to |
87 | anymore (except possibly for the Perl object, but its connection to |
52 | the actual aio request is severed and calling its methods will |
88 | the actual aio request is severed and calling its methods will |
53 | either do nothing or result in a runtime error). |
89 | either do nothing or result in a runtime error). |
54 | |
90 | |
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91 | WIN32 FILENAMES/DATABASE NAME MESS |
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92 | Perl on Win32 supports only ASCII filenames (the reason is that it |
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93 | abuses an internal flag to store wether a filename is Unicode or ANSI, |
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94 | but that flag is used for somethign else in the perl core, so there is |
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95 | no way to detect wether a filename is ANSI or Unicode-encoded). The BDB |
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96 | module tries to work around this issue by assuming that the filename is |
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97 | an ANSI filename and BDB was built for unicode support. |
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98 | |
55 | BERKELEYDB FUNCTIONS |
99 | BERKELEYDB FUNCTIONS |
56 | All of these are functions. The create functions simply return a new |
100 | All of these are functions. The create functions simply return a new |
57 | object and never block. All the remaining functions all take an optional |
101 | object and never block. All the remaining functions take an optional |
58 | callback as last argument. If it is missing, then the fucntion will be |
102 | callback as last argument. If it is missing, then the function will be |
59 | executed synchronously. |
103 | executed synchronously. In both cases, $! will reflect the return value |
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104 | of the function. |
60 | |
105 | |
61 | BDB functions that cannot block (mostly functions that manipulate |
106 | BDB functions that cannot block (mostly functions that manipulate |
62 | settings) are method calls on the relevant objects, so the rule of thumb |
107 | settings) are method calls on the relevant objects, so the rule of thumb |
63 | is: if its a method, its not blocking, if its a function, it takes a |
108 | is: if it's a method, it's not blocking, if it's a function, it takes a |
64 | callback as last argument. |
109 | callback as last argument. |
65 | |
110 | |
66 | In the following, $int signifies an integer return value, "octetstring" |
111 | In the following, $int signifies an integer return value, "bdb_filename" |
67 | is a "binary string" (i.e. a perl string with no character indices |
112 | is a "filename" (octets on unix, madness on windows), "U32" is an |
68 | >255), "U32" is an unsigned 32 bit integer, "int" is some integer, "NV" |
113 | unsigned 32 bit integer, "int" is some integer, "NV" is a floating point |
69 | is a floating point value. |
114 | value. |
70 | |
115 | |
71 | The "SV *" types are generic perl scalars (for input and output of data |
116 | The "SV *" types are generic perl scalars (for input and output of data |
72 | values), and the "SV *callback" is the optional callback function to |
117 | values), and the "SV *callback" is the optional callback function to |
73 | call when the request is completed. |
118 | call when the request is completed. |
74 | |
119 | |
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81 | Functions in the BDB namespace, exported by default: |
126 | Functions in the BDB namespace, exported by default: |
82 | |
127 | |
83 | $env = db_env_create (U32 env_flags = 0) |
128 | $env = db_env_create (U32 env_flags = 0) |
84 | flags: RPCCLIENT |
129 | flags: RPCCLIENT |
85 | |
130 | |
86 | db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) |
131 | db_env_open (DB_ENV *env, bdb_filename db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) |
87 | open_flags: INIT_CDB INIT_LOCK INIT_LOG INIT_MPOOL INIT_REP INIT_TXN RECOVER RECOVER_FATAL USE_ENVIRON USE_ENVIRON_ROOT CREATE LOCKDOWN PRIVATE REGISTER SYSTEM_MEM |
132 | open_flags: INIT_CDB INIT_LOCK INIT_LOG INIT_MPOOL INIT_REP INIT_TXN RECOVER RECOVER_FATAL USE_ENVIRON USE_ENVIRON_ROOT CREATE LOCKDOWN PRIVATE REGISTER SYSTEM_MEM |
88 | db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) |
133 | db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) |
89 | db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
134 | db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
90 | flags: FORCE |
135 | flags: FORCE |
91 | db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) |
136 | db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) |
92 | atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST |
137 | atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST |
93 | db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) |
138 | db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) |
94 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
139 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
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140 | 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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141 | 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) |
