[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 1.38 by root, Mon Jul 7 22:11:04 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 = '1.5';
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)
		284	$env->set_errfile (FILE *errfile = 0)
		285	$env->set_msgfile (FILE *msgfile = 0)
		286	$int = $env->set_verbose (U32 which, int onoff = 1)
		287	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		288	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		289	$int = $env->set_mp_max_openfd (int maxopenfd);
		290	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		291	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		292	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		293	$int = $env->set_lk_max_lockers (U32 max)
		294	$int = $env->set_lk_max_locks (U32 max)
		295	$int = $env->set_lk_max_objects (U32 max)
		296	$int = $env->set_lg_bsize (U32 max)
		297	$int = $env->set_lg_max (U32 max)
		298	$int = $env->mutex_set_increment (U32 increment)
		299	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		300	$int = $env->mutex_set_max (U32 max)
		301	$int = $env->mutex_set_align (U32 align)
		302
		303	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		304	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		305
		306	=head4 Example:
		307
		308	use AnyEvent;
		309	use BDB;
		310
		311	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		312	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		313
		314	BDB::min_parallel 8;
		315
		316	my $env = db_env_create;
		317
		318	mkdir "bdtest", 0700;
		319	db_env_open
		320	$env,
		321	"bdtest",
		322	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		323	0600;
		324
		325	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		326
		327
		328	=head3 DB/database methods
		329
		330	Methods available on DB/$db handles:
		331
		332	DESTROY (DB_ornull *db)
		333	CODE:
		334	if (db)
		335	{
		336	SV env = (SV )db->app_private;
		337	db->close (db, 0);
		338	SvREFCNT_dec (env);
		339	}
		340
		341	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		342	$int = $db->set_flags (U32 flags)
		343	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		344	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		345	Hash: DUP DUPSORT
		346	Queue: INORDER
		347	Recno: RENUMBER SNAPSHOT
		348
		349	$int = $db->set_encrypt (const char *password, U32 flags)
		350	$int = $db->set_lorder (int lorder)
		351	$int = $db->set_bt_minkey (U32 minkey)
		352	$int = $db->set_re_delim (int delim)
		353	$int = $db->set_re_pad (int re_pad)
		354	$int = $db->set_re_source (char *source)
		355	$int = $db->set_re_len (U32 re_len)
		356	$int = $db->set_h_ffactor (U32 h_ffactor)
		357	$int = $db->set_h_nelem (U32 h_nelem)
		358	$int = $db->set_q_extentsize (U32 extentsize)
		359
		360	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		361	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		362	$seq = $db->sequence (U32 flags = 0)
		363
		364	=head4 Example:
		365
		366	my $db = db_create $env;
		367	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		368
		369	for (1..1000) {
		370	db_put $db, undef, "key $_", "data $_";
		371
		372	db_key_range $db, undef, "key $_", my $keyrange;
		373	my ($lt, $eq, $gt) = @$keyrange;
		374	}
		375
		376	db_del $db, undef, "key $_" for 1..1000;
		377
		378	db_sync $db;
		379
		380
		381	=head3 DB_TXN/transaction methods
		382
		383	Methods available on DB_TXN/$txn handles:
		384
		385	DESTROY (DB_TXN_ornull *txn)
		386	CODE:
		387	if (txn)
		388	txn->abort (txn);
		389
		390	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		391	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		392
		393	$bool = $txn->failed
		394	# see db_txn_finish documentation, above
		395
		396
		397	=head3 DBC/cursor methods
		398
		399	Methods available on DBC/$dbc handles:
		400
		401	DESTROY (DBC_ornull *dbc)
		402	CODE:
		403	if (dbc)
		404	dbc->c_close (dbc);
		405
		406	$int = $cursor->set_priority ($priority = PRIORITY_*)
		407
		408	=head4 Example:
		409
		410	my $c = $db->cursor;
		411
		412	for (;;) {
		413	db_c_get $c, my $key, my $data, BDB::NEXT;
		414	warn "<$!,$key,$data>";
		415	last if $!;
		416	}
		417
		418	db_c_close $c;
		419
		420
		421	=head3 DB_SEQUENCE/sequence methods
		422
		423	Methods available on DB_SEQUENCE/$seq handles:
		424
		425	DESTROY (DB_SEQUENCE_ornull *seq)
		426	CODE:
		427	if (seq)
		428	seq->close (seq, 0);
		429
		430	$int = $seq->initial_value (db_seq_t value)
		431	$int = $seq->set_cachesize (U32 size)
		432	$int = $seq->set_flags (U32 flags)
		433	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		434	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		435
		436	=head4 Example:
		437
		438	my $seq = $db->sequence;
		439
		440	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		441	db_sequence_get $seq, undef, 1, my $value;
		442
		443
95	=head2 SUPPORT FUNCTIONS	444	=head2 SUPPORT FUNCTIONS
96		445
97	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	446	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
98		447
99	=over 4	448	=over 4
		449
		450	=item $msg = BDB::strerror [$errno]
		451
		452	Returns the string corresponding to the given errno value. If no argument
		453	is given, use C<$!>.
