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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 result processing with AnyEvent: |
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33 | our $FH; open $FH, "<&=" . BDB::poll_fileno; |
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34 | our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb); |
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35 | |
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36 | # automatic result processing with EV: |
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37 | my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb; |
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38 | |
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39 | # with Glib: |
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40 | add_watch Glib::IO BDB::poll_fileno, |
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41 | in => sub { BDB::poll_cb; 1 }; |
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42 | |
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43 | # or simply flush manually |
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44 | BDB::flush; |
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45 | |
8 | |
46 | |
9 | =head1 DESCRIPTION |
47 | =head1 DESCRIPTION |
10 | |
48 | |
11 | See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). |
49 | 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). |
50 | The BDB API is very similar to the C API (the translation has been very faithful). |
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72 | use strict 'vars'; |
110 | use strict 'vars'; |
73 | |
111 | |
74 | use base 'Exporter'; |
112 | use base 'Exporter'; |
75 | |
113 | |
76 | BEGIN { |
114 | BEGIN { |
77 | our $VERSION = '1.1'; |
115 | our $VERSION = '1.44'; |
78 | |
116 | |
79 | our @BDB_REQ = qw( |
117 | our @BDB_REQ = qw( |
80 | db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect |
118 | db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect |
81 | db_env_memp_sync db_env_memp_trickle |
119 | db_env_memp_sync db_env_memp_trickle |
82 | db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range |
120 | db_open db_close db_compact db_sync db_upgrade |
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121 | db_put db_get db_pget db_del db_key_range |
83 | db_txn_commit db_txn_abort db_txn_finish |
122 | db_txn_commit db_txn_abort db_txn_finish |
84 | db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del |
123 | db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del |
85 | db_sequence_open db_sequence_close |
124 | db_sequence_open db_sequence_close |
86 | db_sequence_get db_sequence_remove |
125 | db_sequence_get db_sequence_remove |
87 | ); |
126 | ); |
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99 | |
138 | |
100 | =head2 BERKELEYDB FUNCTIONS |
139 | =head2 BERKELEYDB FUNCTIONS |
101 | |
140 | |
102 | All of these are functions. The create functions simply return a new |
141 | All of these are functions. The create functions simply return a new |
103 | object and never block. All the remaining functions all take an optional |
142 | object and never block. All the remaining functions all take an optional |
104 | callback as last argument. If it is missing, then the fucntion will be |
143 | callback as last argument. If it is missing, then the function will be |
105 | executed synchronously. |
144 | executed synchronously. In both cases, C<$!> will reflect the return value |
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145 | of the function. |
106 | |
146 | |
107 | BDB functions that cannot block (mostly functions that manipulate |
147 | BDB functions that cannot block (mostly functions that manipulate |
108 | settings) are method calls on the relevant objects, so the rule of thumb |
148 | 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 |
149 | is: if its a method, its not blocking, if its a function, it takes a |
110 | callback as last argument. |
150 | callback as last argument. |
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145 | |
185 | |
146 | db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) |
186 | db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring 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 |
187 | 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) |
188 | db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
149 | flags: DB_NOSYNC |
189 | flags: DB_NOSYNC |
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190 | db_upgrade (DB *db, octetstring 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) |
191 | 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 |
192 | flags: FREELIST_ONLY FREE_SPACE |
152 | db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
193 | 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) |
194 | 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) |
