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

Comparing BDB/BDB.pm (file contents):
Revision 1.9 by root, Sun Jul 8 14:57:59 2007 UTC vs.
Revision 1.40 by root, Tue Jul 8 08:35:12 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 = '0.5';	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	Example: set the log_autoremove option in a way compatible with <v.47 and
		552	v4.7. Note the use of & on the constants to avoid triggering a compiletime
		553	bug when the symbol isn't available.
		554
		555	$DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
		556	$DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
		557
		558	=over 4
		559
		560	=item BDB::VERSION
		561
		562	The C<BDB::VERSION> function, when called without arguments, returns the
		563	Berkeley DB version as a v-string (usually with 3 components). You should
		564	use C<lt> and C<ge> operators exclusively to make comparisons.
		565
		566	Example: check for at least version 4.7.
		567
		568	BDB::VERSION ge v4.7 or die;
		569
		570	=item BDB::VERSION min-version
		571
		572	Returns true if the BDB version is at least the given version (specified
		573	as a v-string), false otherwise.
		574
		575	Example: check for at least version 4.5.
		576
		577	BDB::VERSION v4.7 or die;
		578
		579	=item BDB::VERSION min-version, max-version
		580
		581	Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
		582	and less then C<max-version>.
		583
		584	Example: check wether version is strictly less then v4.7.
		585
		586	BDB::VERSION v0, v4.7
		587	or die "version 4.7 is not yet supported";
		588
		589	=back
		590
		591	=cut
		592
		593	sub VERSION {
		594	if (@_ > 0) {
		595	return undef if VERSION_v lt $_[0];
		596	if (@_ > 1) {
		597	return undef if VERSION_v ge $_[1];
		598	}
		599	}
		600
		601	VERSION_v
		602	}
		603
189	=head3 CONTROLLING THE NUMBER OF THREADS	604	=head3 CONTROLLING THE NUMBER OF THREADS
190		605
191	=over 4	606	=over 4
192		607
193	=item BDB::min_parallel $nthreads	608	=item BDB::min_parallel $nthreads
194		609
195	Set the minimum number of AIO threads to C<$nthreads>. The current	610	Set the minimum number of BDB threads to C<$nthreads>. The current
196	default is C<8>, which means eight asynchronous operations can execute	611	default is C<8>, which means eight asynchronous operations can execute
197	concurrently at any one time (the number of outstanding requests,	612	concurrently at any one time (the number of outstanding requests,
198	however, is unlimited).	613	however, is unlimited).
199		614
200	BDB starts threads only on demand, when an AIO request is queued and	615	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	616	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	617	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.	618	is in the cache and could have been processed faster by a single thread.
204		619
205	It is recommended to keep the number of threads relatively low, as some	620	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	625	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.	626	module selects a default that is suitable for low to moderate load.
212		627
213	=item BDB::max_parallel $nthreads	628	=item BDB::max_parallel $nthreads
214		629
215	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	630	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
216	specified number of threads are currently running, this function kills	631	specified number of threads are currently running, this function kills
217	them. This function blocks until the limit is reached.	632	them. This function blocks until the limit is reached.
218		633
219	While C<$nthreads> are zero, aio requests get queued but not executed	634	While C<$nthreads> are zero, aio requests get queued but not executed
220	until the number of threads has been increased again.	635	until the number of threads has been increased again.
…		…
259		674
260	=item BDB::set_sync_prepare $cb	675	=item BDB::set_sync_prepare $cb
261		676
262	Sets a callback that is called whenever a request is created without an	677	Sets a callback that is called whenever a request is created without an
263	explicit callback. It has to return two code references. The first is used	678	explicit callback. It has to return two code references. The first is used
264	as the request callback, and the second is called to wait until the first	679	as the request callback (it should save the return status), and the second
		680	is called to wait until the first callback has been called (it must set
		681	C<$!> to the return status).
		682
		683	This mechanism can be used to include BDB into other event mechanisms,
		684	such as L<AnyEvent::BDB> or L<Coro::BDB>.
		685
265	callback has been called. The default implementation works like this:	686	The default implementation works like this:
266		687
267	sub {	688	sub {
268	my $status;	689	my $status;
269	(	690	(
270	sub { $status = $! },	691	sub { $status = $! },
271	sub { BDB::poll while !defined $status; $! = $status },	692	sub { BDB::poll while !defined $status; $! = $status },
272	)	693	)
273	}	694	}
		695
		696	It simply blocks the process till the request has finished and then sets
		697	C<$!> to the return value. This means that if you don't use a callback,
		698	BDB will simply fall back to synchronous operations.
274		699
275	=back	700	=back
276		701
277	=head3 STATISTICAL INFORMATION	702	=head3 STATISTICAL INFORMATION
278		703
…		…
323		748
324	=head2 FORK BEHAVIOUR	749	=head2 FORK BEHAVIOUR
325		750
326	This module should do "the right thing" when the process using it forks:	751	This module should do "the right thing" when the process using it forks:
327		752
328	Before the fork, IO::AIO enters a quiescent state where no requests	753	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	754	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	755	the fork the parent simply leaves the quiescent state and continues
331	request/result processing, while the child frees the request/result queue	756	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	757	(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	758	parent). Threads will be started on demand until the limit set in the
334	parent process has been reached again.	759	parent process has been reached again.
335		760
336	In short: the parent will, after a short pause, continue as if fork had	761	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	762	not been called, while the child will act as if BDB has not been used
338	yet.	763	yet.
		764
		765	Win32 note: there is no fork on win32, and perls emulation of it is too
		766	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		767	yet, switch to a more capable platform.
339		768
340	=head2 MEMORY USAGE	769	=head2 MEMORY USAGE
341		770
342	Per-request usage:	771	Per-request usage:
343		772
…		…
345	bytes of memory. In addition, stat requests need a stat buffer (possibly	774	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	775	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	776	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.	777	will consume memory till the request has entered the done state.
349		778
350	This is now awfully much, so queuing lots of requests is not usually a	779	This is not awfully much, so queuing lots of requests is not usually a
351	problem.	780	problem.
352		781
353	Per-thread usage:	782	Per-thread usage:
354		783
355	In the execution phase, some aio requests require more memory for	784	In the execution phase, some aio requests require more memory for
356	temporary buffers, and each thread requires a stack and other data	785	temporary buffers, and each thread requires a stack and other data
357	structures (usually around 16k-128k, depending on the OS).	786	structures (usually around 16k-128k, depending on the OS).
358		787
359	=head1 KNOWN BUGS	788	=head1 KNOWN BUGS
360		789
361	Known bugs will be fixed in the next release.	790	Known bugs will be fixed in the next release, except:
		791
		792	If you use a transaction in any request, and the request returns
		793	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		794	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		795	above.
362		796
363	=head1 SEE ALSO	797	=head1 SEE ALSO
364		798
365	L<Coro::AIO>.	799	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		800	syntax), L<IO::AIO> (nice to have).
366		801
367	=head1 AUTHOR	802	=head1 AUTHOR
368		803
369	Marc Lehmann <schmorp@schmorp.de>	804	Marc Lehmann <schmorp@schmorp.de>
370	http://home.schmorp.de/	805	http://home.schmorp.de/

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Comparing BDB/BDB.pm (file contents): Revision 1.9 by root, Sun Jul 8 14:57:59 2007 UTC vs. Revision 1.40 by root, Tue Jul 8 08:35:12 2008 UTC

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Comparing BDB/BDB.pm (file contents):
Revision 1.9 by root, Sun Jul 8 14:57:59 2007 UTC vs.
Revision 1.40 by root, Tue Jul 8 08:35:12 2008 UTC