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

Comparing BDB/BDB.pm (file contents):
Revision 1.2 by root, Mon Feb 5 20:21:38 2007 UTC vs.
Revision 1.48 by root, Tue Jul 29 03:33:16 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.
…		…
62	no warnings;	108	no warnings;
63	use strict 'vars';	109	use strict 'vars';
64		110
65	use base 'Exporter';	111	use base 'Exporter';
66		112
		113	our $VERSION;
		114
67	BEGIN {	115	BEGIN {
68	our $VERSION = '0.1';	116	$VERSION = '1.71';
69		117
70	our @BDB_REQ = qw();	118	our @BDB_REQ = qw(
		119	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		120	db_env_memp_sync db_env_memp_trickle db_env_dbrename db_env_dbremove
		121	db_open db_close db_compact db_sync db_upgrade
		122	db_put db_exists db_get db_pget db_del db_key_range
		123	db_txn_commit db_txn_abort db_txn_finish
		124	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		125	db_sequence_open db_sequence_close
		126	db_sequence_get db_sequence_remove
		127	);
		128	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		129	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	130	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	131	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	132	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	133	max_poll_time max_poll_reqs
		134	);
75		135
76	require XSLoader;	136	require XSLoader;
77	XSLoader::load ("BDB", $VERSION);	137	XSLoader::load ("BDB", $VERSION);
78	}	138	}
79		139
		140	=head2 WIN32 FILENAMES/DATABASE NAME MESS
		141
		142	Perl on Win32 supports only ASCII filenames (the reason is that it abuses
		143	an internal flag to store wether a filename is Unicode or ANSI, but that
		144	flag is used for somethign else in the perl core, so there is no way to
		145	detect wether a filename is ANSI or Unicode-encoded). The BDB module
		146	tries to work around this issue by assuming that the filename is an ANSI
		147	filename and BDB was built for unicode support.
		148
		149	=head2 BERKELEYDB FUNCTIONS
		150
		151	All of these are functions. The create functions simply return a new
		152	object and never block. All the remaining functions take an optional
		153	callback as last argument. If it is missing, then the function will be
		154	executed synchronously. In both cases, C<$!> will reflect the return value
		155	of the function.
		156
		157	BDB functions that cannot block (mostly functions that manipulate
		158	settings) are method calls on the relevant objects, so the rule of thumb
		159	is: if it's a method, it's not blocking, if it's a function, it takes a
		160	callback as last argument.
		161
		162	In the following, C<$int> signifies an integer return value,
		163	C<bdb_filename> is a "filename" (octets on unix, madness on windows),
		164	C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
		165	floating point value.
		166
		167	Most C<SV *> types are generic perl scalars (for input and output of data
		168	values).
		169
		170	The various C<DB_ENV> etc. arguments are handles return by
		171	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		172	appended C<_ornull> this means they are optional and you can pass C<undef>
		173	for them, resulting a NULL pointer on the C level.
		174
		175	The C<SV *callback> is the optional callback function to call when the
		176	request is completed. This last callback argument is special: the callback
		177	is simply the last argument passed. If there are "optional" arguments
		178	before the callback they can be left out. The callback itself can be left
		179	out or specified as C<undef>, in which case the function will be executed
		180	synchronously.
