[ViewVC] Diff of: cvs/BDB/BDB.pm

Comparing BDB/BDB.pm (file contents):
Revision 1.4 by root, Mon Feb 5 23:46:15 2007 UTC vs.
Revision 1.37 by root, Mon Jul 7 14:28:53 2008 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use BDB;	7	use BDB;
8		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 intergration 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
		45
9	=head1 DESCRIPTION	46	=head1 DESCRIPTION
10		47
11	=head2 EXAMPLE	48	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
		49	The BDB API is very similar to the C API (the translation has been very faithful).
		50
		51	See also the example sections in the document below and possibly the eg/
		52	subdirectory of the BDB distribution. Last not least see the IO::AIO
		53	documentation, as that module uses almost the same asynchronous request
		54	model as this module.
		55
		56	I know this is woefully inadequate documentation. Send a patch!
		57
12		58
13	=head1 REQUEST ANATOMY AND LIFETIME	59	=head1 REQUEST ANATOMY AND LIFETIME
14		60
15	Every request method creates a request. which is a C data structure not	61	Every request method creates a request. which is a C data structure not
16	directly visible to Perl.	62	directly visible to Perl.
…		…
63	use strict 'vars';	109	use strict 'vars';
64		110
65	use base 'Exporter';	111	use base 'Exporter';
66		112
67	BEGIN {	113	BEGIN {
68	our $VERSION = '0.1';	114	our $VERSION = '1.5';
69		115
70	our @BDB_REQ = qw(	116	our @BDB_REQ = qw(
71	db_env_create db_env_open db_env_close	117	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		118	db_env_memp_sync db_env_memp_trickle
72	db_create db_open db_close db_compact db_sync db_put db_get db_pget	119	db_open db_close db_compact db_sync db_upgrade
		120	db_put db_get db_pget db_del db_key_range
73	db_txn_commit db_txn_abort	121	db_txn_commit db_txn_abort db_txn_finish
		122	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		123	db_sequence_open db_sequence_close
		124	db_sequence_get db_sequence_remove
74	);	125	);
75	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice));	126	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		127	our @EXPORT_OK = qw(
76	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	128	poll_fileno poll_cb poll_wait flush
77	min_parallel max_parallel max_idle	129	min_parallel max_parallel max_idle
78	nreqs nready npending nthreads	130	nreqs nready npending nthreads
79	max_poll_time max_poll_reqs);	131	max_poll_time max_poll_reqs
		132	);
80		133
81	require XSLoader;	134	require XSLoader;
82	XSLoader::load ("BDB", $VERSION);	135	XSLoader::load ("BDB", $VERSION);
83	}	136	}
84		137
		138	=head2 WIN32 FILENAMES/DATABASE NAME MESS
		139
		140	Perl on Win32 supports only ASCII filenames (the reason is that it abuses
		141	an internal flag to store wether a filename is Unicode or ANSI, but that
		142	flag is used for somethign else in the perl core, so there is no way to
		143	detect wether a filename is ANSI or Unicode-encoded). The BDB module
		144	tries to work around this issue by assuming that the filename is an ANSI
		145	filename and BDB was built for unicode support.
		146
		147	=head2 BERKELEYDB FUNCTIONS
		148
		149	All of these are functions. The create functions simply return a new
		150	object and never block. All the remaining functions take an optional
		151	callback as last argument. If it is missing, then the function will be
		152	executed synchronously. In both cases, C<$!> will reflect the return value
		153	of the function.
		154
		155	BDB functions that cannot block (mostly functions that manipulate
		156	settings) are method calls on the relevant objects, so the rule of thumb
		157	is: if it's a method, it's not blocking, if it's a function, it takes a
		158	callback as last argument.
		159
		160	In the following, C<$int> signifies an integer return value,
		161	C<octetstring> is a "binary string" (i.e. a perl string with no character
		162	indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
		163	integer, C<NV> is a floating point value.
		164
		165	The C<SV *> types are generic perl scalars (for input and output of data
		166	values), and the C<SV *callback> is the optional callback function to call
		167	when the request is completed.
		168
		169	The various C<DB_ENV> etc. arguments are handles return by
		170	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		171	appended C<_ornull> this means they are optional and you can pass C<undef>
		172	for them, resulting a NULL pointer on the C level.
