[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 1.43 by root, Wed Jul 9 21:00:13 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 = '1.7';
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 db_env_dbrename db_env_dbremove
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<bdb_filename> is a "filename" (octets on unix, madness on windows),
		162	C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
		163	floating point value.
		164
		165	Most C<SV *> types are generic perl scalars (for input and output of data
		166	values).
		167
		168	The various C<DB_ENV> etc. arguments are handles return by
		169	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		170	appended C<_ornull> this means they are optional and you can pass C<undef>
		171	for them, resulting a NULL pointer on the C level.
		172
		173	The C<SV *callback> is the optional callback function to call when the
		174	request is completed. This last callback argument is special: the callback
		175	is simply the last argument passed. If there are "optional" arguments
		176	before the callback they can be left out. The callback itself can be left
		177	out or specified as C<undef>, in which case the function will be executed
		178	synchronously.
		179
		180	For example, C<db_env_txn_checkpoint> usually is called with all integer
		181	arguments zero. These can be left out, so all of these specify a call
		182	to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
		183	callback to be called:
		184
		185	db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
		186	db_env_txn_checkpoint $db_env, 0, 0, sub { };
		187	db_env_txn_checkpoint $db_env, sub { };
		188
		189	While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
		190	executed synchronously:
		191
		192	db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
		193	db_env_txn_checkpoint $db_env, 0, 0, 0;
		194	db_env_txn_checkpoint $db_env, 0;
		195
		196	=head3 BDB functions
		197
		198	Functions in the BDB namespace, exported by default:
		199
		200	$env = db_env_create (U32 env_flags = 0)
		201	flags: RPCCLIENT
		202
		203	db_env_open (DB_ENV env, bdb_filename db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		204	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
		205	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		206	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		207	flags: FORCE
		208	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		209	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		210	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		211	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		212	db_env_dbremove (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
		213	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)
		214
		215	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		216	flags: XA_CREATE
		217
		218	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)
		219	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		220	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		221	flags: DB_NOSYNC
		222	db_upgrade (DB db, bdb_filename file, U32 flags = 0, SV callback = &PL_sv_undef)
		223	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)
		224	flags: FREELIST_ONLY FREE_SPACE
		225	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		226	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		227	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		228	flags: APPEND NODUPDATA NOOVERWRITE
		229	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		230	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		231	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		232	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		233	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		234	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		235	flags: TXN_NOSYNC TXN_SYNC
		236	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		237
		238	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		239	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		240	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		241	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		242	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		243	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
		244	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		245	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		246
		247	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		248	flags: CREATE EXCL
		249	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		250	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)
		251	flags: TXN_NOSYNC
		252	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		253	flags: TXN_NOSYNC
		254
		255	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		256
		257	This is not actually a Berkeley DB function but a BDB module
		258	extension. The background for this exytension is: It is very annoying to
		259	have to check every single BDB function for error returns and provide a
		260	codepath out of your transaction. While the BDB module still makes this
		261	possible, it contains the following extensions:
		262
		263	When a transaction-protected function returns any operating system
		264	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		265	transaction. This flag is also set by Berkeley DB functions themselves
		266	when an operation fails with LOCK_DEADLOCK, and it causes all further
		267	operations on that transaction (including C<db_txn_commit>) to fail.
		268
		269	The C<db_txn_finish> request will look at this flag, and, if it is set,
		270	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		271	if it isn't set to something else yet). If it isn't set, it will call
		272	C<db_txn_commit> and return the error normally.
		273
		274	How to use this? Easy: just write your transaction normally:
		275
		276	my $txn = $db_env->txn_begin;
		277	db_get $db, $txn, "key", my $data;
		278	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		279	db_txn_finish $txn;
		280	die "transaction failed" if $!;
		281
		282	That is, handle only the expected errors. If something unexpected happens
		283	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		284	requests (db_put in this case) will simply be skipped (they will fail with
