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

Comparing BDB/BDB.pm (file contents):
Revision 1.8 by root, Wed May 9 06:42:23 2007 UTC vs.
Revision 1.39 by root, Tue Jul 8 08:25:31 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	See the eg/ directory in the distribution and the berkeleydb C	48	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
12	documentation. This is inadequate, but the only sources of documentation	49	The BDB API is very similar to the C API (the translation has been very faithful).
13	known for this module so far.
14		50
15	=head2 EXAMPLE	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
16		58
17	=head1 REQUEST ANATOMY AND LIFETIME	59	=head1 REQUEST ANATOMY AND LIFETIME
18		60
19	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
20	directly visible to Perl.	62	directly visible to Perl.
…		…
67	use strict 'vars';	109	use strict 'vars';
68		110
69	use base 'Exporter';	111	use base 'Exporter';
70		112
71	BEGIN {	113	BEGIN {
72	our $VERSION = '0.1';	114	our $VERSION = '1.6';
73		115
74	our @BDB_REQ = qw(	116	our @BDB_REQ = qw(
75	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect	117	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
76	db_env_memp_sync db_env_memp_trickle	118	db_env_memp_sync db_env_memp_trickle db_env_dbrename db_env_dbremove
77	db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range	119	db_open db_close db_compact db_sync db_upgrade
		120	db_put db_get db_pget db_del db_key_range
78	db_txn_commit db_txn_abort	121	db_txn_commit db_txn_abort db_txn_finish
79	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del	122	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
80	db_sequence_open db_sequence_close	123	db_sequence_open db_sequence_close
81	db_sequence_get db_sequence_remove	124	db_sequence_get db_sequence_remove
82	);	125	);
83	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));	126	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
…		…
90		133
91	require XSLoader;	134	require XSLoader;
92	XSLoader::load ("BDB", $VERSION);	135	XSLoader::load ("BDB", $VERSION);
93	}	136	}
94		137
		138	=head2 WIN32 FILENAMES/DATABASE NAME MESS
		139
		140	Perl on Win32 supports only ASCII filenames (the reason is that it abuses
		141	an internal flag to store wether a filename is Unicode or ANSI, but that
		142	flag is used for somethign else in the perl core, so there is no way to
		143	detect wether a filename is ANSI or Unicode-encoded). The BDB module
		144	tries to work around this issue by assuming that the filename is an ANSI
		145	filename and BDB was built for unicode support.
		146
		147	=head2 BERKELEYDB FUNCTIONS
		148
		149	All of these are functions. The create functions simply return a new
		150	object and never block. All the remaining functions take an optional
		151	callback as last argument. If it is missing, then the function will be
		152	executed synchronously. In both cases, C<$!> 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	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, bdb_filename 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	db_env_dbremove (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
		191	db_env_dbrename (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = &PL_sv_undef)
		192
		193	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		194	flags: XA_CREATE
		195
		196	db_open (DB db, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		197	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		198	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		199	flags: DB_NOSYNC
		200	db_upgrade (DB db, bdb_filename file, U32 flags = 0, SV callback = &PL_sv_undef)
		201	db_compact (DB db, DB_TXN_ornull txn = 0, SV start = 0, SV stop = 0, SV unused1 = 0, U32 flags = DB_FREE_SPACE, SV unused2 = 0, SV *callback = &PL_sv_undef)
		202	flags: FREELIST_ONLY FREE_SPACE
		203	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		204	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		205	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		206	flags: APPEND NODUPDATA NOOVERWRITE
		207	db_get (DB db, DB_TXN_ornull txn, SV key, 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_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		210	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		211	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		212	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		213	flags: TXN_NOSYNC TXN_SYNC
		214	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		215
		216	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		217	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		218	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		219	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		220	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		221	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
		222	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		223	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		224
		225	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		226	flags: CREATE EXCL
		227	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		228	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)
		229	flags: TXN_NOSYNC
		230	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		231	flags: TXN_NOSYNC
		232
		233	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		234
		235	This is not actually a Berkeley DB function but a BDB module
		236	extension. The background for this exytension is: It is very annoying to
		237	have to check every single BDB function for error returns and provide a
		238	codepath out of your transaction. While the BDB module still makes this
		239	possible, it contains the following extensions:
		240
		241	When a transaction-protected function returns any operating system
		242	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		243	transaction. This flag is also set by Berkeley DB functions themselves
		244	when an operation fails with LOCK_DEADLOCK, and it causes all further
		245	operations on that transaction (including C<db_txn_commit>) to fail.