		454
		455	Note that the BDB module also patches the C<$!> variable directly, so you
		456	should be able to get a bdb error string by simply stringifying C<$!>.
100		457
101	=item $fileno = BDB::poll_fileno	458	=item $fileno = BDB::poll_fileno
102		459
103	Return the I<request result pipe file descriptor>. This filehandle must be	460	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	461	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	500	interactiveness when perl is not fast enough to process all requests in
144	time.	501	time.
145		502
146	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	503	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
147		504
148	Example: Install an Event watcher that automatically calls	505	Example: Install an EV watcher that automatically calls
149	BDB::poll_cb with low priority, to ensure that other parts of the	506	BDB::poll_cb with low priority, to ensure that other parts of the
150	program get the CPU sometimes even under high AIO load.	507	program get the CPU sometimes even under high load.
151		508
152	# try not to spend much more than 0.1s in poll_cb	509	# try not to spend much more than 0.1s in poll_cb
153	BDB::max_poll_time 0.1;	510	BDB::max_poll_time 0.1;
154		511
155	# use a low priority so other tasks have priority	512	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		513
160	=item BDB::poll_wait	514	=item BDB::poll_wait
161		515
162	If there are any outstanding requests and none of them in the result	516	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	517	phase, wait till the result filehandle becomes ready for reading (simply
…		…
175		529
176	BDB::poll_wait, BDB::poll_cb	530	BDB::poll_wait, BDB::poll_cb
177		531
178	=item BDB::flush	532	=item BDB::flush
179		533
180	Wait till all outstanding AIO requests have been handled.	534	Wait till all outstanding BDB requests have been handled.
181		535
182	Strictly equivalent to:	536	Strictly equivalent to:
183		537
184	BDB::poll_wait, BDB::poll_cb	538	BDB::poll_wait, BDB::poll_cb
185	while BDB::nreqs;	539	while BDB::nreqs;
…		…
190		544
191	=over 4	545	=over 4
192		546
193	=item BDB::min_parallel $nthreads	547	=item BDB::min_parallel $nthreads
194		548
195	Set the minimum number of AIO threads to C<$nthreads>. The current	549	Set the minimum number of BDB threads to C<$nthreads>. The current
196	default is C<8>, which means eight asynchronous operations can execute	550	default is C<8>, which means eight asynchronous operations can execute
197	concurrently at any one time (the number of outstanding requests,	551	concurrently at any one time (the number of outstanding requests,
198	however, is unlimited).	552	however, is unlimited).
199		553
200	BDB starts threads only on demand, when an AIO request is queued and	554	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	555	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	556	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.	557	is in the cache and could have been processed faster by a single thread.
204		558
205	It is recommended to keep the number of threads relatively low, as some	559	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	564	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.	565	module selects a default that is suitable for low to moderate load.
212		566
213	=item BDB::max_parallel $nthreads	567	=item BDB::max_parallel $nthreads
214		568
215	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	569	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
216	specified number of threads are currently running, this function kills	570	specified number of threads are currently running, this function kills
217	them. This function blocks until the limit is reached.	571	them. This function blocks until the limit is reached.