95 | |
142 | |
96 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
143 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
97 | flags: XA_CREATE |
144 | flags: XA_CREATE |
98 | |
145 | |
99 | db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) |
146 | 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) |
100 | flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE |
147 | flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE |
101 | db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
148 | db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
102 | flags: DB_NOSYNC |
149 | flags: DB_NOSYNC |
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150 | db_upgrade (DB *db, bdb_filename file, U32 flags = 0, SV *callback = &PL_sv_undef) |
103 | db_compact (DB *db, DB_TXN_ornull *txn = 0, SV *start = 0, SV *stop = 0, SV *unused1 = 0, U32 flags = DB_FREE_SPACE, SV *unused2 = 0, SV *callback = &PL_sv_undef) |
151 | 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) |
104 | flags: FREELIST_ONLY FREE_SPACE |
152 | flags: FREELIST_ONLY FREE_SPACE |
105 | db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
153 | db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
106 | db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) |
154 | db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) |
107 | db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
155 | db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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178 | $int = $env->set_data_dir (const char *dir) |
226 | $int = $env->set_data_dir (const char *dir) |
179 | $int = $env->set_tmp_dir (const char *dir) |
227 | $int = $env->set_tmp_dir (const char *dir) |
180 | $int = $env->set_lg_dir (const char *dir) |
228 | $int = $env->set_lg_dir (const char *dir) |
181 | $int = $env->set_shm_key (long shm_key) |
229 | $int = $env->set_shm_key (long shm_key) |
182 | $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
230 | $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
183 | $int = $env->set_flags (U32 flags, int onoff) |
231 | $int = $env->set_flags (U32 flags, int onoff = 1) |
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232 | $int = $env->log_set_config (U32 flags, int onoff = 1) [v4.7] |
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233 | $int = $env->set_intermediate_dir_mode (const char *modestring) [v4.7] |
184 | $env->set_errfile (FILE *errfile = 0) |
234 | $env->set_errfile (FILE *errfile = 0) |
185 | $env->set_msgfile (FILE *msgfile = 0) |
235 | $env->set_msgfile (FILE *msgfile = 0) |
186 | $int = $env->set_verbose (U32 which, int onoff = 1) |
236 | $int = $env->set_verbose (U32 which, int onoff = 1) |
187 | $int = $env->set_encrypt (const char *password, U32 flags = 0) |
237 | $int = $env->set_encrypt (const char *password, U32 flags = 0) |
188 | $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
238 | $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
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193 | $int = $env->set_lk_max_lockers (U32 max) |
243 | $int = $env->set_lk_max_lockers (U32 max) |
194 | $int = $env->set_lk_max_locks (U32 max) |
244 | $int = $env->set_lk_max_locks (U32 max) |
195 | $int = $env->set_lk_max_objects (U32 max) |
245 | $int = $env->set_lk_max_objects (U32 max) |
196 | $int = $env->set_lg_bsize (U32 max) |
246 | $int = $env->set_lg_bsize (U32 max) |
197 | $int = $env->set_lg_max (U32 max) |
247 | $int = $env->set_lg_max (U32 max) |
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248 | $int = $env->mutex_set_increment (U32 increment) |
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249 | $int = $env->mutex_set_tas_spins (U32 tas_spins) |
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250 | $int = $env->mutex_set_max (U32 max) |
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251 | $int = $env->mutex_set_align (U32 align) |
198 | |
252 | |
199 | $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) |
253 | $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) |
200 | flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC |
254 | flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC |
201 | |
255 | |
202 | Example: |
256 | Example: |
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289 | DESTROY (DBC_ornull *dbc) |
343 | DESTROY (DBC_ornull *dbc) |
290 | CODE: |
344 | CODE: |
291 | if (dbc) |
345 | if (dbc) |
292 | dbc->c_close (dbc); |
346 | dbc->c_close (dbc); |
293 | |
347 | |
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348 | $int = $cursor->set_priority ($priority = PRIORITY_*) |
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349 | |
294 | Example: |
350 | Example: |
295 | my $c = $db->cursor; |
351 | my $c = $db->cursor; |
296 | |
352 | |
297 | for (;;) { |
353 | for (;;) { |
298 | db_c_get $c, my $key, my $data, BDB::NEXT; |
354 | db_c_get $c, my $key, my $data, BDB::NEXT; |
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316 | flags: SEQ_DEC SEQ_INC SEQ_WRAP |
372 | flags: SEQ_DEC SEQ_INC SEQ_WRAP |
317 | $int = $seq->set_range (db_seq_t min, db_seq_t max) |
373 | $int = $seq->set_range (db_seq_t min, db_seq_t max) |
318 | |
374 | |
