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

Comparing BDB/BDB.pm (file contents):
Revision 1.6 by root, Sun Feb 11 22:07:23 2007 UTC vs.
Revision 1.26 by root, Tue Dec 11 01:45:16 2007 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	# automatic result processing with AnyEvent:
		30	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		31	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		32
		33	# automatic result processing with EV:
		34	my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
		35
		36	# with Glib:
		37	add_watch Glib::IO BDB::poll_fileno,
		38	in => sub { BDB::poll_cb; 1 };
		39
		40	# or simply flush manually
		41	BDB::flush;
		42
		43
9	=head1 DESCRIPTION	44	=head1 DESCRIPTION
10		45
11	=head2 EXAMPLE	46	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
		47	The BDB API is very similar to the C API (the translation has been very faithful).
		48
		49	See also the example sections in the document below and possibly the eg/
		50	subdirectory of the BDB distribution. Last not least see the IO::AIO
		51	documentation, as that module uses almost the same asynchronous request
		52	model as this module.
		53
		54	I know this is woefully inadequate documentation. Send a patch!
		55
12		56
13	=head1 REQUEST ANATOMY AND LIFETIME	57	=head1 REQUEST ANATOMY AND LIFETIME
14		58
15	Every request method creates a request. which is a C data structure not	59	Every request method creates a request. which is a C data structure not
16	directly visible to Perl.	60	directly visible to Perl.
…		…
63	use strict 'vars';	107	use strict 'vars';
64		108
65	use base 'Exporter';	109	use base 'Exporter';
66		110
67	BEGIN {	111	BEGIN {
68	our $VERSION = '0.1';	112	our $VERSION = '1.3';
69		113
70	our @BDB_REQ = qw(	114	our @BDB_REQ = qw(
71	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect	115	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
72	db_env_memp_sync db_env_memp_trickle	116	db_env_memp_sync db_env_memp_trickle
73	db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range	117	db_open db_close db_compact db_sync db_upgrade
		118	db_put db_get db_pget db_del db_key_range
74	db_txn_commit db_txn_abort	119	db_txn_commit db_txn_abort db_txn_finish
75	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del	120	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
76	db_sequence_open db_sequence_close	121	db_sequence_open db_sequence_close
77	db_sequence_get db_sequence_remove	122	db_sequence_get db_sequence_remove
78	);	123	);
79	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));	124	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
…		…
86		131
87	require XSLoader;	132	require XSLoader;
88	XSLoader::load ("BDB", $VERSION);	133	XSLoader::load ("BDB", $VERSION);
89	}	134	}
90		135
		136	=head2 BERKELEYDB FUNCTIONS
		137
		138	All of these are functions. The create functions simply return a new
		139	object and never block. All the remaining functions all take an optional
		140	callback as last argument. If it is missing, then the function will be
		141	executed synchronously. In both cases, C<$!> will reflect the return value
		142	of the function.
		143
		144	BDB functions that cannot block (mostly functions that manipulate
		145	settings) are method calls on the relevant objects, so the rule of thumb
		146	is: if its a method, its not blocking, if its a function, it takes a
		147	callback as last argument.
		148
		149	In the following, C<$int> signifies an integer return value,
		150	C<octetstring> is a "binary string" (i.e. a perl string with no character
		151	indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
		152	integer, C<NV> is a floating point value.
		153
		154	The C<SV *> types are generic perl scalars (for input and output of data
		155	values), and the C<SV *callback> is the optional callback function to call
		156	when the request is completed.
		157
		158	The various C<DB_ENV> etc. arguments are handles return by
		159	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		160	appended C<_ornull> this means they are optional and you can pass C<undef>
		161	for them, resulting a NULL pointer on the C level.