		246
		247	The C<db_txn_finish> request will look at this flag, and, if it is set,
		248	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		249	if it isn't set to something else yet). If it isn't set, it will call
		250	C<db_txn_commit> and return the error normally.
		251
		252	How to use this? Easy: just write your transaction normally:
		253
		254	my $txn = $db_env->txn_begin;
		255	db_get $db, $txn, "key", my $data;
		256	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		257	db_txn_finish $txn;
		258	die "transaction failed" if $!;
		259
		260	That is, handle only the expected errors. If something unexpected happens
		261	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		262	requests (db_put in this case) will simply be skipped (they will fail with
		263	LOCK_DEADLOCK) and the transaction will be aborted.
		264
		265	You can use the C<< $txn->failed >> method to check wether a transaction
		266	has failed in this way and abort further processing (excluding
		267	C<db_txn_finish>).
		268
		269	=head3 DB_ENV/database environment methods
		270
		271	Methods available on DB_ENV/$env handles:
		272
		273	DESTROY (DB_ENV_ornull *env)
		274	CODE:
		275	if (env)
		276	env->close (env, 0);
		277
		278	$int = $env->set_data_dir (const char *dir)
		279	$int = $env->set_tmp_dir (const char *dir)
		280	$int = $env->set_lg_dir (const char *dir)
		281	$int = $env->set_shm_key (long shm_key)
		282	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		283	$int = $env->set_flags (U32 flags, int onoff = 1)
		284	$int = $env->log_set_config (U32 flags, int onoff = 1) [v4.7]
		285	$int = $env->set_intermediate_dir_mode (const char *modestring) [v4.7]
		286	$env->set_errfile (FILE *errfile = 0)
		287	$env->set_msgfile (FILE *msgfile = 0)
		288	$int = $env->set_verbose (U32 which, int onoff = 1)
		289	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		290	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		291	$int = $env->set_mp_max_openfd (int maxopenfd);
		292	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		293	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		294	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		295	$int = $env->set_lk_max_lockers (U32 max)
		296	$int = $env->set_lk_max_locks (U32 max)
		297	$int = $env->set_lk_max_objects (U32 max)
		298	$int = $env->set_lg_bsize (U32 max)
		299	$int = $env->set_lg_max (U32 max)
		300	$int = $env->mutex_set_increment (U32 increment)
		301	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		302	$int = $env->mutex_set_max (U32 max)
		303	$int = $env->mutex_set_align (U32 align)
		304
		305	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		306	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		307
		308	=head4 Example:
		309
		310	use AnyEvent;
		311	use BDB;
		312
		313	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		314	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		315
		316	BDB::min_parallel 8;
		317
		318	my $env = db_env_create;
		319
		320	mkdir "bdtest", 0700;
		321	db_env_open
		322	$env,
		323	"bdtest",
		324	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		325	0600;
		326
		327	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		328
		329
		330	=head3 DB/database methods
		331
		332	Methods available on DB/$db handles:
		333
		334	DESTROY (DB_ornull *db)
		335	CODE:
		336	if (db)
		337	{
		338	SV env = (SV )db->app_private;
		339	db->close (db, 0);
		340	SvREFCNT_dec (env);
		341	}
		342
		343	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		344	$int = $db->set_flags (U32 flags)
		345	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		346	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		347	Hash: DUP DUPSORT
		348	Queue: INORDER
		349	Recno: RENUMBER SNAPSHOT
		350
		351	$int = $db->set_encrypt (const char *password, U32 flags)
		352	$int = $db->set_lorder (int lorder)
		353	$int = $db->set_bt_minkey (U32 minkey)
		354	$int = $db->set_re_delim (int delim)
		355	$int = $db->set_re_pad (int re_pad)
		356	$int = $db->set_re_source (char *source)
		357	$int = $db->set_re_len (U32 re_len)
		358	$int = $db->set_h_ffactor (U32 h_ffactor)
		359	$int = $db->set_h_nelem (U32 h_nelem)
		360	$int = $db->set_q_extentsize (U32 extentsize)
		361
		362	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		363	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		364	$seq = $db->sequence (U32 flags = 0)
		365
		366	=head4 Example:
		367
		368	my $db = db_create $env;
