[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 1.51 by root, Mon Sep 29 02:59:08 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.
…		…
66	no warnings;	108	no warnings;
67	use strict 'vars';	109	use strict 'vars';
68		110
69	use base 'Exporter';	111	use base 'Exporter';
70		112
		113	our $VERSION;
		114
71	BEGIN {	115	BEGIN {
72	our $VERSION = '0.1';	116	$VERSION = '1.801';
73		117
74	our @BDB_REQ = qw(	118	our @BDB_REQ = qw(
75	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect	119	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
76	db_env_memp_sync db_env_memp_trickle	120	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	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
78	db_txn_commit db_txn_abort	123	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	124	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	125	db_sequence_open db_sequence_close
81	db_sequence_get db_sequence_remove	126	db_sequence_get db_sequence_remove
82	);	127	);
83	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));	128	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
…		…
90		135
91	require XSLoader;	136	require XSLoader;
92	XSLoader::load ("BDB", $VERSION);	137	XSLoader::load ("BDB", $VERSION);
93	}	138	}
94		139
		140	=head2 WIN32 FILENAMES/DATABASE NAME MESS
		141
		142	Perl on Win32 supports only ASCII filenames (the reason is that it abuses
		143	an internal flag to store wether a filename is Unicode or ANSI, but that
		144	flag is used for somethign else in the perl core, so there is no way to
		145	detect wether a filename is ANSI or Unicode-encoded). The BDB module
		146	tries to work around this issue by assuming that the filename is an ANSI
		147	filename and BDB was built for unicode support.
		148
		149	=head2 BERKELEYDB FUNCTIONS
		150
		151	All of these are functions. The create functions simply return a new
		152	object and never block. All the remaining functions take an optional
		153	callback as last argument. If it is missing, then the function will be
		154	executed synchronously. In both cases, C<$!> 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
95	=head2 SUPPORT FUNCTIONS	472	=head2 SUPPORT FUNCTIONS
96		473
97	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	474	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
98		475
99	=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<$!>.
100		485
101	=item $fileno = BDB::poll_fileno	486	=item $fileno = BDB::poll_fileno
102		487
103	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
104	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
…		…
143	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
144	time.	529	time.
145		530
146	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.
147		532
148	Example: Install an Event watcher that automatically calls	533	Example: Install an EV watcher that automatically calls
149	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
150	program get the CPU sometimes even under high AIO load.	535	program get the CPU sometimes even under high load.
151		536
152	# 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
153	BDB::max_poll_time 0.1;	538	BDB::max_poll_time 0.1;
154		539
155	# use a low priority so other tasks have priority	540	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		541
160	=item BDB::poll_wait	542	=item BDB::poll_wait
161		543
162	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
163	phase, wait till the result filehandle becomes ready for reading (simply	545	phase, wait till the result filehandle becomes ready for reading (simply
…		…
175		557
176	BDB::poll_wait, BDB::poll_cb	558	BDB::poll_wait, BDB::poll_cb
177		559
178	=item BDB::flush	560	=item BDB::flush
179		561
180	Wait till all outstanding AIO requests have been handled.	562	Wait till all outstanding BDB requests have been handled.
181		563
182	Strictly equivalent to:	564	Strictly equivalent to:
183		565
184	BDB::poll_wait, BDB::poll_cb	566	BDB::poll_wait, BDB::poll_cb
185	while BDB::nreqs;	567	while BDB::nreqs;
186		568
187	=back	569	=back
188		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
189	=head3 CONTROLLING THE NUMBER OF THREADS	637	=head3 CONTROLLING THE NUMBER OF THREADS
190		638
191	=over 4	639	=over 4
192		640
193	=item BDB::min_parallel $nthreads	641	=item BDB::min_parallel $nthreads
194		642
195	Set the minimum number of AIO threads to C<$nthreads>. The current	643	Set the minimum number of BDB threads to C<$nthreads>. The current
196	default is C<8>, which means eight asynchronous operations can execute	644	default is C<8>, which means eight asynchronous operations can execute
197	concurrently at any one time (the number of outstanding requests,	645	concurrently at any one time (the number of outstanding requests,
198	however, is unlimited).	646	however, is unlimited).
199		647
200	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
201	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
202	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
203	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.
204		652
205	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
…		…
210	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
211	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.
212		660
213	=item BDB::max_parallel $nthreads	661	=item BDB::max_parallel $nthreads
214		662
215	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	663	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
216	specified number of threads are currently running, this function kills	664	specified number of threads are currently running, this function kills
217	them. This function blocks until the limit is reached.	665	them. This function blocks until the limit is reached.
218		666
219	While C<$nthreads> are zero, aio requests get queued but not executed	667	While C<$nthreads> are zero, aio requests get queued but not executed
220	until the number of threads has been increased again.	668	until the number of threads has been increased again.