319 | Example: |
375 | Example: |
320 | my $seq = $db->sequence; |
376 | my $seq = $db->sequence; |
321 | |
377 | |
322 | db_sequence_open $seq, undef, "seq", BDB::CREATE; |
378 | db_sequence_open $seq, undef, "seq", BDB::CREATE; |
323 | db_sequence_get $seq, undef, 1, my $value; |
379 | db_sequence_get $seq, undef, 1, my $value; |
324 | |
380 | |
325 | SUPPORT FUNCTIONS |
381 | SUPPORT FUNCTIONS |
326 | EVENT PROCESSING AND EVENT LOOP INTEGRATION |
382 | EVENT PROCESSING AND EVENT LOOP INTEGRATION |
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383 | $msg = BDB::strerror [$errno] |
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384 | Returns the string corresponding to the given errno value. If no |
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385 | argument is given, use $!. |
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386 | |
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387 | Note that the BDB module also patches the $! variable directly, so |
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388 | you should be able to get a bdb error string by simply stringifying |
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389 | $!. |
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390 | |
327 | $fileno = BDB::poll_fileno |
391 | $fileno = BDB::poll_fileno |
328 | Return the *request result pipe file descriptor*. This filehandle |
392 | Return the *request result pipe file descriptor*. This filehandle |
329 | must be polled for reading by some mechanism outside this module |
393 | must be polled for reading by some mechanism outside this module |
330 | (e.g. Event or select, see below or the SYNOPSIS). If the pipe |
394 | (e.g. Event or select, see below or the SYNOPSIS). If the pipe |
331 | becomes readable you have to call "poll_cb" to check the results. |
395 | becomes readable you have to call "poll_cb" to check the results. |
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367 | interactiveness when perl is not fast enough to process all requests |
431 | interactiveness when perl is not fast enough to process all requests |
368 | in time. |
432 | in time. |
369 | |
433 | |
370 | For interactive programs, values such as 0.01 to 0.1 should be fine. |
434 | For interactive programs, values such as 0.01 to 0.1 should be fine. |
371 | |
435 | |
372 | Example: Install an Event watcher that automatically calls |
436 | Example: Install an EV watcher that automatically calls BDB::poll_cb |
373 | BDB::poll_cb with low priority, to ensure that other parts of the |
437 | with low priority, to ensure that other parts of the program get the |
374 | program get the CPU sometimes even under high AIO load. |
438 | CPU sometimes even under high load. |
375 | |
439 | |
376 | # try not to spend much more than 0.1s in poll_cb |
440 | # try not to spend much more than 0.1s in poll_cb |
377 | BDB::max_poll_time 0.1; |
441 | BDB::max_poll_time 0.1; |
378 | |
442 | |
379 | # use a low priority so other tasks have priority |
443 | my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb); |
380 | Event->io (fd => BDB::poll_fileno, |
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381 | poll => 'r', nice => 1, |
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382 | cb => &BDB::poll_cb); |
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383 | |
444 | |
384 | BDB::poll_wait |
445 | BDB::poll_wait |
385 | If there are any outstanding requests and none of them in the result |
446 | If there are any outstanding requests and none of them in the result |
386 | phase, wait till the result filehandle becomes ready for reading |
447 | phase, wait till the result filehandle becomes ready for reading |
387 | (simply does a "select" on the filehandle. This is useful if you |
448 | (simply does a "select" on the filehandle. This is useful if you |
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396 | equivalent to: |
457 | equivalent to: |
397 | |
458 | |
398 | BDB::poll_wait, BDB::poll_cb |
459 | BDB::poll_wait, BDB::poll_cb |
399 | |
460 | |
400 | BDB::flush |
461 | BDB::flush |
401 | Wait till all outstanding AIO requests have been handled. |
462 | Wait till all outstanding BDB requests have been handled. |
402 | |
463 | |
403 | Strictly equivalent to: |
464 | Strictly equivalent to: |
404 | |
465 | |
405 | BDB::poll_wait, BDB::poll_cb |
466 | BDB::poll_wait, BDB::poll_cb |
406 | while BDB::nreqs; |
467 | while BDB::nreqs; |
407 | |
468 | |
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469 | VERSION CHECKING |
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470 | BerkeleyDB comes in various versions, many of them have minor |
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471 | incompatibilities. This means that traditional "at least version x.x" |
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472 | checks are often not sufficient. |
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473 | |
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474 | Example: set the log_autoremove option in a way compatible with <v.47 |
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475 | and v4.7. Note the use of & on the constants to avoid triggering a |
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476 | compiletime bug when the symbol isn't available. |