		162
		163	=head3 BDB functions
		164
		165	Functions in the BDB namespace, exported by default:
		166
		167	$env = db_env_create (U32 env_flags = 0)
		168	flags: RPCCLIENT
		169
		170	db_env_open (DB_ENV env, octetstring db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		171	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
		172	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		173	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		174	flags: FORCE
		175	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		176	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		177	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		178	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		179
		180	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		181	flags: XA_CREATE
		182
		183	db_open (DB db, DB_TXN_ornull txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		184	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		185	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		186	flags: DB_NOSYNC
		187	db_upgrade (DB db, octetstring file, U32 flags = 0, SV callback = &PL_sv_undef)
		188	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)
		189	flags: FREELIST_ONLY FREE_SPACE
		190	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		191	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		192	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		193	flags: APPEND NODUPDATA NOOVERWRITE
		194	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		195	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		196	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		197	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		198	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		199	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		200	flags: TXN_NOSYNC TXN_SYNC
		201	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		202
		203	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		204	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		205	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		206	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		207	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		208	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
		209	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		210	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		211
		212	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		213	flags: CREATE EXCL
		214	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		215	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)
		216	flags: TXN_NOSYNC
		217	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		218	flags: TXN_NOSYNC
		219
		220	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		221
		222	This is not actually a Berkeley DB function but a BDB module
		223	extension. The background for this exytension is: It is very annoying to
		224	have to check every single BDB function for error returns and provide a
		225	codepath out of your transaction. While the BDB module still makes this
		226	possible, it contains the following extensions:
		227
		228	When a transaction-protected function returns any operating system
		229	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		230	transaction. This flag is also set by Berkeley DB functions themselves
		231	when an operation fails with LOCK_DEADLOCK, and it causes all further
		232	operations on that transaction (including C<db_txn_commit>) to fail.
		233
		234	The C<db_txn_finish> request will look at this flag, and, if it is set,
		235	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		236	if it isn't set to something else yet). If it isn't set, it will call
		237	C<db_txn_commit> and return the error normally.
		238
		239	How to use this? Easy: just write your transaction normally:
		240
		241	my $txn = $db_env->txn_begin;
		242	db_get $db, $txn, "key", my $data;
		243	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		244	db_txn_finish $txn;
		245	die "transaction failed" if $!;
		246
		247	That is, handle only the expected errors. If something unexpected happens
		248	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		249	requests (db_put in this case) will simply be skipped (they will fail with
		250	LOCK_DEADLOCK) and the transaction will be aborted.
		251
		252	You can use the C<< $txn->failed >> method to check wether a transaction
		253	has failed in this way and abort further processing (excluding
		254	C<db_txn_finish>).
		255
		256	=head3 DB_ENV/database environment methods
		257
		258	Methods available on DB_ENV/$env handles:
		259
		260	DESTROY (DB_ENV_ornull *env)
		261	CODE:
		262	if (env)
		263	env->close (env, 0);
		264
		265	$int = $env->set_data_dir (const char *dir)
		266	$int = $env->set_tmp_dir (const char *dir)
		267	$int = $env->set_lg_dir (const char *dir)
		268	$int = $env->set_shm_key (long shm_key)
		269	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		270	$int = $env->set_flags (U32 flags, int onoff)