		369	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		370
		371	for (1..1000) {
		372	db_put $db, undef, "key $_", "data $_";
		373
		374	db_key_range $db, undef, "key $_", my $keyrange;
		375	my ($lt, $eq, $gt) = @$keyrange;
		376	}
		377
		378	db_del $db, undef, "key $_" for 1..1000;
		379
		380	db_sync $db;
		381
		382
		383	=head3 DB_TXN/transaction methods
		384
		385	Methods available on DB_TXN/$txn handles:
		386
		387	DESTROY (DB_TXN_ornull *txn)
		388	CODE:
		389	if (txn)
		390	txn->abort (txn);
		391
		392	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		393	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		394
		395	$bool = $txn->failed
		396	# see db_txn_finish documentation, above
		397
		398
		399	=head3 DBC/cursor methods
		400
		401	Methods available on DBC/$dbc handles:
		402
		403	DESTROY (DBC_ornull *dbc)
		404	CODE:
		405	if (dbc)
		406	dbc->c_close (dbc);
		407
		408	$int = $cursor->set_priority ($priority = PRIORITY_*)
		409
		410	=head4 Example:
		411
		412	my $c = $db->cursor;
		413
		414	for (;;) {
		415	db_c_get $c, my $key, my $data, BDB::NEXT;
		416	warn "<$!,$key,$data>";
		417	last if $!;
		418	}
		419
		420	db_c_close $c;
		421
		422
		423	=head3 DB_SEQUENCE/sequence methods
		424
		425	Methods available on DB_SEQUENCE/$seq handles:
		426
		427	DESTROY (DB_SEQUENCE_ornull *seq)
		428	CODE:
		429	if (seq)
		430	seq->close (seq, 0);
		431
		432	$int = $seq->initial_value (db_seq_t value)
		433	$int = $seq->set_cachesize (U32 size)
		434	$int = $seq->set_flags (U32 flags)
		435	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		436	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		437
		438	=head4 Example:
		439
		440	my $seq = $db->sequence;
		441
		442	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		443	db_sequence_get $seq, undef, 1, my $value;
		444
		445
95	=head2 SUPPORT FUNCTIONS	446	=head2 SUPPORT FUNCTIONS
96		447
97	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	448	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
98		449
99	=over 4	450	=over 4
		451
		452	=item $msg = BDB::strerror [$errno]
		453
		454	Returns the string corresponding to the given errno value. If no argument
		455	is given, use C<$!>.
		456
		457	Note that the BDB module also patches the C<$!> variable directly, so you
		458	should be able to get a bdb error string by simply stringifying C<$!>.
100		459
101	=item $fileno = BDB::poll_fileno	460	=item $fileno = BDB::poll_fileno
102		461
103	Return the I<request result pipe file descriptor>. This filehandle must be	462	Return the I<request result pipe file descriptor>. This filehandle must be
104	polled for reading by some mechanism outside this module (e.g. Event or	463	polled for reading by some mechanism outside this module (e.g. Event or
…		…
143	interactiveness when perl is not fast enough to process all requests in	502	interactiveness when perl is not fast enough to process all requests in
144	time.	503	time.
145		504
146	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	505	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
147		506
148	Example: Install an Event watcher that automatically calls	507	Example: Install an EV watcher that automatically calls
149	BDB::poll_cb with low priority, to ensure that other parts of the	508	BDB::poll_cb with low priority, to ensure that other parts of the
150	program get the CPU sometimes even under high AIO load.	509	program get the CPU sometimes even under high load.
151		510
152	# try not to spend much more than 0.1s in poll_cb	511	# try not to spend much more than 0.1s in poll_cb
153	BDB::max_poll_time 0.1;	512	BDB::max_poll_time 0.1;
154		513
155	# use a low priority so other tasks have priority	514	my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
156	Event->io (fd => BDB::poll_fileno,
157	poll => 'r', nice => 1,
158	cb => &BDB::poll_cb);
159		515
160	=item BDB::poll_wait	516	=item BDB::poll_wait
161		517
162	If there are any outstanding requests and none of them in the result	518	If there are any outstanding requests and none of them in the result
163	phase, wait till the result filehandle becomes ready for reading (simply	519	phase, wait till the result filehandle becomes ready for reading (simply
…		…
175		531
176	BDB::poll_wait, BDB::poll_cb	532	BDB::poll_wait, BDB::poll_cb
177		533
178	=item BDB::flush	534	=item BDB::flush
179		535
180	Wait till all outstanding AIO requests have been handled.	536	Wait till all outstanding BDB requests have been handled.