195 | db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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242 | $int = $env->set_lk_max_lockers (U32 max) |
283 | $int = $env->set_lk_max_lockers (U32 max) |
243 | $int = $env->set_lk_max_locks (U32 max) |
284 | $int = $env->set_lk_max_locks (U32 max) |
244 | $int = $env->set_lk_max_objects (U32 max) |
285 | $int = $env->set_lk_max_objects (U32 max) |
245 | $int = $env->set_lg_bsize (U32 max) |
286 | $int = $env->set_lg_bsize (U32 max) |
246 | $int = $env->set_lg_max (U32 max) |
287 | $int = $env->set_lg_max (U32 max) |
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288 | $int = $env->mutex_set_increment (U32 increment) |
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289 | $int = $env->mutex_set_tas_spins (U32 tas_spins) |
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290 | $int = $env->mutex_set_max (U32 max) |
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291 | $int = $env->mutex_set_align (U32 align) |
247 | |
292 | |
248 | $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) |
293 | $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 |
294 | flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC |
250 | |
295 | |
251 | =head4 Example: |
296 | =head4 Example: |
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346 | DESTROY (DBC_ornull *dbc) |
391 | DESTROY (DBC_ornull *dbc) |
347 | CODE: |
392 | CODE: |
348 | if (dbc) |
393 | if (dbc) |
349 | dbc->c_close (dbc); |
394 | dbc->c_close (dbc); |
350 | |
395 | |
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396 | $int = $cursor->set_priority ($priority = PRIORITY_*) |
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397 | |
351 | =head4 Example: |
398 | =head4 Example: |
352 | |
399 | |
353 | my $c = $db->cursor; |
400 | my $c = $db->cursor; |
354 | |
401 | |
355 | for (;;) { |
402 | for (;;) { |
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388 | |
435 | |
389 | =head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION |
436 | =head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION |
390 | |
437 | |
391 | =over 4 |
438 | =over 4 |
392 | |
439 | |
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440 | =item $msg = BDB::strerror [$errno] |
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441 | |
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442 | Returns the string corresponding to the given errno value. If no argument |
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443 | is given, use C<$!>. |
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444 | |
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445 | Note that the BDB module also patches the C<$!> variable directly, so you |
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446 | should be able to get a bdb error string by simply stringifying C<$!>. |
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447 | |
393 | =item $fileno = BDB::poll_fileno |
448 | =item $fileno = BDB::poll_fileno |
394 | |
449 | |
395 | Return the I<request result pipe file descriptor>. This filehandle must be |
450 | 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 |
451 | 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 |
452 | 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 |
490 | interactiveness when perl is not fast enough to process all requests in |
436 | time. |
491 | time. |
437 | |
492 | |
438 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
493 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
439 | |
494 | |
440 | Example: Install an Event watcher that automatically calls |
495 | Example: Install an EV watcher that automatically calls |
441 | BDB::poll_cb with low priority, to ensure that other parts of the |
496 | BDB::poll_cb with low priority, to ensure that other parts of the |
442 | program get the CPU sometimes even under high AIO load. |
497 | program get the CPU sometimes even under high load. |
443 | |
498 | |
444 | # try not to spend much more than 0.1s in poll_cb |
499 | # try not to spend much more than 0.1s in poll_cb |
445 | BDB::max_poll_time 0.1; |
500 | BDB::max_poll_time 0.1; |
446 | |
501 | |
447 | # use a low priority so other tasks have priority |
502 | 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 | |
503 | |
452 | =item BDB::poll_wait |
504 | =item BDB::poll_wait |
453 | |
505 | |
454 | If there are any outstanding requests and none of them in the result |
506 | 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 |
507 | phase, wait till the result filehandle becomes ready for reading (simply |
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467 | |
519 | |
468 | BDB::poll_wait, BDB::poll_cb |
520 | BDB::poll_wait, BDB::poll_cb |
469 | |
521 | |
470 | =item BDB::flush |
522 | =item BDB::flush |
471 | |
523 | |
472 | Wait till all outstanding AIO requests have been handled. |
524 | Wait till all outstanding BDB requests have been handled. |
473 | |
525 | |
474 | Strictly equivalent to: |