		271	$env->set_errfile (FILE *errfile = 0)
		272	$env->set_msgfile (FILE *msgfile = 0)
		273	$int = $env->set_verbose (U32 which, int onoff = 1)
		274	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		275	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		276	$int = $env->set_mp_max_openfd (int maxopenfd);
		277	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		278	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		279	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		280	$int = $env->set_lk_max_lockers (U32 max)
		281	$int = $env->set_lk_max_locks (U32 max)
		282	$int = $env->set_lk_max_objects (U32 max)
		283	$int = $env->set_lg_bsize (U32 max)
		284	$int = $env->set_lg_max (U32 max)
		285	$int = $env->mutex_set_increment (U32 increment)
		286	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		287	$int = $env->mutex_set_max (U32 max)
		288	$int = $env->mutex_set_align (U32 align)
		289
		290	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		291	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		292
		293	=head4 Example:
		294
		295	use AnyEvent;
		296	use BDB;
		297
		298	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		299	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		300
		301	BDB::min_parallel 8;
		302
		303	my $env = db_env_create;
		304
		305	mkdir "bdtest", 0700;
		306	db_env_open
		307	$env,
		308	"bdtest",
		309	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		310	0600;
		311
		312	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		313
		314
		315	=head3 DB/database methods
		316
		317	Methods available on DB/$db handles:
		318
		319	DESTROY (DB_ornull *db)
		320	CODE:
		321	if (db)
		322	{
		323	SV env = (SV )db->app_private;
		324	db->close (db, 0);
		325	SvREFCNT_dec (env);
		326	}
		327
		328	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		329	$int = $db->set_flags (U32 flags)
		330	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		331	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		332	Hash: DUP DUPSORT
		333	Queue: INORDER
		334	Recno: RENUMBER SNAPSHOT
		335
		336	$int = $db->set_encrypt (const char *password, U32 flags)
		337	$int = $db->set_lorder (int lorder)
		338	$int = $db->set_bt_minkey (U32 minkey)
		339	$int = $db->set_re_delim (int delim)
		340	$int = $db->set_re_pad (int re_pad)
		341	$int = $db->set_re_source (char *source)
		342	$int = $db->set_re_len (U32 re_len)
		343	$int = $db->set_h_ffactor (U32 h_ffactor)
		344	$int = $db->set_h_nelem (U32 h_nelem)
		345	$int = $db->set_q_extentsize (U32 extentsize)
		346
		347	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		348	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		349	$seq = $db->sequence (U32 flags = 0)
		350
		351	=head4 Example:
		352
		353	my $db = db_create $env;
		354	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		355
		356	for (1..1000) {
		357	db_put $db, undef, "key $_", "data $_";
		358
		359	db_key_range $db, undef, "key $_", my $keyrange;
		360	my ($lt, $eq, $gt) = @$keyrange;
		361	}
		362
		363	db_del $db, undef, "key $_" for 1..1000;
		364
		365	db_sync $db;
		366
		367
		368	=head3 DB_TXN/transaction methods
		369
		370	Methods available on DB_TXN/$txn handles:
		371
		372	DESTROY (DB_TXN_ornull *txn)
		373	CODE:
		374	if (txn)
		375	txn->abort (txn);
		376
		377	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		378	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		379
		380	$bool = $txn->failed
		381	# see db_txn_finish documentation, above
		382
		383
		384	=head3 DBC/cursor methods
		385
		386	Methods available on DBC/$dbc handles:
		387
		388	DESTROY (DBC_ornull *dbc)
		389	CODE:
		390	if (dbc)
		391	dbc->c_close (dbc);
		392
		393	=head4 Example:
		394
		395	my $c = $db->cursor;
		396
		397	for (;;) {
		398	db_c_get $c, my $key, my $data, BDB::NEXT;
		399	warn "<$!,$key,$data>";
		400	last if $!;
		401	}
		402
		403	db_c_close $c;
		404
		405
		406	=head3 DB_SEQUENCE/sequence methods
		407
		408	Methods available on DB_SEQUENCE/$seq handles:
		409
		410	DESTROY (DB_SEQUENCE_ornull *seq)
		411	CODE:
		412	if (seq)
		413	seq->close (seq, 0);
		414
		415	$int = $seq->initial_value (db_seq_t value)
		416	$int = $seq->set_cachesize (U32 size)
		417	$int = $seq->set_flags (U32 flags)
		418	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		419	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		420
		421	=head4 Example:
		422
		423	my $seq = $db->sequence;
		424
		425	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		426	db_sequence_get $seq, undef, 1, my $value;
		427
		428
91	=head2 SUPPORT FUNCTIONS	429	=head2 SUPPORT FUNCTIONS
92		430
93	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	431	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
94		432
95	=over 4	433	=over 4
		434
		435	=item $msg = BDB::strerror [$errno]
		436
		437	Returns the string corresponding to the given errno value. If no argument
		438	is given, use C<$!>.