181		537
182	Strictly equivalent to:	538	Strictly equivalent to:
183		539
184	BDB::poll_wait, BDB::poll_cb	540	BDB::poll_wait, BDB::poll_cb
185	while BDB::nreqs;	541	while BDB::nreqs;
186		542
187	=back	543	=back
188		544
		545	=head3 VERSION CHECKING
		546
		547	BerkeleyDB comes in various versions, many of them have minor
		548	incompatibilities. This means that traditional "at least version x.x"
		549	checks are often not sufficient.
		550
		551	=over 4
		552
		553	=item BDB::VERSION
		554
		555	The C<BDB::VERSION> function, when called without arguments, returns the
		556	Berkeley DB version as a v-string (usually with 3 components). You should
		557	use C<lt> and C<ge> operators exclusively to make comparisons.
		558
		559	Example: check for at least version 4.7.
		560
		561	BDB::VERSION ge v4.7 or die;
		562
		563	=item BDB::VERSION min-version
		564
		565	Returns true if the BDB version is at least the given version (specified
		566	as a v-string), false otherwise.
		567
		568	Example: check for at least version 4.5.
		569
		570	BDB::VERSION v4.7 or die;
		571
		572	=item BDB::VERSION min-version, max-version
		573
		574	Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
		575	and less then C<max-version>.
		576
		577	Example: check wether version is strictly less then v4.7.
		578
		579	BDB::VERSION v0, v4.7
		580	or die "version 4.7 is not yet supported";
		581
		582	=back
		583
		584	=cut
		585
		586	sub VERSION {
		587	if (@_ > 0) {
		588	return undef if VERSION_v lt $_[0];
		589	if (@_ > 1) {
		590	return undef if VERSION_v ge $_[1];
		591	}
		592	}
		593
		594	VERSION_v
		595	}
		596
189	=head3 CONTROLLING THE NUMBER OF THREADS	597	=head3 CONTROLLING THE NUMBER OF THREADS
190		598
191	=over 4	599	=over 4
192		600
193	=item BDB::min_parallel $nthreads	601	=item BDB::min_parallel $nthreads
194		602
195	Set the minimum number of AIO threads to C<$nthreads>. The current	603	Set the minimum number of BDB threads to C<$nthreads>. The current
196	default is C<8>, which means eight asynchronous operations can execute	604	default is C<8>, which means eight asynchronous operations can execute
197	concurrently at any one time (the number of outstanding requests,	605	concurrently at any one time (the number of outstanding requests,
198	however, is unlimited).	606	however, is unlimited).
199		607
200	BDB starts threads only on demand, when an AIO request is queued and	608	BDB starts threads only on demand, when an BDB request is queued and
201	no free thread exists. Please note that queueing up a hundred requests can	609	no free thread exists. Please note that queueing up a hundred requests can
202	create demand for a hundred threads, even if it turns out that everything	610	create demand for a hundred threads, even if it turns out that everything
203	is in the cache and could have been processed faster by a single thread.	611	is in the cache and could have been processed faster by a single thread.
204		612
205	It is recommended to keep the number of threads relatively low, as some	613	It is recommended to keep the number of threads relatively low, as some
…		…
210	Under most circumstances you don't need to call this function, as the	618	Under most circumstances you don't need to call this function, as the
211	module selects a default that is suitable for low to moderate load.	619	module selects a default that is suitable for low to moderate load.
212		620
213	=item BDB::max_parallel $nthreads	621	=item BDB::max_parallel $nthreads
214		622
215	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	623	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
216	specified number of threads are currently running, this function kills	624	specified number of threads are currently running, this function kills
217	them. This function blocks until the limit is reached.	625	them. This function blocks until the limit is reached.
218		626
219	While C<$nthreads> are zero, aio requests get queued but not executed	627	While C<$nthreads> are zero, aio requests get queued but not executed
220	until the number of threads has been increased again.	628	until the number of threads has been increased again.
…		…
259		667
260	=item BDB::set_sync_prepare $cb	668	=item BDB::set_sync_prepare $cb
261		669
262	Sets a callback that is called whenever a request is created without an	670	Sets a callback that is called whenever a request is created without an
263	explicit callback. It has to return two code references. The first is used	671	explicit callback. It has to return two code references. The first is used
264	as the request callback, and the second is called to wait until the first	672	as the request callback (it should save the return status), and the second
		673	is called to wait until the first callback has been called (it must set
		674	C<$!> to the return status).
		675
		676	This mechanism can be used to include BDB into other event mechanisms,
		677	such as L<AnyEvent::BDB> or L<Coro::BDB>.