218		572
219	While C<$nthreads> are zero, aio requests get queued but not executed	573	While C<$nthreads> are zero, aio requests get queued but not executed
220	until the number of threads has been increased again.	574	until the number of threads has been increased again.
…		…
259		613
260	=item BDB::set_sync_prepare $cb	614	=item BDB::set_sync_prepare $cb
261		615
262	Sets a callback that is called whenever a request is created without an	616	Sets a callback that is called whenever a request is created without an
263	explicit callback. It has to return two code references. The first is used	617	explicit callback. It has to return two code references. The first is used
264	as the request callback, and the second is called to wait until the first	618	as the request callback (it should save the return status), and the second
		619	is called to wait until the first callback has been called (it must set
		620	C<$!> to the return status).
		621
		622	This mechanism can be used to include BDB into other event mechanisms,
		623	such as L<AnyEvent::BDB> or L<Coro::BDB>.
		624
265	callback has been called. The default implementation works like this:	625	The default implementation works like this:
266		626
267	sub {	627	sub {
268	my $status;	628	my $status;
269	(	629	(
270	sub { $status = $! },	630	sub { $status = $! },
271	sub { BDB::poll while !defined $status; $! = $status },	631	sub { BDB::poll while !defined $status; $! = $status },
272	)	632	)
273	}	633	}
		634
		635	It simply blocks the process till the request has finished and then sets
		636	C<$!> to the return value. This means that if you don't use a callback,
		637	BDB will simply fall back to synchronous operations.
274		638
275	=back	639	=back
276		640
277	=head3 STATISTICAL INFORMATION	641	=head3 STATISTICAL INFORMATION
278		642
…		…
323		687
324	=head2 FORK BEHAVIOUR	688	=head2 FORK BEHAVIOUR
325		689
326	This module should do "the right thing" when the process using it forks:	690	This module should do "the right thing" when the process using it forks:
327		691
328	Before the fork, IO::AIO enters a quiescent state where no requests	692	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	693	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	694	the fork the parent simply leaves the quiescent state and continues
331	request/result processing, while the child frees the request/result queue	695	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	696	(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	697	parent). Threads will be started on demand until the limit set in the
334	parent process has been reached again.	698	parent process has been reached again.
335		699
336	In short: the parent will, after a short pause, continue as if fork had	700	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	701	not been called, while the child will act as if BDB has not been used
338	yet.	702	yet.
		703
		704	Win32 note: there is no fork on win32, and perls emulation of it is too
		705	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		706	yet, switch to a more capable platform.
339		707
340	=head2 MEMORY USAGE	708	=head2 MEMORY USAGE
341		709
342	Per-request usage:	710	Per-request usage:
343		711
…		…
345	bytes of memory. In addition, stat requests need a stat buffer (possibly	713	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	714	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	715	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.	716	will consume memory till the request has entered the done state.
349		717
350	This is now awfully much, so queuing lots of requests is not usually a	718	This is not awfully much, so queuing lots of requests is not usually a
351	problem.	719	problem.
352		720
353	Per-thread usage:	721	Per-thread usage:
354		722
355	In the execution phase, some aio requests require more memory for	723	In the execution phase, some aio requests require more memory for
356	temporary buffers, and each thread requires a stack and other data	724	temporary buffers, and each thread requires a stack and other data
357	structures (usually around 16k-128k, depending on the OS).	725	structures (usually around 16k-128k, depending on the OS).
358		726
359	=head1 KNOWN BUGS	727	=head1 KNOWN BUGS
360		728
361	Known bugs will be fixed in the next release.	729	Known bugs will be fixed in the next release, except:
		730
		731	If you use a transaction in any request, and the request returns
		732	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		733	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		734	above.
362		735
363	=head1 SEE ALSO	736	=head1 SEE ALSO
364		737
365	L<Coro::AIO>.	738	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		739	syntax), L<IO::AIO> (nice to have).
366		740
367	=head1 AUTHOR	741	=head1 AUTHOR
368		742
369	Marc Lehmann <schmorp@schmorp.de>	743	Marc Lehmann <schmorp@schmorp.de>
370	http://home.schmorp.de/	744	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 1.38 by root, Mon Jul 7 22:11:04 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 1.38 by root, Mon Jul 7 22:11:04 2008 UTC