…		…
255		703
256	You can still queue as many requests as you want. Therefore,	704	You can still queue as many requests as you want. Therefore,
257	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
258	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).
259		707
260	=item BDB::set_sync_prepare $cb	708	=item $old_cb = BDB::set_sync_prepare $cb
261		709
262	Sets a callback that is called whenever a request is created without an	710	Sets a callback that is called whenever a request is created without an
263	explicit callback. It has to return two code references. The first is used	711	explicit callback. It has to return two code references. The first is used
264	as the request callback, and the second is called to wait until the first	712	as the request callback (it should save the return status), and the second
265	callback has been called. The default implementation works like this:	713	is called to wait until the first callback has been called (it must set
		714	C<$!> to the return status).
		715
		716	This mechanism can be used to include BDB into other event mechanisms,
		717	such as L<Coro::BDB>.
		718
		719	To allow other, callback-based, events to be executed while callback-less
		720	ones are run, you could use this sync prepare function:
266		721
267	sub {	722	sub {
268	my $status;	723	my $status;
269	(	724	(
270	sub { $status = $! },	725	sub { $status = $! },
271	sub { BDB::poll while !defined $status; $! = $status },	726	sub { BDB::poll while !defined $status; $! = $status },
272	)	727	)
273	}	728	}
274		729
		730	It works by polling for results till the request has finished and then
		731	sets C<$!> to the return value. This means that if you don't use a
		732	callback, BDB would simply fall back to synchronous operations.
		733
		734	By default, or if the sync prepare function is set to C<undef>, is to
		735	execute callback-less BDB requests in the foreground thread, setting C<$!>
		736	to the return value, without polling for other events.
		737
275	=back	738	=back
276		739
277	=head3 STATISTICAL INFORMATION	740	=head3 STATISTICAL INFORMATION
278		741
279	=over 4	742	=over 4
…		…
300		763
301	=back	764	=back
302		765
303	=cut	766	=cut
304		767
305	set_sync_prepare {	768	set_sync_prepare (undef);
306	my $status;
307	(
308	sub {
309	$status = $!;
310	},
311	sub {
312	BDB::poll while !defined $status;
313	$! = $status;
314	},
315	)
316	};
317		769
318	min_parallel 8;	770	min_parallel 8;
319		771
320	END { flush }	772	END { flush }
321		773
…		…
323		775
324	=head2 FORK BEHAVIOUR	776	=head2 FORK BEHAVIOUR
325		777
326	This module should do "the right thing" when the process using it forks:	778	This module should do "the right thing" when the process using it forks:
327		779
328	Before the fork, IO::AIO enters a quiescent state where no requests	780	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	781	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	782	the fork the parent simply leaves the quiescent state and continues
331	request/result processing, while the child frees the request/result queue	783	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	784	(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	785	parent). Threads will be started on demand until the limit set in the
334	parent process has been reached again.	786	parent process has been reached again.
335		787
336	In short: the parent will, after a short pause, continue as if fork had	788	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	789	not been called, while the child will act as if BDB has not been used
338	yet.	790	yet.
		791
		792	Win32 note: there is no fork on win32, and perls emulation of it is too
		793	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		794	yet, switch to a more capable platform.
339		795
340	=head2 MEMORY USAGE	796	=head2 MEMORY USAGE
341		797
342	Per-request usage:	798	Per-request usage:
343		799
…		…
345	bytes of memory. In addition, stat requests need a stat buffer (possibly	801	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	802	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	803	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.	804	will consume memory till the request has entered the done state.
349		805
350	This is now awfully much, so queuing lots of requests is not usually a	806	This is not awfully much, so queuing lots of requests is not usually a
351	problem.	807	problem.
352		808
353	Per-thread usage:	809	Per-thread usage:
354		810
355	In the execution phase, some aio requests require more memory for	811	In the execution phase, some aio requests require more memory for
356	temporary buffers, and each thread requires a stack and other data	812	temporary buffers, and each thread requires a stack and other data
357	structures (usually around 16k-128k, depending on the OS).	813	structures (usually around 16k-128k, depending on the OS).
358		814
359	=head1 KNOWN BUGS	815	=head1 KNOWN BUGS
360		816
361	Known bugs will be fixed in the next release.	817	Known bugs will be fixed in the next release, except:
		818
		819	If you use a transaction in any request, and the request returns
		820	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		821	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		822	above.
362		823
363	=head1 SEE ALSO	824	=head1 SEE ALSO
364		825
365	L<Coro::AIO>.	826	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		827	syntax), L<IO::AIO> (nice to have).
366		828
367	=head1 AUTHOR	829	=head1 AUTHOR
368		830
369	Marc Lehmann <schmorp@schmorp.de>	831	Marc Lehmann <schmorp@schmorp.de>
370	http://home.schmorp.de/	832	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 1.51 by root, Mon Sep 29 02:59:08 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 1.51 by root, Mon Sep 29 02:59:08 2008 UTC