		173
		174	=head3 BDB functions
		175
		176	Functions in the BDB namespace, exported by default:
		177
		178	$env = db_env_create (U32 env_flags = 0)
		179	flags: RPCCLIENT
		180
		181	db_env_open (DB_ENV env, octetstring db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		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
		183	db_env_close (DB_ENV env, 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)
		185	flags: FORCE
		186	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		187	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		188	db_env_memp_sync (DB_ENV env, 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)
		190
		191	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		192	flags: XA_CREATE
		193
		194	db_open (DB db, DB_TXN_ornull txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		195	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		196	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		197	flags: DB_NOSYNC
		198	db_upgrade (DB db, octetstring file, U32 flags = 0, SV callback = &PL_sv_undef)
		199	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)
		200	flags: FREELIST_ONLY FREE_SPACE
		201	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		202	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		203	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		204	flags: APPEND NODUPDATA NOOVERWRITE
		205	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		206	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		207	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		208	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		209	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		210	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		211	flags: TXN_NOSYNC TXN_SYNC
		212	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		213
		214	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		215	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		216	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		217	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		218	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		219	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
		220	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		221	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		222
		223	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		224	flags: CREATE EXCL
		225	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		226	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)
		227	flags: TXN_NOSYNC
		228	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		229	flags: TXN_NOSYNC
		230
		231	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		232
		233	This is not actually a Berkeley DB function but a BDB module
		234	extension. The background for this exytension is: It is very annoying to
		235	have to check every single BDB function for error returns and provide a
		236	codepath out of your transaction. While the BDB module still makes this
		237	possible, it contains the following extensions:
		238
		239	When a transaction-protected function returns any operating system
		240	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		241	transaction. This flag is also set by Berkeley DB functions themselves
		242	when an operation fails with LOCK_DEADLOCK, and it causes all further
		243	operations on that transaction (including C<db_txn_commit>) to fail.
		244
		245	The C<db_txn_finish> request will look at this flag, and, if it is set,
		246	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		247	if it isn't set to something else yet). If it isn't set, it will call
		248	C<db_txn_commit> and return the error normally.
		249
		250	How to use this? Easy: just write your transaction normally:
		251
		252	my $txn = $db_env->txn_begin;
		253	db_get $db, $txn, "key", my $data;
		254	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		255	db_txn_finish $txn;
		256	die "transaction failed" if $!;
		257
		258	That is, handle only the expected errors. If something unexpected happens
		259	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		260	requests (db_put in this case) will simply be skipped (they will fail with
		261	LOCK_DEADLOCK) and the transaction will be aborted.
		262
		263	You can use the C<< $txn->failed >> method to check wether a transaction
		264	has failed in this way and abort further processing (excluding
		265	C<db_txn_finish>).
		266
		267	=head3 DB_ENV/database environment methods
		268
		269	Methods available on DB_ENV/$env handles:
		270
		271	DESTROY (DB_ENV_ornull *env)
		272	CODE:
		273	if (env)
		274	env->close (env, 0);
		275
		276	$int = $env->set_data_dir (const char *dir)
		277	$int = $env->set_tmp_dir (const char *dir)
		278	$int = $env->set_lg_dir (const char *dir)
		279	$int = $env->set_shm_key (long shm_key)
		280	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		281	$int = $env->set_flags (U32 flags, int onoff)
		282	$env->set_errfile (FILE *errfile = 0)
		283	$env->set_msgfile (FILE *msgfile = 0)
		284	$int = $env->set_verbose (U32 which, int onoff = 1)
		285	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		286	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		287	$int = $env->set_mp_max_openfd (int maxopenfd);