96		439
97	=item $fileno = BDB::poll_fileno	440	=item $fileno = BDB::poll_fileno
98		441
99	Return the I<request result pipe file descriptor>. This filehandle must be	442	Return the I<request result pipe file descriptor>. This filehandle must be
100	polled for reading by some mechanism outside this module (e.g. Event or	443	polled for reading by some mechanism outside this module (e.g. Event or
…		…
139	interactiveness when perl is not fast enough to process all requests in	482	interactiveness when perl is not fast enough to process all requests in
140	time.	483	time.
141		484
142	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	485	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
143		486
144	Example: Install an Event watcher that automatically calls	487	Example: Install an EV watcher that automatically calls
145	BDB::poll_cb with low priority, to ensure that other parts of the	488	BDB::poll_cb with low priority, to ensure that other parts of the
146	program get the CPU sometimes even under high AIO load.	489	program get the CPU sometimes even under high load.
147		490
148	# try not to spend much more than 0.1s in poll_cb	491	# try not to spend much more than 0.1s in poll_cb
149	BDB::max_poll_time 0.1;	492	BDB::max_poll_time 0.1;
150		493
151	# use a low priority so other tasks have priority	494	my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
152	Event->io (fd => BDB::poll_fileno,
153	poll => 'r', nice => 1,
154	cb => &BDB::poll_cb);
155		495
156	=item BDB::poll_wait	496	=item BDB::poll_wait
157		497
158	If there are any outstanding requests and none of them in the result	498	If there are any outstanding requests and none of them in the result
159	phase, wait till the result filehandle becomes ready for reading (simply	499	phase, wait till the result filehandle becomes ready for reading (simply
…		…
171		511
172	BDB::poll_wait, BDB::poll_cb	512	BDB::poll_wait, BDB::poll_cb
173		513
174	=item BDB::flush	514	=item BDB::flush
175		515
176	Wait till all outstanding AIO requests have been handled.	516	Wait till all outstanding BDB requests have been handled.
177		517
178	Strictly equivalent to:	518	Strictly equivalent to:
179		519
180	BDB::poll_wait, BDB::poll_cb	520	BDB::poll_wait, BDB::poll_cb
181	while BDB::nreqs;	521	while BDB::nreqs;
182		522
		523	=back
		524
183	=head3 CONTROLLING THE NUMBER OF THREADS	525	=head3 CONTROLLING THE NUMBER OF THREADS
184		526
		527	=over 4
		528
185	=item BDB::min_parallel $nthreads	529	=item BDB::min_parallel $nthreads
186		530
187	Set the minimum number of AIO threads to C<$nthreads>. The current	531	Set the minimum number of BDB threads to C<$nthreads>. The current
188	default is C<8>, which means eight asynchronous operations can execute	532	default is C<8>, which means eight asynchronous operations can execute
189	concurrently at any one time (the number of outstanding requests,	533	concurrently at any one time (the number of outstanding requests,
190	however, is unlimited).	534	however, is unlimited).
191		535
192	BDB starts threads only on demand, when an AIO request is queued and	536	BDB starts threads only on demand, when an BDB request is queued and
193	no free thread exists. Please note that queueing up a hundred requests can	537	no free thread exists. Please note that queueing up a hundred requests can
194	create demand for a hundred threads, even if it turns out that everything	538	create demand for a hundred threads, even if it turns out that everything
195	is in the cache and could have been processed faster by a single thread.	539	is in the cache and could have been processed faster by a single thread.
196		540
197	It is recommended to keep the number of threads relatively low, as some	541	It is recommended to keep the number of threads relatively low, as some
…		…
202	Under most circumstances you don't need to call this function, as the	546	Under most circumstances you don't need to call this function, as the
203	module selects a default that is suitable for low to moderate load.	547	module selects a default that is suitable for low to moderate load.
204		548
205	=item BDB::max_parallel $nthreads	549	=item BDB::max_parallel $nthreads
206		550
207	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	551	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
208	specified number of threads are currently running, this function kills	552	specified number of threads are currently running, this function kills
209	them. This function blocks until the limit is reached.	553	them. This function blocks until the limit is reached.