		181
		182	For example, C<db_env_txn_checkpoint> usually is called with all integer
		183	arguments zero. These can be left out, so all of these specify a call
		184	to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
		185	callback to be called:
		186
		187	db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
		188	db_env_txn_checkpoint $db_env, 0, 0, sub { };
		189	db_env_txn_checkpoint $db_env, sub { };
		190
		191	While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
		192	executed synchronously:
		193
		194	db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
		195	db_env_txn_checkpoint $db_env, 0, 0, 0;
		196	db_env_txn_checkpoint $db_env, 0;
		197
		198	=head3 BDB functions
		199
		200	Functions in the BDB namespace, exported by default:
		201
		202	$env = db_env_create (U32 env_flags = 0)
		203	flags: RPCCLIENT
		204
		205	db_env_open (DB_ENV env, bdb_filename db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		206	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
		207	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		208	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		209	flags: FORCE
		210	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		211	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		212	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		213	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		214	db_env_dbremove (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
		215	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)
		216
		217	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		218	flags: XA_CREATE
		219
		220	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)
		221	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		222	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		223	flags: DB_NOSYNC
		224	db_upgrade (DB db, bdb_filename file, U32 flags = 0, SV callback = &PL_sv_undef)
		225	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)
		226	flags: FREELIST_ONLY FREE_SPACE
		227	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		228	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		229	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		230	flags: APPEND NODUPDATA NOOVERWRITE
		231	db_exists (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = 0) (v4.6)
		232	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		233	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		234	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		235	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		236	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		237	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		238	flags: TXN_NOSYNC TXN_SYNC
		239	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		240
		241	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		242	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		243	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		244	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		245	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		246	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
		247	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		248	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		249
		250	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		251	flags: CREATE EXCL
		252	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		253	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)
		254	flags: TXN_NOSYNC
		255	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		256	flags: TXN_NOSYNC
		257
		258	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		259
		260	This is not actually a Berkeley DB function but a BDB module
		261	extension. The background for this exytension is: It is very annoying to
		262	have to check every single BDB function for error returns and provide a
		263	codepath out of your transaction. While the BDB module still makes this
		264	possible, it contains the following extensions:
		265
		266	When a transaction-protected function returns any operating system
		267	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		268	transaction. This flag is also set by Berkeley DB functions themselves
		269	when an operation fails with LOCK_DEADLOCK, and it causes all further
		270	operations on that transaction (including C<db_txn_commit>) to fail.
		271
		272	The C<db_txn_finish> request will look at this flag, and, if it is set,
		273	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		274	if it isn't set to something else yet). If it isn't set, it will call
		275	C<db_txn_commit> and return the error normally.
		276
		277	How to use this? Easy: just write your transaction normally:
		278
		279	my $txn = $db_env->txn_begin;
		280	db_get $db, $txn, "key", my $data;
		281	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		282	db_txn_finish $txn;
		283	die "transaction failed" if $!;
		284
		285	That is, handle only the expected errors. If something unexpected happens
		286	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		287	requests (db_put in this case) will simply be skipped (they will fail with
		288	LOCK_DEADLOCK) and the transaction will be aborted.
		289
		290	You can use the C<< $txn->failed >> method to check wether a transaction
		291	has failed in this way and abort further processing (excluding
		292	C<db_txn_finish>).
		293
		294	=head3 DB_ENV/database environment methods
		295
		296	Methods available on DB_ENV/$env handles:
		297
		298	DESTROY (DB_ENV_ornull *env)
		299	CODE:
		300	if (env)