		288	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		289	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		290	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		291	$int = $env->set_lk_max_lockers (U32 max)
		292	$int = $env->set_lk_max_locks (U32 max)
		293	$int = $env->set_lk_max_objects (U32 max)
		294	$int = $env->set_lg_bsize (U32 max)
		295	$int = $env->set_lg_max (U32 max)
		296	$int = $env->mutex_set_increment (U32 increment)
		297	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		298	$int = $env->mutex_set_max (U32 max)
		299	$int = $env->mutex_set_align (U32 align)
		300
		301	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		302	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		303
		304	=head4 Example:
		305
		306	use AnyEvent;
		307	use BDB;
		308
		309	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		310	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		311
		312	BDB::min_parallel 8;
		313
		314	my $env = db_env_create;
		315
		316	mkdir "bdtest", 0700;
		317	db_env_open
		318	$env,
		319	"bdtest",
		320	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		321	0600;
		322
		323	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		324
		325
		326	=head3 DB/database methods
		327
		328	Methods available on DB/$db handles:
		329
		330	DESTROY (DB_ornull *db)
		331	CODE:
		332	if (db)
		333	{
		334	SV env = (SV )db->app_private;
		335	db->close (db, 0);
		336	SvREFCNT_dec (env);
		337	}
		338
		339	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		340	$int = $db->set_flags (U32 flags)
		341	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		342	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		343	Hash: DUP DUPSORT
		344	Queue: INORDER
		345	Recno: RENUMBER SNAPSHOT
		346
		347	$int = $db->set_encrypt (const char *password, U32 flags)
		348	$int = $db->set_lorder (int lorder)
		349	$int = $db->set_bt_minkey (U32 minkey)
		350	$int = $db->set_re_delim (int delim)
		351	$int = $db->set_re_pad (int re_pad)
		352	$int = $db->set_re_source (char *source)
		353	$int = $db->set_re_len (U32 re_len)
		354	$int = $db->set_h_ffactor (U32 h_ffactor)
		355	$int = $db->set_h_nelem (U32 h_nelem)
		356	$int = $db->set_q_extentsize (U32 extentsize)
		357
		358	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		359	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		360	$seq = $db->sequence (U32 flags = 0)
		361
		362	=head4 Example:
		363
		364	my $db = db_create $env;
		365	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		366
		367	for (1..1000) {
		368	db_put $db, undef, "key $_", "data $_";
		369
		370	db_key_range $db, undef, "key $_", my $keyrange;
		371	my ($lt, $eq, $gt) = @$keyrange;
		372	}
		373
		374	db_del $db, undef, "key $_" for 1..1000;
		375
		376	db_sync $db;
		377
		378
		379	=head3 DB_TXN/transaction methods
		380
		381	Methods available on DB_TXN/$txn handles:
		382
		383	DESTROY (DB_TXN_ornull *txn)
		384	CODE:
		385	if (txn)
		386	txn->abort (txn);
		387
		388	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		389	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		390
		391	$bool = $txn->failed
		392	# see db_txn_finish documentation, above
		393
		394
		395	=head3 DBC/cursor methods
		396
		397	Methods available on DBC/$dbc handles:
		398
		399	DESTROY (DBC_ornull *dbc)
		400	CODE:
		401	if (dbc)
		402	dbc->c_close (dbc);
		403
		404	$int = $cursor->set_priority ($priority = PRIORITY_*)
		405
		406	=head4 Example:
		407
		408	my $c = $db->cursor;
		409
		410	for (;;) {
		411	db_c_get $c, my $key, my $data, BDB::NEXT;
		412	warn "<$!,$key,$data>";
		413	last if $!;
		414	}
		415
		416	db_c_close $c;
		417
		418
		419	=head3 DB_SEQUENCE/sequence methods
		420
		421	Methods available on DB_SEQUENCE/$seq handles:
		422
		423	DESTROY (DB_SEQUENCE_ornull *seq)
		424	CODE:
		425	if (seq)
		426	seq->close (seq, 0);
		427
		428	$int = $seq->initial_value (db_seq_t value)
		429	$int = $seq->set_cachesize (U32 size)
		430	$int = $seq->set_flags (U32 flags)
		431	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		432	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		433
		434	=head4 Example:
		435
		436	my $seq = $db->sequence;
		437
		438	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		439	db_sequence_get $seq, undef, 1, my $value;
		440
		441
85	=head2 SUPPORT FUNCTIONS	442	=head2 SUPPORT FUNCTIONS
86		443
87	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	444	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
88		445
89	=over 4	446	=over 4
		447
		448	=item $msg = BDB::strerror [$errno]
		449
		450	Returns the string corresponding to the given errno value. If no argument
		451	is given, use C<$!>.
		452
		453	Note that the BDB module also patches the C<$!> variable directly, so you
		454	should be able to get a bdb error string by simply stringifying C<$!>.
90		455
91	=item $fileno = BDB::poll_fileno	456	=item $fileno = BDB::poll_fileno
92		457
93	Return the I<request result pipe file descriptor>. This filehandle must be	458	Return the I<request result pipe file descriptor>. This filehandle must be
94	polled for reading by some mechanism outside this module (e.g. Event or	459	polled for reading by some mechanism outside this module (e.g. Event or
…		…
133	interactiveness when perl is not fast enough to process all requests in	498	interactiveness when perl is not fast enough to process all requests in
134	time.	499	time.