		678
265	callback has been called. The default implementation works like this:	679	The default implementation works like this:
266		680
267	sub {	681	sub {
268	my $status;	682	my $status;
269	(	683	(
270	sub { $status = $! },	684	sub { $status = $! },
271	sub { BDB::poll while !defined $status; $! = $status },	685	sub { BDB::poll while !defined $status; $! = $status },
272	)	686	)
273	}	687	}
		688
		689	It simply blocks the process till the request has finished and then sets
		690	C<$!> to the return value. This means that if you don't use a callback,
		691	BDB will simply fall back to synchronous operations.
274		692
275	=back	693	=back
276		694
277	=head3 STATISTICAL INFORMATION	695	=head3 STATISTICAL INFORMATION
278		696
…		…
323		741
324	=head2 FORK BEHAVIOUR	742	=head2 FORK BEHAVIOUR
325		743
326	This module should do "the right thing" when the process using it forks:	744	This module should do "the right thing" when the process using it forks:
327		745
328	Before the fork, IO::AIO enters a quiescent state where no requests	746	Before the fork, BDB enters a quiescent state where no requests
329	can be added in other threads and no results will be processed. After	747	can be added in other threads and no results will be processed. After
330	the fork the parent simply leaves the quiescent state and continues	748	the fork the parent simply leaves the quiescent state and continues
331	request/result processing, while the child frees the request/result queue	749	request/result processing, while the child frees the request/result queue
332	(so that the requests started before the fork will only be handled in the	750	(so that the requests started before the fork will only be handled in the
333	parent). Threads will be started on demand until the limit set in the	751	parent). Threads will be started on demand until the limit set in the
334	parent process has been reached again.	752	parent process has been reached again.
335		753
336	In short: the parent will, after a short pause, continue as if fork had	754	In short: the parent will, after a short pause, continue as if fork had
337	not been called, while the child will act as if IO::AIO has not been used	755	not been called, while the child will act as if BDB has not been used
338	yet.	756	yet.
		757
		758	Win32 note: there is no fork on win32, and perls emulation of it is too
		759	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		760	yet, switch to a more capable platform.
339		761
340	=head2 MEMORY USAGE	762	=head2 MEMORY USAGE
341		763
342	Per-request usage:	764	Per-request usage:
343		765
…		…
345	bytes of memory. In addition, stat requests need a stat buffer (possibly	767	bytes of memory. In addition, stat requests need a stat buffer (possibly
346	a few hundred bytes), readdir requires a result buffer and so on. Perl	768	a few hundred bytes), readdir requires a result buffer and so on. Perl
347	scalars and other data passed into aio requests will also be locked and	769	scalars and other data passed into aio requests will also be locked and
348	will consume memory till the request has entered the done state.	770	will consume memory till the request has entered the done state.
349		771
350	This is now awfully much, so queuing lots of requests is not usually a	772	This is not awfully much, so queuing lots of requests is not usually a
351	problem.	773	problem.
352		774
353	Per-thread usage:	775	Per-thread usage:
354		776
355	In the execution phase, some aio requests require more memory for	777	In the execution phase, some aio requests require more memory for
356	temporary buffers, and each thread requires a stack and other data	778	temporary buffers, and each thread requires a stack and other data
357	structures (usually around 16k-128k, depending on the OS).	779	structures (usually around 16k-128k, depending on the OS).
358		780
359	=head1 KNOWN BUGS	781	=head1 KNOWN BUGS
360		782
361	Known bugs will be fixed in the next release.	783	Known bugs will be fixed in the next release, except:
		784
		785	If you use a transaction in any request, and the request returns
		786	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		787	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		788	above.
362		789
363	=head1 SEE ALSO	790	=head1 SEE ALSO
364		791
365	L<Coro::AIO>.	792	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		793	syntax), L<IO::AIO> (nice to have).
366		794
367	=head1 AUTHOR	795	=head1 AUTHOR
368		796
369	Marc Lehmann <schmorp@schmorp.de>	797	Marc Lehmann <schmorp@schmorp.de>
370	http://home.schmorp.de/	798	http://home.schmorp.de/

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Comparing BDB/BDB.pm (file contents): Revision 1.8 by root, Wed May 9 06:42:23 2007 UTC vs. Revision 1.39 by root, Tue Jul 8 08:25:31 2008 UTC

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Comparing BDB/BDB.pm (file contents):
Revision 1.8 by root, Wed May 9 06:42:23 2007 UTC vs.
Revision 1.39 by root, Tue Jul 8 08:25:31 2008 UTC