		301	env->close (env, 0);
		302
		303	$int = $env->set_data_dir (const char *dir)
		304	$int = $env->set_tmp_dir (const char *dir)
		305	$int = $env->set_lg_dir (const char *dir)
		306	$int = $env->set_shm_key (long shm_key)
		307	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		308	$int = $env->set_flags (U32 flags, int onoff = 1)
		309	$int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
		310	$int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
		311	$env->set_errfile (FILE *errfile = 0)
		312	$env->set_msgfile (FILE *msgfile = 0)
		313	$int = $env->set_verbose (U32 which, int onoff = 1)
		314	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		315	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		316	$int = $env->set_mp_max_openfd (int maxopenfd);
		317	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		318	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		319	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		320	$int = $env->set_lk_max_lockers (U32 max)
		321	$int = $env->set_lk_max_locks (U32 max)
		322	$int = $env->set_lk_max_objects (U32 max)
		323	$int = $env->set_lg_bsize (U32 max)
		324	$int = $env->set_lg_max (U32 max)
		325	$int = $env->mutex_set_increment (U32 increment)
		326	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		327	$int = $env->mutex_set_max (U32 max)
		328	$int = $env->mutex_set_align (U32 align)
		329
		330	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		331	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		332	$txn = $env->cdsgroup_begin; (v4.5)
		333
		334	=head4 Example:
		335
		336	use AnyEvent;
		337	use BDB;
		338
		339	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		340	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		341
		342	BDB::min_parallel 8;
		343
		344	my $env = db_env_create;
		345
		346	mkdir "bdtest", 0700;
		347	db_env_open
		348	$env,
		349	"bdtest",
		350	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		351	0600;
		352
		353	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		354
		355
		356	=head3 DB/database methods
		357
		358	Methods available on DB/$db handles:
		359
		360	DESTROY (DB_ornull *db)
		361	CODE:
		362	if (db)
		363	{
		364	SV env = (SV )db->app_private;
		365	db->close (db, 0);
		366	SvREFCNT_dec (env);
		367	}
		368
		369	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		370	$int = $db->set_flags (U32 flags)
		371	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		372	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		373	Hash: DUP DUPSORT
		374	Queue: INORDER
		375	Recno: RENUMBER SNAPSHOT
		376
		377	$int = $db->set_encrypt (const char *password, U32 flags)
		378	$int = $db->set_lorder (int lorder)
		379	$int = $db->set_bt_minkey (U32 minkey)
		380	$int = $db->set_re_delim (int delim)
		381	$int = $db->set_re_pad (int re_pad)
		382	$int = $db->set_re_source (char *source)
		383	$int = $db->set_re_len (U32 re_len)
		384	$int = $db->set_h_ffactor (U32 h_ffactor)
		385	$int = $db->set_h_nelem (U32 h_nelem)
		386	$int = $db->set_q_extentsize (U32 extentsize)
		387
		388	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		389	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		390	$seq = $db->sequence (U32 flags = 0)
		391
		392	=head4 Example:
		393
		394	my $db = db_create $env;
		395	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		396
		397	for (1..1000) {
		398	db_put $db, undef, "key $_", "data $_";
		399
		400	db_key_range $db, undef, "key $_", my $keyrange;
		401	my ($lt, $eq, $gt) = @$keyrange;
		402	}
		403
		404	db_del $db, undef, "key $_" for 1..1000;
		405
		406	db_sync $db;
		407
		408
		409	=head3 DB_TXN/transaction methods
		410
		411	Methods available on DB_TXN/$txn handles:
		412
		413	DESTROY (DB_TXN_ornull *txn)
		414	CODE:
		415	if (txn)
		416	txn->abort (txn);
		417
		418	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		419	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		420
		421	$bool = $txn->failed
		422	# see db_txn_finish documentation, above
		423
		424
		425	=head3 DBC/cursor methods
		426
		427	Methods available on DBC/$dbc handles:
		428
		429	DESTROY (DBC_ornull *dbc)
		430	CODE:
		431	if (dbc)
		432	dbc->c_close (dbc);
		433
		434	$int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
		435
		436	=head4 Example:
		437
		438	my $c = $db->cursor;
		439
		440	for (;;) {
		441	db_c_get $c, my $key, my $data, BDB::NEXT;
		442	warn "<$!,$key,$data>";
		443	last if $!;
		444	}
		445
		446	db_c_close $c;
		447
		448
		449	=head3 DB_SEQUENCE/sequence methods
		450
		451	Methods available on DB_SEQUENCE/$seq handles:
		452
		453	DESTROY (DB_SEQUENCE_ornull *seq)
		454	CODE:
		455	if (seq)
		456	seq->close (seq, 0);
		457
		458	$int = $seq->initial_value (db_seq_t value)
		459	$int = $seq->set_cachesize (U32 size)
		460	$int = $seq->set_flags (U32 flags)
		461	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		462	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		463
		464	=head4 Example:
		465
		466	my $seq = $db->sequence;
		467
		468	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		469	db_sequence_get $seq, undef, 1, my $value;
		470
		471
80	=head2 SUPPORT FUNCTIONS	472	=head2 SUPPORT FUNCTIONS
81		473
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	474	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		475
84	=over 4	476	=over 4
		477
		478	=item $msg = BDB::strerror [$errno]
		479
		480	Returns the string corresponding to the given errno value. If no argument
		481	is given, use C<$!>.