135		500
136	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	501	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
137		502
138	Example: Install an Event watcher that automatically calls	503	Example: Install an EV watcher that automatically calls
139	BDB::poll_cb with low priority, to ensure that other parts of the	504	BDB::poll_cb with low priority, to ensure that other parts of the
140	program get the CPU sometimes even under high AIO load.	505	program get the CPU sometimes even under high load.
141		506
142	# try not to spend much more than 0.1s in poll_cb	507	# try not to spend much more than 0.1s in poll_cb
143	BDB::max_poll_time 0.1;	508	BDB::max_poll_time 0.1;
144		509
145	# use a low priority so other tasks have priority	510	my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
146	Event->io (fd => BDB::poll_fileno,
147	poll => 'r', nice => 1,
148	cb => &BDB::poll_cb);
149		511
150	=item BDB::poll_wait	512	=item BDB::poll_wait
151		513
152	If there are any outstanding requests and none of them in the result	514	If there are any outstanding requests and none of them in the result
153	phase, wait till the result filehandle becomes ready for reading (simply	515	phase, wait till the result filehandle becomes ready for reading (simply
…		…
165		527
166	BDB::poll_wait, BDB::poll_cb	528	BDB::poll_wait, BDB::poll_cb
167		529
168	=item BDB::flush	530	=item BDB::flush
169		531
170	Wait till all outstanding AIO requests have been handled.	532	Wait till all outstanding BDB requests have been handled.
171		533
172	Strictly equivalent to:	534	Strictly equivalent to:
173		535
174	BDB::poll_wait, BDB::poll_cb	536	BDB::poll_wait, BDB::poll_cb
175	while BDB::nreqs;	537	while BDB::nreqs;
176		538
		539	=back
		540
177	=head3 CONTROLLING THE NUMBER OF THREADS	541	=head3 CONTROLLING THE NUMBER OF THREADS
178		542
		543	=over 4
		544
179	=item BDB::min_parallel $nthreads	545	=item BDB::min_parallel $nthreads
180		546
181	Set the minimum number of AIO threads to C<$nthreads>. The current	547	Set the minimum number of BDB threads to C<$nthreads>. The current
182	default is C<8>, which means eight asynchronous operations can execute	548	default is C<8>, which means eight asynchronous operations can execute
183	concurrently at any one time (the number of outstanding requests,	549	concurrently at any one time (the number of outstanding requests,
184	however, is unlimited).	550	however, is unlimited).
185		551
186	BDB starts threads only on demand, when an AIO request is queued and	552	BDB starts threads only on demand, when an BDB request is queued and
187	no free thread exists. Please note that queueing up a hundred requests can	553	no free thread exists. Please note that queueing up a hundred requests can
188	create demand for a hundred threads, even if it turns out that everything	554	create demand for a hundred threads, even if it turns out that everything
189	is in the cache and could have been processed faster by a single thread.	555	is in the cache and could have been processed faster by a single thread.
190		556
191	It is recommended to keep the number of threads relatively low, as some	557	It is recommended to keep the number of threads relatively low, as some
…		…
196	Under most circumstances you don't need to call this function, as the	562	Under most circumstances you don't need to call this function, as the
197	module selects a default that is suitable for low to moderate load.	563	module selects a default that is suitable for low to moderate load.
198		564
199	=item BDB::max_parallel $nthreads	565	=item BDB::max_parallel $nthreads
200		566
201	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	567	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
202	specified number of threads are currently running, this function kills	568	specified number of threads are currently running, this function kills
203	them. This function blocks until the limit is reached.	569	them. This function blocks until the limit is reached.
204		570
205	While C<$nthreads> are zero, aio requests get queued but not executed	571	While C<$nthreads> are zero, aio requests get queued but not executed
206	until the number of threads has been increased again.	572	until the number of threads has been increased again.
…		…
245		611
246	=item BDB::set_sync_prepare $cb	612	=item BDB::set_sync_prepare $cb
247		613
248	Sets a callback that is called whenever a request is created without an	614	Sets a callback that is called whenever a request is created without an
249	explicit callback. It has to return two code references. The first is used	615	explicit callback. It has to return two code references. The first is used
250	as the request callback, and the second is called to wait until the first	616	as the request callback (it should save the return status), and the second
		617	is called to wait until the first callback has been called (it must set
		618	C<$!> to the return status).
		619
		620	This mechanism can be used to include BDB into other event mechanisms,
		621	such as L<AnyEvent::BDB> or L<Coro::BDB>.