		285	LOCK_DEADLOCK) and the transaction will be aborted.
		286
		287	You can use the C<< $txn->failed >> method to check wether a transaction
		288	has failed in this way and abort further processing (excluding
		289	C<db_txn_finish>).
		290
		291	=head3 DB_ENV/database environment methods
		292
		293	Methods available on DB_ENV/$env handles:
		294
		295	DESTROY (DB_ENV_ornull *env)
		296	CODE:
		297	if (env)
		298	env->close (env, 0);
		299
		300	$int = $env->set_data_dir (const char *dir)
		301	$int = $env->set_tmp_dir (const char *dir)
		302	$int = $env->set_lg_dir (const char *dir)
		303	$int = $env->set_shm_key (long shm_key)
		304	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		305	$int = $env->set_flags (U32 flags, int onoff = 1)
		306	$int = $env->log_set_config (U32 flags, int onoff = 1) [v4.7]
		307	$int = $env->set_intermediate_dir_mode (const char *modestring) [v4.7]
		308	$env->set_errfile (FILE *errfile = 0)
		309	$env->set_msgfile (FILE *msgfile = 0)
		310	$int = $env->set_verbose (U32 which, int onoff = 1)
		311	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		312	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		313	$int = $env->set_mp_max_openfd (int maxopenfd);
		314	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		315	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		316	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		317	$int = $env->set_lk_max_lockers (U32 max)
		318	$int = $env->set_lk_max_locks (U32 max)
		319	$int = $env->set_lk_max_objects (U32 max)
		320	$int = $env->set_lg_bsize (U32 max)
		321	$int = $env->set_lg_max (U32 max)
		322	$int = $env->mutex_set_increment (U32 increment)
		323	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		324	$int = $env->mutex_set_max (U32 max)
		325	$int = $env->mutex_set_align (U32 align)
		326
		327	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		328	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		329	$txn = $env->cdsgroup_begin;
		330
		331	=head4 Example:
		332
		333	use AnyEvent;
		334	use BDB;
		335
		336	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		337	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		338
		339	BDB::min_parallel 8;
		340
		341	my $env = db_env_create;
		342
		343	mkdir "bdtest", 0700;
		344	db_env_open
		345	$env,
		346	"bdtest",
		347	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		348	0600;
		349
		350	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		351
		352
		353	=head3 DB/database methods
		354
		355	Methods available on DB/$db handles:
		356
		357	DESTROY (DB_ornull *db)
		358	CODE:
		359	if (db)
		360	{
		361	SV env = (SV )db->app_private;
		362	db->close (db, 0);
		363	SvREFCNT_dec (env);
		364	}
		365
		366	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		367	$int = $db->set_flags (U32 flags)
		368	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		369	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		370	Hash: DUP DUPSORT
		371	Queue: INORDER
		372	Recno: RENUMBER SNAPSHOT
		373
		374	$int = $db->set_encrypt (const char *password, U32 flags)
		375	$int = $db->set_lorder (int lorder)
		376	$int = $db->set_bt_minkey (U32 minkey)
		377	$int = $db->set_re_delim (int delim)
		378	$int = $db->set_re_pad (int re_pad)
		379	$int = $db->set_re_source (char *source)
		380	$int = $db->set_re_len (U32 re_len)
		381	$int = $db->set_h_ffactor (U32 h_ffactor)
		382	$int = $db->set_h_nelem (U32 h_nelem)
		383	$int = $db->set_q_extentsize (U32 extentsize)
		384
		385	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		386	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		387	$seq = $db->sequence (U32 flags = 0)
		388
		389	=head4 Example:
		390
		391	my $db = db_create $env;
		392	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		393
		394	for (1..1000) {
		395	db_put $db, undef, "key $_", "data $_";
		396
		397	db_key_range $db, undef, "key $_", my $keyrange;
		398	my ($lt, $eq, $gt) = @$keyrange;
		399	}
		400
		401	db_del $db, undef, "key $_" for 1..1000;
		402
		403	db_sync $db;
		404
		405
		406	=head3 DB_TXN/transaction methods
		407
		408	Methods available on DB_TXN/$txn handles:
		409
		410	DESTROY (DB_TXN_ornull *txn)
		411	CODE:
		412	if (txn)
		413	txn->abort (txn);
		414
		415	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		416	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		417
		418	$bool = $txn->failed
		419	# see db_txn_finish documentation, above
		420
		421
		422	=head3 DBC/cursor methods
		423
		424	Methods available on DBC/$dbc handles:
		425
		426	DESTROY (DBC_ornull *dbc)
		427	CODE:
		428	if (dbc)
		429	dbc->c_close (dbc);
		430
		431	$int = $cursor->set_priority ($priority = PRIORITY_*)
		432
		433	=head4 Example:
		434
		435	my $c = $db->cursor;
		436
		437	for (;;) {
		438	db_c_get $c, my $key, my $data, BDB::NEXT;
		439	warn "<$!,$key,$data>";
		440	last if $!;
		441	}
		442
		443	db_c_close $c;
		444
		445
		446	=head3 DB_SEQUENCE/sequence methods
		447
		448	Methods available on DB_SEQUENCE/$seq handles:
		449
		450	DESTROY (DB_SEQUENCE_ornull *seq)
		451	CODE:
		452	if (seq)
		453	seq->close (seq, 0);
		454
		455	$int = $seq->initial_value (db_seq_t value)
		456	$int = $seq->set_cachesize (U32 size)
		457	$int = $seq->set_flags (U32 flags)
		458	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		459	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		460
		461	=head4 Example:
		462
		463	my $seq = $db->sequence;
		464
		465	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		466	db_sequence_get $seq, undef, 1, my $value;
		467
		468
85	=head2 SUPPORT FUNCTIONS	469	=head2 SUPPORT FUNCTIONS
86		470
87	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	471	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
88		472
89	=over 4	473	=over 4
		474
		475	=item $msg = BDB::strerror [$errno]
		476
		477	Returns the string corresponding to the given errno value. If no argument
		478	is given, use C<$!>.