		482
		483	Note that the BDB module also patches the C<$!> variable directly, so you
		484	should be able to get a bdb error string by simply stringifying C<$!>.
85		485
86	=item $fileno = BDB::poll_fileno	486	=item $fileno = BDB::poll_fileno
87		487
88	Return the I<request result pipe file descriptor>. This filehandle must be	488	Return the I<request result pipe file descriptor>. This filehandle must be
89	polled for reading by some mechanism outside this module (e.g. Event or	489	polled for reading by some mechanism outside this module (e.g. Event or
…		…
128	interactiveness when perl is not fast enough to process all requests in	528	interactiveness when perl is not fast enough to process all requests in
129	time.	529	time.
130		530
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	531	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		532
133	Example: Install an Event watcher that automatically calls	533	Example: Install an EV watcher that automatically calls
134	BDB::poll_cb with low priority, to ensure that other parts of the	534	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	535	program get the CPU sometimes even under high load.
136		536
137	# try not to spend much more than 0.1s in poll_cb	537	# try not to spend much more than 0.1s in poll_cb
138	BDB::max_poll_time 0.1;	538	BDB::max_poll_time 0.1;
139		539
140	# use a low priority so other tasks have priority	540	my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
141	Event->io (fd => BDB::poll_fileno,
142	poll => 'r', nice => 1,
143	cb => &BDB::poll_cb);
144		541
145	=item BDB::poll_wait	542	=item BDB::poll_wait
146		543
147	If there are any outstanding requests and none of them in the result	544	If there are any outstanding requests and none of them in the result
148	phase, wait till the result filehandle becomes ready for reading (simply	545	phase, wait till the result filehandle becomes ready for reading (simply
…		…
160		557
161	BDB::poll_wait, BDB::poll_cb	558	BDB::poll_wait, BDB::poll_cb
162		559
163	=item BDB::flush	560	=item BDB::flush
164		561
165	Wait till all outstanding AIO requests have been handled.	562	Wait till all outstanding BDB requests have been handled.
166		563
167	Strictly equivalent to:	564	Strictly equivalent to:
168		565
169	BDB::poll_wait, BDB::poll_cb	566	BDB::poll_wait, BDB::poll_cb
170	while BDB::nreqs;	567	while BDB::nreqs;
171		568
		569	=back
		570
		571	=head3 VERSION CHECKING
		572
		573	BerkeleyDB comes in various versions, many of them have minor
		574	incompatibilities. This means that traditional "at least version x.x"
		575	checks are often not sufficient.
		576
		577	Example: set the log_autoremove option in a way compatible with <v4.7 and
		578	v4.7. Note the use of & on the constants to avoid triggering a compiletime
		579	bug when the symbol isn't available.
		580
		581	$DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
		582	$DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
		583
		584	=over 4
		585
		586	=item BDB::VERSION
		587
		588	The C<BDB::VERSION> function, when called without arguments, returns the
		589	Berkeley DB version as a v-string (usually with 3 components). You should
		590	use C<lt> and C<ge> operators exclusively to make comparisons.
		591
		592	Example: check for at least version 4.7.
		593
		594	BDB::VERSION ge v4.7 or die;
		595
		596	=item BDB::VERSION min-version
		597
		598	Returns true if the BDB version is at least the given version (specified
		599	as a v-string), false otherwise.
		600
		601	Example: check for at least version 4.5.
		602
		603	BDB::VERSION v4.7 or die;
		604
		605	=item BDB::VERSION min-version, max-version
		606
		607	Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
		608	and less then C<max-version>.
		609
		610	Example: check wether version is strictly less then v4.7.
		611
		612	BDB::VERSION v0, v4.7
		613	or die "version 4.7 is not yet supported";
		614
		615	=back
		616
		617	=cut
		618
		619	sub VERSION {
		620	# I was dumb enough to override the VERSION method here, so let's try
		621	# to fix it up.