		622
251	callback has been called. The default implementation works like this:	623	The default implementation works like this:
252		624
253	sub {	625	sub {
254	my $status;	626	my $status;
255	(	627	(
256	sub { $status = $! },	628	sub { $status = $! },
257	sub { BDB::poll while !defined $status; $! = $status },	629	sub { BDB::poll while !defined $status; $! = $status },
258	)	630	)
259	}	631	}
		632
		633	It simply blocks the process till the request has finished and then sets
		634	C<$!> to the return value. This means that if you don't use a callback,
		635	BDB will simply fall back to synchronous operations.
260		636
261	=back	637	=back
262		638
263	=head3 STATISTICAL INFORMATION	639	=head3 STATISTICAL INFORMATION
264		640
…		…
309		685
310	=head2 FORK BEHAVIOUR	686	=head2 FORK BEHAVIOUR
311		687
312	This module should do "the right thing" when the process using it forks:	688	This module should do "the right thing" when the process using it forks:
313		689
314	Before the fork, IO::AIO enters a quiescent state where no requests	690	Before the fork, BDB enters a quiescent state where no requests
315	can be added in other threads and no results will be processed. After	691	can be added in other threads and no results will be processed. After
316	the fork the parent simply leaves the quiescent state and continues	692	the fork the parent simply leaves the quiescent state and continues
317	request/result processing, while the child frees the request/result queue	693	request/result processing, while the child frees the request/result queue
318	(so that the requests started before the fork will only be handled in the	694	(so that the requests started before the fork will only be handled in the
319	parent). Threads will be started on demand until the limit set in the	695	parent). Threads will be started on demand until the limit set in the
320	parent process has been reached again.	696	parent process has been reached again.
321		697
322	In short: the parent will, after a short pause, continue as if fork had	698	In short: the parent will, after a short pause, continue as if fork had
323	not been called, while the child will act as if IO::AIO has not been used	699	not been called, while the child will act as if BDB has not been used
324	yet.	700	yet.
		701
		702	Win32 note: there is no fork on win32, and perls emulation of it is too
		703	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		704	yet, switch to a more capable platform.
325		705
326	=head2 MEMORY USAGE	706	=head2 MEMORY USAGE
327		707
328	Per-request usage:	708	Per-request usage:
329		709
…		…
331	bytes of memory. In addition, stat requests need a stat buffer (possibly	711	bytes of memory. In addition, stat requests need a stat buffer (possibly
332	a few hundred bytes), readdir requires a result buffer and so on. Perl	712	a few hundred bytes), readdir requires a result buffer and so on. Perl
333	scalars and other data passed into aio requests will also be locked and	713	scalars and other data passed into aio requests will also be locked and
334	will consume memory till the request has entered the done state.	714	will consume memory till the request has entered the done state.
335		715
336	This is now awfully much, so queuing lots of requests is not usually a	716	This is not awfully much, so queuing lots of requests is not usually a
337	problem.	717	problem.
338		718
339	Per-thread usage:	719	Per-thread usage:
340		720
341	In the execution phase, some aio requests require more memory for	721	In the execution phase, some aio requests require more memory for
342	temporary buffers, and each thread requires a stack and other data	722	temporary buffers, and each thread requires a stack and other data
343	structures (usually around 16k-128k, depending on the OS).	723	structures (usually around 16k-128k, depending on the OS).
344		724
345	=head1 KNOWN BUGS	725	=head1 KNOWN BUGS
346		726
347	Known bugs will be fixed in the next release.	727	Known bugs will be fixed in the next release, except:
		728
		729	If you use a transaction in any request, and the request returns
		730	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		731	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		732	above.
348		733
349	=head1 SEE ALSO	734	=head1 SEE ALSO
350		735
351	L<Coro::AIO>.	736	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		737	syntax), L<IO::AIO> (nice to have).
352		738
353	=head1 AUTHOR	739	=head1 AUTHOR
354		740
355	Marc Lehmann <schmorp@schmorp.de>	741	Marc Lehmann <schmorp@schmorp.de>
356	http://home.schmorp.de/	742	http://home.schmorp.de/

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Comparing BDB/BDB.pm (file contents): Revision 1.4 by root, Mon Feb 5 23:46:15 2007 UTC vs. Revision 1.37 by root, Mon Jul 7 14:28:53 2008 UTC

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Comparing BDB/BDB.pm (file contents):
Revision 1.4 by root, Mon Feb 5 23:46:15 2007 UTC vs.
Revision 1.37 by root, Mon Jul 7 14:28:53 2008 UTC