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477 | |
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478 | $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7; |
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479 | $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7; |
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480 | |
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481 | BDB::VERSION |
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482 | The "BDB::VERSION" function, when called without arguments, returns |
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483 | the Berkeley DB version as a v-string (usually with 3 components). |
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484 | You should use "lt" and "ge" operators exclusively to make |
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485 | comparisons. |
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486 | |
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487 | Example: check for at least version 4.7. |
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488 | |
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489 | BDB::VERSION ge v4.7 or die; |
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490 | |
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491 | BDB::VERSION min-version |
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492 | Returns true if the BDB version is at least the given version |
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493 | (specified as a v-string), false otherwise. |
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494 | |
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495 | Example: check for at least version 4.5. |
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496 | |
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497 | BDB::VERSION v4.7 or die; |
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498 | |
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499 | BDB::VERSION min-version, max-version |
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500 | Returns true of the BDB version is at least version "min-version" |
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501 | (specify "undef" or "v0" for any minimum version) and less then |
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502 | "max-version". |
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503 | |
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504 | Example: check wether version is strictly less then v4.7. |
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505 | |
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506 | BDB::VERSION v0, v4.7 |
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507 | or die "version 4.7 is not yet supported"; |
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508 | |
408 | CONTROLLING THE NUMBER OF THREADS |
509 | CONTROLLING THE NUMBER OF THREADS |
409 | BDB::min_parallel $nthreads |
510 | BDB::min_parallel $nthreads |
410 | Set the minimum number of AIO threads to $nthreads. The current |
511 | Set the minimum number of BDB threads to $nthreads. The current |
411 | default is 8, which means eight asynchronous operations can execute |
512 | default is 8, which means eight asynchronous operations can execute |
412 | concurrently at any one time (the number of outstanding requests, |
513 | concurrently at any one time (the number of outstanding requests, |
413 | however, is unlimited). |
514 | however, is unlimited). |
414 | |
515 | |
415 | BDB starts threads only on demand, when an AIO request is queued and |
516 | BDB starts threads only on demand, when an BDB request is queued and |
416 | no free thread exists. Please note that queueing up a hundred |
517 | no free thread exists. Please note that queueing up a hundred |
417 | requests can create demand for a hundred threads, even if it turns |
518 | requests can create demand for a hundred threads, even if it turns |
418 | out that everything is in the cache and could have been processed |
519 | out that everything is in the cache and could have been processed |
419 | faster by a single thread. |
520 | faster by a single thread. |
420 | |
521 | |
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426 | Under most circumstances you don't need to call this function, as |
527 | Under most circumstances you don't need to call this function, as |
427 | the module selects a default that is suitable for low to moderate |
528 | the module selects a default that is suitable for low to moderate |
428 | load. |
529 | load. |
429 | |
530 | |
430 | BDB::max_parallel $nthreads |
531 | BDB::max_parallel $nthreads |
431 | Sets the maximum number of AIO threads to $nthreads. If more than |
532 | Sets the maximum number of BDB threads to $nthreads. If more than |
432 | the specified number of threads are currently running, this function |
533 | the specified number of threads are currently running, this function |
433 | kills them. This function blocks until the limit is reached. |
534 | kills them. This function blocks until the limit is reached. |
434 | |
535 | |
435 | While $nthreads are zero, aio requests get queued but not executed |