		479
		480	Note that the BDB module also patches the C<$!> variable directly, so you
		481	should be able to get a bdb error string by simply stringifying C<$!>.
90		482
91	=item $fileno = BDB::poll_fileno	483	=item $fileno = BDB::poll_fileno
92		484
93	Return the I<request result pipe file descriptor>. This filehandle must be	485	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	486	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	525	interactiveness when perl is not fast enough to process all requests in
134	time.	526	time.
135		527
136	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	528	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
137		529
138	Example: Install an Event watcher that automatically calls	530	Example: Install an EV watcher that automatically calls
139	BDB::poll_cb with low priority, to ensure that other parts of the	531	BDB::poll_cb with low priority, to ensure that other parts of the
140	program get the CPU sometimes even under high AIO load.	532	program get the CPU sometimes even under high load.
141		533
142	# try not to spend much more than 0.1s in poll_cb	534	# try not to spend much more than 0.1s in poll_cb
143	BDB::max_poll_time 0.1;	535	BDB::max_poll_time 0.1;
144		536
145	# use a low priority so other tasks have priority	537	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		538
150	=item BDB::poll_wait	539	=item BDB::poll_wait
151		540
152	If there are any outstanding requests and none of them in the result	541	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	542	phase, wait till the result filehandle becomes ready for reading (simply
…		…
165		554
166	BDB::poll_wait, BDB::poll_cb	555	BDB::poll_wait, BDB::poll_cb
167		556
168	=item BDB::flush	557	=item BDB::flush
169		558
170	Wait till all outstanding AIO requests have been handled.	559	Wait till all outstanding BDB requests have been handled.
171		560
172	Strictly equivalent to:	561	Strictly equivalent to:
173		562
174	BDB::poll_wait, BDB::poll_cb	563	BDB::poll_wait, BDB::poll_cb
175	while BDB::nreqs;	564	while BDB::nreqs;
176		565
		566	=back
		567
		568	=head3 VERSION CHECKING
		569
		570	BerkeleyDB comes in various versions, many of them have minor
		571	incompatibilities. This means that traditional "at least version x.x"
		572	checks are often not sufficient.
		573
		574	Example: set the log_autoremove option in a way compatible with <v.47 and
		575	v4.7. Note the use of & on the constants to avoid triggering a compiletime
		576	bug when the symbol isn't available.
		577
		578	$DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
		579	$DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
		580
		581	=over 4
		582
		583	=item BDB::VERSION
		584
		585	The C<BDB::VERSION> function, when called without arguments, returns the
		586	Berkeley DB version as a v-string (usually with 3 components). You should
		587	use C<lt> and C<ge> operators exclusively to make comparisons.
		588
		589	Example: check for at least version 4.7.
		590
		591	BDB::VERSION ge v4.7 or die;
		592
		593	=item BDB::VERSION min-version
		594
		595	Returns true if the BDB version is at least the given version (specified
		596	as a v-string), false otherwise.
		597
		598	Example: check for at least version 4.5.
		599
		600	BDB::VERSION v4.7 or die;
		601
		602	=item BDB::VERSION min-version, max-version
		603
		604	Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
		605	and less then C<max-version>.
		606
		607	Example: check wether version is strictly less then v4.7.
		608
		609	BDB::VERSION v0, v4.7
		610	or die "version 4.7 is not yet supported";
		611
		612	=back
		613
		614	=cut
		615
		616	sub VERSION {
		617	if (@_ > 0) {
		618	return undef if VERSION_v lt $_[0];
		619	if (@_ > 1) {
		620	return undef if VERSION_v ge $_[1];
		621	}
		622	}
		623
		624	VERSION_v
		625	}
		626
177	=head3 CONTROLLING THE NUMBER OF THREADS	627	=head3 CONTROLLING THE NUMBER OF THREADS
178		628
		629	=over 4
		630
179	=item BDB::min_parallel $nthreads	631	=item BDB::min_parallel $nthreads
180		632
181	Set the minimum number of AIO threads to C<$nthreads>. The current	633	Set the minimum number of BDB threads to C<$nthreads>. The current
182	default is C<8>, which means eight asynchronous operations can execute	634	default is C<8>, which means eight asynchronous operations can execute
183	concurrently at any one time (the number of outstanding requests,	635	concurrently at any one time (the number of outstanding requests,
184	however, is unlimited).	636	however, is unlimited).
185		637
186	BDB starts threads only on demand, when an AIO request is queued and	638	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	639	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	640	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.	641	is in the cache and could have been processed faster by a single thread.