		622
		623	if ($_[0] eq __PACKAGE__) {
		624	$VERSION
		625	} else {
		626	if (@_ > 0) {
		627	return undef if VERSION_v lt $_[0];
		628	if (@_ > 1) {
		629	return undef if VERSION_v ge $_[1];
		630	}
		631	}
		632
		633	VERSION_v
		634	}
		635	}
		636
172	=head3 CONTROLLING THE NUMBER OF THREADS	637	=head3 CONTROLLING THE NUMBER OF THREADS
173		638
		639	=over 4
		640
174	=item BDB::min_parallel $nthreads	641	=item BDB::min_parallel $nthreads
175		642
176	Set the minimum number of AIO threads to C<$nthreads>. The current	643	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	644	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	645	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	646	however, is unlimited).
180		647
181	BDB starts threads only on demand, when an AIO request is queued and	648	BDB starts threads only on demand, when an BDB request is queued and
182	no free thread exists. Please note that queueing up a hundred requests can	649	no free thread exists. Please note that queueing up a hundred requests can
183	create demand for a hundred threads, even if it turns out that everything	650	create demand for a hundred threads, even if it turns out that everything
184	is in the cache and could have been processed faster by a single thread.	651	is in the cache and could have been processed faster by a single thread.
185		652
186	It is recommended to keep the number of threads relatively low, as some	653	It is recommended to keep the number of threads relatively low, as some
…		…
191	Under most circumstances you don't need to call this function, as the	658	Under most circumstances you don't need to call this function, as the
192	module selects a default that is suitable for low to moderate load.	659	module selects a default that is suitable for low to moderate load.
193		660
194	=item BDB::max_parallel $nthreads	661	=item BDB::max_parallel $nthreads
195		662
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	663	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	664	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	665	them. This function blocks until the limit is reached.
199		666
200	While C<$nthreads> are zero, aio requests get queued but not executed	667	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	668	until the number of threads has been increased again.
…		…
236		703
237	You can still queue as many requests as you want. Therefore,	704	You can still queue as many requests as you want. Therefore,
238	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	705	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
239	as a stop gap to shield against fatal memory overflow (with large values).	706	as a stop gap to shield against fatal memory overflow (with large values).
240		707
		708	=item BDB::set_sync_prepare $cb
		709
		710	Sets a callback that is called whenever a request is created without an
		711	explicit callback. It has to return two code references. The first is used
		712	as the request callback (it should save the return status), and the second
		713	is called to wait until the first callback has been called (it must set
		714	C<$!> to the return status).
		715
		716	This mechanism can be used to include BDB into other event mechanisms,
		717	such as L<AnyEvent::BDB> or L<Coro::BDB>.
		718
		719	The default implementation works like this:
		720
		721	sub {
		722	my $status;
		723	(
		724	sub { $status = $! },
		725	sub { BDB::poll while !defined $status; $! = $status },
		726	)
		727	}
		728
		729	It simply blocks the process till the request has finished and then sets
		730	C<$!> to the return value. This means that if you don't use a callback,
		731	BDB will simply fall back to synchronous operations.
		732
		733	=back
		734
241	=head3 STATISTICAL INFORMATION	735	=head3 STATISTICAL INFORMATION
		736
		737	=over 4
242		738
243	=item BDB::nreqs	739	=item BDB::nreqs
244		740
245	Returns the number of requests currently in the ready, execute or pending	741	Returns the number of requests currently in the ready, execute or pending
246	states (i.e. for which their callback has not been invoked yet).	742	states (i.e. for which their callback has not been invoked yet).