536 | While $nthreads are zero, aio requests get queued but not executed |
436 | until the number of threads has been increased again. |
537 | until the number of threads has been increased again. |
… | |
… | |
475 | (with large values). |
576 | (with large values). |
476 | |
577 | |
477 | BDB::set_sync_prepare $cb |
578 | BDB::set_sync_prepare $cb |
478 | Sets a callback that is called whenever a request is created without |
579 | Sets a callback that is called whenever a request is created without |
479 | an explicit callback. It has to return two code references. The |
580 | an explicit callback. It has to return two code references. The |
480 | first is used as the request callback, and the second is called to |
581 | first is used as the request callback (it should save the return |
481 | wait until the first callback has been called. The default |
582 | status), and the second is called to wait until the first callback |
|
|
583 | has been called (it must set $! to the return status). |
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|
584 | |
|
|
585 | This mechanism can be used to include BDB into other event |
|
|
586 | mechanisms, such as AnyEvent::BDB or Coro::BDB. |
|
|
587 | |
482 | implementation works like this: |
588 | The default implementation works like this: |
483 | |
589 | |
484 | sub { |
590 | sub { |
485 | my $status; |
591 | my $status; |
486 | ( |
592 | ( |
487 | sub { $status = $! }, |
593 | sub { $status = $! }, |
488 | sub { BDB::poll while !defined $status; $! = $status }, |
594 | sub { BDB::poll while !defined $status; $! = $status }, |
489 | ) |
595 | ) |
490 | } |
596 | } |
491 | |
597 | |
|
|
598 | It simply blocks the process till the request has finished and then |
|
|
599 | sets $! to the return value. This means that if you don't use a |
|
|
600 | callback, BDB will simply fall back to synchronous operations. |
|
|
601 | |
492 | STATISTICAL INFORMATION |
602 | STATISTICAL INFORMATION |
493 | BDB::nreqs |
603 | BDB::nreqs |
494 | Returns the number of requests currently in the ready, execute or |
604 | Returns the number of requests currently in the ready, execute or |
495 | pending states (i.e. for which their callback has not been invoked |
605 | pending states (i.e. for which their callback has not been invoked |
496 | yet). |
606 | yet). |
… | |
… | |
509 | (executed, but not yet processed by poll_cb). |
619 | (executed, but not yet processed by poll_cb). |
510 | |
620 | |
511 | FORK BEHAVIOUR |
621 | FORK BEHAVIOUR |
512 | This module should do "the right thing" when the process using it forks: |
622 | This module should do "the right thing" when the process using it forks: |
513 | |
623 | |
514 | Before the fork, IO::AIO enters a quiescent state where no requests can |
624 | Before the fork, BDB enters a quiescent state where no requests can be |
515 | be added in other threads and no results will be processed. After the |
625 | added in other threads and no results will be processed. After the fork |
516 | fork the parent simply leaves the quiescent state and continues |
626 | the parent simply leaves the quiescent state and continues |
517 | request/result processing, while the child frees the request/result |
627 | request/result processing, while the child frees the request/result |
518 | queue (so that the requests started before the fork will only be handled |
628 | queue (so that the requests started before the fork will only be handled |
519 | in the parent). Threads will be started on demand until the limit set in |
629 | in the parent). Threads will be started on demand until the limit set in |
520 | the parent process has been reached again. |
630 | the parent process has been reached again. |
521 | |
631 | |
522 | In short: the parent will, after a short pause, continue as if fork had |
632 | In short: the parent will, after a short pause, continue as if fork had |
523 | not been called, while the child will act as if IO::AIO has not been |
633 | not been called, while the child will act as if BDB has not been used |
524 | used yet. |
634 | yet. |
|
|
635 | |
|
|
636 | Win32 note: there is no fork on win32, and perls emulation of it is too |
|
|
637 | broken to be supported, so do not use BDB in a windows pseudo-fork, |
|
|
638 | better yet, switch to a more capable platform. |
525 | |
639 | |
526 | MEMORY USAGE |
640 | MEMORY USAGE |
527 | Per-request usage: |
641 | Per-request usage: |
528 | |
642 | |
529 | Each aio request uses - depending on your architecture - around 100-200 |
643 | Each aio request uses - depending on your architecture - around 100-200 |
… | |
… | |
548 | with an operating system error or DB_LOCK_NOTGRANTED, the internal |
662 | with an operating system error or DB_LOCK_NOTGRANTED, the internal |
549 | TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, |
663 | TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, |
550 | above. |
664 | above. |
551 | |
665 | |
552 | SEE ALSO |
666 | SEE ALSO |
553 | Coro::AIO. |
667 | AnyEvent::BDB (event loop integration), Coro::BDB (more natural syntax), |
|
|
668 | IO::AIO (nice to have). |
554 | |
669 | |
555 | AUTHOR |
670 | AUTHOR |
556 | Marc Lehmann <schmorp@schmorp.de> |
671 | Marc Lehmann <schmorp@schmorp.de> |
557 | http://home.schmorp.de/ |
672 | http://home.schmorp.de/ |
558 | |
673 | |