190		642
191	It is recommended to keep the number of threads relatively low, as some	643	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	648	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.	649	module selects a default that is suitable for low to moderate load.
198		650
199	=item BDB::max_parallel $nthreads	651	=item BDB::max_parallel $nthreads
200		652
201	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	653	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
202	specified number of threads are currently running, this function kills	654	specified number of threads are currently running, this function kills
203	them. This function blocks until the limit is reached.	655	them. This function blocks until the limit is reached.
204		656
205	While C<$nthreads> are zero, aio requests get queued but not executed	657	While C<$nthreads> are zero, aio requests get queued but not executed
206	until the number of threads has been increased again.	658	until the number of threads has been increased again.
…		…
245		697
246	=item BDB::set_sync_prepare $cb	698	=item BDB::set_sync_prepare $cb
247		699
248	Sets a callback that is called whenever a request is created without an	700	Sets a callback that is called whenever a request is created without an
249	explicit callback. It has to return two code references. The first is used	701	explicit callback. It has to return two code references. The first is used
250	as the request callback, and the second is called to wait until the first	702	as the request callback (it should save the return status), and the second
		703	is called to wait until the first callback has been called (it must set
		704	C<$!> to the return status).
		705
		706	This mechanism can be used to include BDB into other event mechanisms,
		707	such as L<AnyEvent::BDB> or L<Coro::BDB>.
		708
251	callback has been called. The default implementation works like this:	709	The default implementation works like this:
252		710
253	sub {	711	sub {
254	my $status;	712	my $status;
255	(	713	(
256	sub { $status = $! },	714	sub { $status = $! },
257	sub { BDB::poll while !defined $status; $! = $status },	715	sub { BDB::poll while !defined $status; $! = $status },
258	)	716	)
259	}	717	}
		718
		719	It simply blocks the process till the request has finished and then sets
		720	C<$!> to the return value. This means that if you don't use a callback,
		721	BDB will simply fall back to synchronous operations.
260		722
261	=back	723	=back
262		724
263	=head3 STATISTICAL INFORMATION	725	=head3 STATISTICAL INFORMATION
264		726
…		…
309		771
310	=head2 FORK BEHAVIOUR	772	=head2 FORK BEHAVIOUR
311		773
312	This module should do "the right thing" when the process using it forks:	774	This module should do "the right thing" when the process using it forks:
313		775
314	Before the fork, IO::AIO enters a quiescent state where no requests	776	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	777	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	778	the fork the parent simply leaves the quiescent state and continues
317	request/result processing, while the child frees the request/result queue	779	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	780	(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	781	parent). Threads will be started on demand until the limit set in the
320	parent process has been reached again.	782	parent process has been reached again.
321		783
322	In short: the parent will, after a short pause, continue as if fork had	784	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	785	not been called, while the child will act as if BDB has not been used
324	yet.	786	yet.
		787
		788	Win32 note: there is no fork on win32, and perls emulation of it is too
		789	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		790	yet, switch to a more capable platform.
325		791
326	=head2 MEMORY USAGE	792	=head2 MEMORY USAGE
327		793
328	Per-request usage:	794	Per-request usage:
329		795
…		…
331	bytes of memory. In addition, stat requests need a stat buffer (possibly	797	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	798	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	799	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.	800	will consume memory till the request has entered the done state.
335		801
336	This is now awfully much, so queuing lots of requests is not usually a	802	This is not awfully much, so queuing lots of requests is not usually a
337	problem.	803	problem.
338		804
339	Per-thread usage:	805	Per-thread usage:
340		806
341	In the execution phase, some aio requests require more memory for	807	In the execution phase, some aio requests require more memory for
342	temporary buffers, and each thread requires a stack and other data	808	temporary buffers, and each thread requires a stack and other data
343	structures (usually around 16k-128k, depending on the OS).	809	structures (usually around 16k-128k, depending on the OS).
344		810
345	=head1 KNOWN BUGS	811	=head1 KNOWN BUGS
346		812
347	Known bugs will be fixed in the next release.	813	Known bugs will be fixed in the next release, except:
		814
		815	If you use a transaction in any request, and the request returns
		816	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		817	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		818	above.
348		819
349	=head1 SEE ALSO	820	=head1 SEE ALSO
350		821
351	L<Coro::AIO>.	822	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		823	syntax), L<IO::AIO> (nice to have).
352		824
353	=head1 AUTHOR	825	=head1 AUTHOR
354		826
355	Marc Lehmann <schmorp@schmorp.de>	827	Marc Lehmann <schmorp@schmorp.de>
356	http://home.schmorp.de/	828	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 1.43 by root, Wed Jul 9 21:00:13 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 1.43 by root, Wed Jul 9 21:00:13 2008 UTC