526 | Strictly equivalent to: |
475 | |
527 | |
476 | BDB::poll_wait, BDB::poll_cb |
528 | BDB::poll_wait, BDB::poll_cb |
477 | while BDB::nreqs; |
529 | while BDB::nreqs; |
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482 | |
534 | |
483 | =over 4 |
535 | =over 4 |
484 | |
536 | |
485 | =item BDB::min_parallel $nthreads |
537 | =item BDB::min_parallel $nthreads |
486 | |
538 | |
487 | Set the minimum number of AIO threads to C<$nthreads>. The current |
539 | Set the minimum number of BDB threads to C<$nthreads>. The current |
488 | default is C<8>, which means eight asynchronous operations can execute |
540 | default is C<8>, which means eight asynchronous operations can execute |
489 | concurrently at any one time (the number of outstanding requests, |
541 | concurrently at any one time (the number of outstanding requests, |
490 | however, is unlimited). |
542 | however, is unlimited). |
491 | |
543 | |
492 | BDB starts threads only on demand, when an AIO request is queued and |
544 | 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 |
545 | 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 |
546 | 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. |
547 | is in the cache and could have been processed faster by a single thread. |
496 | |
548 | |
497 | It is recommended to keep the number of threads relatively low, as some |
549 | It is recommended to keep the number of threads relatively low, as some |
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502 | Under most circumstances you don't need to call this function, as the |
554 | 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. |
555 | module selects a default that is suitable for low to moderate load. |
504 | |
556 | |
505 | =item BDB::max_parallel $nthreads |
557 | =item BDB::max_parallel $nthreads |
506 | |
558 | |
507 | Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
559 | Sets the maximum number of BDB threads to C<$nthreads>. If more than the |
508 | specified number of threads are currently running, this function kills |
560 | specified number of threads are currently running, this function kills |
509 | them. This function blocks until the limit is reached. |
561 | them. This function blocks until the limit is reached. |
510 | |
562 | |
511 | While C<$nthreads> are zero, aio requests get queued but not executed |
563 | While C<$nthreads> are zero, aio requests get queued but not executed |
512 | until the number of threads has been increased again. |
564 | until the number of threads has been increased again. |
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615 | |
667 | |
616 | =head2 FORK BEHAVIOUR |
668 | =head2 FORK BEHAVIOUR |
617 | |
669 | |
618 | This module should do "the right thing" when the process using it forks: |
670 | This module should do "the right thing" when the process using it forks: |
619 | |
671 | |
620 | Before the fork, IO::AIO enters a quiescent state where no requests |
672 | 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 |
673 | 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 |
674 | the fork the parent simply leaves the quiescent state and continues |
623 | request/result processing, while the child frees the request/result queue |
675 | 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 |
676 | (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 |
677 | parent). Threads will be started on demand until the limit set in the |
626 | parent process has been reached again. |
678 | parent process has been reached again. |
627 | |
679 | |
628 | In short: the parent will, after a short pause, continue as if fork had |
680 | 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 |
681 | not been called, while the child will act as if BDB has not been used |
630 | yet. |
682 | yet. |
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683 | |
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684 | Win32 note: there is no fork on win32, and perls emulation of it is too |
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685 | broken to be supported, so do not use BDB in a windows pseudo-fork, better |
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686 | yet, switch to a more capable platform. |
631 | |
687 | |
632 | =head2 MEMORY USAGE |
688 | =head2 MEMORY USAGE |
633 | |
689 | |
634 | Per-request usage: |
690 | Per-request usage: |
635 | |
691 | |
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657 | TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, |
713 | TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, |
658 | above. |
714 | above. |
659 | |
715 | |
660 | =head1 SEE ALSO |
716 | =head1 SEE ALSO |
661 | |
717 | |
662 | L<Coro::AIO>. |
718 | L<Coro::BDB>, L<IO::AIO>. |
663 | |
719 | |
664 | =head1 AUTHOR |
720 | =head1 AUTHOR |
665 | |
721 | |
666 | Marc Lehmann <schmorp@schmorp.de> |
722 | Marc Lehmann <schmorp@schmorp.de> |
667 | http://home.schmorp.de/ |
723 | http://home.schmorp.de/ |