210		554
211	While C<$nthreads> are zero, aio requests get queued but not executed	555	While C<$nthreads> are zero, aio requests get queued but not executed
212	until the number of threads has been increased again.	556	until the number of threads has been increased again.
…		…
315		659
316	=head2 FORK BEHAVIOUR	660	=head2 FORK BEHAVIOUR
317		661
318	This module should do "the right thing" when the process using it forks:	662	This module should do "the right thing" when the process using it forks:
319		663
320	Before the fork, IO::AIO enters a quiescent state where no requests	664	Before the fork, BDB enters a quiescent state where no requests
321	can be added in other threads and no results will be processed. After	665	can be added in other threads and no results will be processed. After
322	the fork the parent simply leaves the quiescent state and continues	666	the fork the parent simply leaves the quiescent state and continues
323	request/result processing, while the child frees the request/result queue	667	request/result processing, while the child frees the request/result queue
324	(so that the requests started before the fork will only be handled in the	668	(so that the requests started before the fork will only be handled in the
325	parent). Threads will be started on demand until the limit set in the	669	parent). Threads will be started on demand until the limit set in the
326	parent process has been reached again.	670	parent process has been reached again.
327		671
328	In short: the parent will, after a short pause, continue as if fork had	672	In short: the parent will, after a short pause, continue as if fork had
329	not been called, while the child will act as if IO::AIO has not been used	673	not been called, while the child will act as if BDB has not been used
330	yet.	674	yet.
		675
		676	Win32 note: there is no fork on win32, and perls emulation of it is too
		677	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		678	yet, switch to a more capable platform.
331		679
332	=head2 MEMORY USAGE	680	=head2 MEMORY USAGE
333		681
334	Per-request usage:	682	Per-request usage:
335		683
…		…
337	bytes of memory. In addition, stat requests need a stat buffer (possibly	685	bytes of memory. In addition, stat requests need a stat buffer (possibly
338	a few hundred bytes), readdir requires a result buffer and so on. Perl	686	a few hundred bytes), readdir requires a result buffer and so on. Perl
339	scalars and other data passed into aio requests will also be locked and	687	scalars and other data passed into aio requests will also be locked and
340	will consume memory till the request has entered the done state.	688	will consume memory till the request has entered the done state.
341		689
342	This is now awfully much, so queuing lots of requests is not usually a	690	This is not awfully much, so queuing lots of requests is not usually a
343	problem.	691	problem.
344		692
345	Per-thread usage:	693	Per-thread usage:
346		694
347	In the execution phase, some aio requests require more memory for	695	In the execution phase, some aio requests require more memory for
348	temporary buffers, and each thread requires a stack and other data	696	temporary buffers, and each thread requires a stack and other data
349	structures (usually around 16k-128k, depending on the OS).	697	structures (usually around 16k-128k, depending on the OS).
350		698
351	=head1 KNOWN BUGS	699	=head1 KNOWN BUGS
352		700
353	Known bugs will be fixed in the next release.	701	Known bugs will be fixed in the next release, except:
		702
		703	If you use a transaction in any request, and the request returns
		704	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		705	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		706	above.
354		707
355	=head1 SEE ALSO	708	=head1 SEE ALSO
356		709
357	L<Coro::AIO>.	710	L<Coro::BDB>, L<IO::AIO>.
358		711
359	=head1 AUTHOR	712	=head1 AUTHOR
360		713
361	Marc Lehmann <schmorp@schmorp.de>	714	Marc Lehmann <schmorp@schmorp.de>
362	http://home.schmorp.de/	715	http://home.schmorp.de/

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Comparing BDB/BDB.pm (file contents): Revision 1.6 by root, Sun Feb 11 22:07:23 2007 UTC vs. Revision 1.26 by root, Tue Dec 11 01:45:16 2007 UTC

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Comparing BDB/BDB.pm (file contents):
Revision 1.6 by root, Sun Feb 11 22:07:23 2007 UTC vs.
Revision 1.26 by root, Tue Dec 11 01:45:16 2007 UTC