…		…
262		758
263	=back	759	=back
264		760
265	=cut	761	=cut
266		762
		763	set_sync_prepare {
		764	my $status;
		765	(
		766	sub {
		767	$status = $!;
		768	},
		769	sub {
		770	BDB::poll while !defined $status;
		771	$! = $status;
		772	},
		773	)
		774	};
		775
267	min_parallel 8;	776	min_parallel 8;
268		777
269	END { flush }	778	END { flush }
270		779
271	1;	780	1;
272		781
273	=head2 FORK BEHAVIOUR	782	=head2 FORK BEHAVIOUR
274		783
275	This module should do "the right thing" when the process using it forks:	784	This module should do "the right thing" when the process using it forks:
276		785
277	Before the fork, IO::AIO enters a quiescent state where no requests	786	Before the fork, BDB enters a quiescent state where no requests
278	can be added in other threads and no results will be processed. After	787	can be added in other threads and no results will be processed. After
279	the fork the parent simply leaves the quiescent state and continues	788	the fork the parent simply leaves the quiescent state and continues
280	request/result processing, while the child frees the request/result queue	789	request/result processing, while the child frees the request/result queue
281	(so that the requests started before the fork will only be handled in the	790	(so that the requests started before the fork will only be handled in the
282	parent). Threads will be started on demand until the limit set in the	791	parent). Threads will be started on demand until the limit set in the
283	parent process has been reached again.	792	parent process has been reached again.
284		793
285	In short: the parent will, after a short pause, continue as if fork had	794	In short: the parent will, after a short pause, continue as if fork had
286	not been called, while the child will act as if IO::AIO has not been used	795	not been called, while the child will act as if BDB has not been used
287	yet.	796	yet.
		797
		798	Win32 note: there is no fork on win32, and perls emulation of it is too
		799	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		800	yet, switch to a more capable platform.
288		801
289	=head2 MEMORY USAGE	802	=head2 MEMORY USAGE
290		803
291	Per-request usage:	804	Per-request usage:
292		805
…		…
294	bytes of memory. In addition, stat requests need a stat buffer (possibly	807	bytes of memory. In addition, stat requests need a stat buffer (possibly
295	a few hundred bytes), readdir requires a result buffer and so on. Perl	808	a few hundred bytes), readdir requires a result buffer and so on. Perl
296	scalars and other data passed into aio requests will also be locked and	809	scalars and other data passed into aio requests will also be locked and
297	will consume memory till the request has entered the done state.	810	will consume memory till the request has entered the done state.
298		811
299	This is now awfully much, so queuing lots of requests is not usually a	812	This is not awfully much, so queuing lots of requests is not usually a
300	problem.	813	problem.
301		814
302	Per-thread usage:	815	Per-thread usage:
303		816
304	In the execution phase, some aio requests require more memory for	817	In the execution phase, some aio requests require more memory for
305	temporary buffers, and each thread requires a stack and other data	818	temporary buffers, and each thread requires a stack and other data
306	structures (usually around 16k-128k, depending on the OS).	819	structures (usually around 16k-128k, depending on the OS).
307		820
308	=head1 KNOWN BUGS	821	=head1 KNOWN BUGS
309		822
310	Known bugs will be fixed in the next release.	823	Known bugs will be fixed in the next release, except:
		824
		825	If you use a transaction in any request, and the request returns
		826	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		827	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		828	above.
311		829
312	=head1 SEE ALSO	830	=head1 SEE ALSO
313		831
314	L<Coro::AIO>.	832	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		833	syntax), L<IO::AIO> (nice to have).
315		834
316	=head1 AUTHOR	835	=head1 AUTHOR
317		836
318	Marc Lehmann <schmorp@schmorp.de>	837	Marc Lehmann <schmorp@schmorp.de>
319	http://home.schmorp.de/	838	http://home.schmorp.de/

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Comparing BDB/BDB.pm (file contents): Revision 1.2 by root, Mon Feb 5 20:21:38 2007 UTC vs. Revision 1.48 by root, Tue Jul 29 03:33:16 2008 UTC

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Comparing BDB/BDB.pm (file contents):
Revision 1.2 by root, Mon Feb 5 20:21:38 2007 UTC vs.
Revision 1.48 by root, Tue Jul 29 03:33:16 2008 UTC