[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 1.34 by root, Sun Mar 30 06:17:31 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 result processing with AnyEvent:
		33	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		34	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		35
		36	# automatic result processing with EV:
		37	my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
		38
		39	# with Glib:
		40	add_watch Glib::IO BDB::poll_fileno,
		41	in => sub { BDB::poll_cb; 1 };
		42
		43	# or simply flush manually
		44	BDB::flush;
		45
		46
9	=head1 DESCRIPTION	47	=head1 DESCRIPTION
10		48
11	=head2 EXAMPLE	49	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
		50	The BDB API is very similar to the C API (the translation has been very faithful).
		51
		52	See also the example sections in the document below and possibly the eg/
		53	subdirectory of the BDB distribution. Last not least see the IO::AIO
		54	documentation, as that module uses almost the same asynchronous request
		55	model as this module.
		56
		57	I know this is woefully inadequate documentation. Send a patch!
		58
12		59
13	=head1 REQUEST ANATOMY AND LIFETIME	60	=head1 REQUEST ANATOMY AND LIFETIME
14		61
15	Every request method creates a request. which is a C data structure not	62	Every request method creates a request. which is a C data structure not
16	directly visible to Perl.	63	directly visible to Perl.
…		…
63	use strict 'vars';	110	use strict 'vars';
64		111
65	use base 'Exporter';	112	use base 'Exporter';
66		113
67	BEGIN {	114	BEGIN {
68	our $VERSION = '0.1';	115	our $VERSION = '1.44';
69		116
70	our @BDB_REQ = qw();	117	our @BDB_REQ = qw(
		118	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		119	db_env_memp_sync db_env_memp_trickle
		120	db_open db_close db_compact db_sync db_upgrade
		121	db_put db_get db_pget db_del db_key_range
		122	db_txn_commit db_txn_abort db_txn_finish
		123	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		124	db_sequence_open db_sequence_close
		125	db_sequence_get db_sequence_remove
		126	);
		127	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		128	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	129	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	130	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	131	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	132	max_poll_time max_poll_reqs
		133	);
75		134
76	require XSLoader;	135	require XSLoader;
77	XSLoader::load ("BDB", $VERSION);	136	XSLoader::load ("BDB", $VERSION);
78	}	137	}
79		138
		139	=head2 FILENAMES/DATABASE NAMES
		140
		141	The BDB expects "binary" filenames (octet strings) for pathnames on POSIX
		142	systems, and "unicode" filenames (strings with characters potentially
		143	>255) on Win32 (expecting a Unicode win32 build - win32 is a total mess).
		144
		145	=head2 BERKELEYDB FUNCTIONS
		146
		147	All of these are functions. The create functions simply return a new
		148	object and never block. All the remaining functions take an optional
		149	callback as last argument. If it is missing, then the function will be
		150	executed synchronously. In both cases, C<$!> will reflect the return value
		151	of the function.
		152
		153	BDB functions that cannot block (mostly functions that manipulate
		154	settings) are method calls on the relevant objects, so the rule of thumb
		155	is: if it's a method, it's not blocking, if it's a function, it takes a
		156	callback as last argument.
		157
		158	In the following, C<$int> signifies an integer return value,
		159	C<octetstring> is a "binary string" (i.e. a perl string with no character
		160	indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
		161	integer, C<NV> is a floating point value.
		162
		163	The C<SV *> types are generic perl scalars (for input and output of data
		164	values), and the C<SV *callback> is the optional callback function to call
		165	when the request is completed.
		166
		167	The various C<DB_ENV> etc. arguments are handles return by
		168	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		169	appended C<_ornull> this means they are optional and you can pass C<undef>
		170	for them, resulting a NULL pointer on the C level.
		171
		172	=head3 BDB functions
		173
		174	Functions in the BDB namespace, exported by default:
		175
		176	$env = db_env_create (U32 env_flags = 0)
		177	flags: RPCCLIENT
		178
		179	db_env_open (DB_ENV env, octetstring db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		180	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
		181	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		182	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		183	flags: FORCE
		184	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		185	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		186	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		187	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		188
		189	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		190	flags: XA_CREATE
		191
		192	db_open (DB db, DB_TXN_ornull txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		193	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		194	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		195	flags: DB_NOSYNC
		196	db_upgrade (DB db, octetstring file, U32 flags = 0, SV callback = &PL_sv_undef)
		197	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)
		198	flags: FREELIST_ONLY FREE_SPACE
		199	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		200	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		201	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		202	flags: APPEND NODUPDATA NOOVERWRITE
		203	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		204	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		205	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		206	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		207	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		208	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		209	flags: TXN_NOSYNC TXN_SYNC
		210	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		211
		212	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		213	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		214	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		215	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		216	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		217	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
		218	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		219	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		220
		221	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		222	flags: CREATE EXCL
		223	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		224	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)
		225	flags: TXN_NOSYNC
		226	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		227	flags: TXN_NOSYNC
		228
		229	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		230
		231	This is not actually a Berkeley DB function but a BDB module
		232	extension. The background for this exytension is: It is very annoying to
		233	have to check every single BDB function for error returns and provide a
		234	codepath out of your transaction. While the BDB module still makes this
		235	possible, it contains the following extensions:
		236
		237	When a transaction-protected function returns any operating system
		238	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		239	transaction. This flag is also set by Berkeley DB functions themselves
		240	when an operation fails with LOCK_DEADLOCK, and it causes all further
		241	operations on that transaction (including C<db_txn_commit>) to fail.
		242
		243	The C<db_txn_finish> request will look at this flag, and, if it is set,
		244	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		245	if it isn't set to something else yet). If it isn't set, it will call
		246	C<db_txn_commit> and return the error normally.
		247
		248	How to use this? Easy: just write your transaction normally:
		249
		250	my $txn = $db_env->txn_begin;
		251	db_get $db, $txn, "key", my $data;
		252	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		253	db_txn_finish $txn;
		254	die "transaction failed" if $!;
		255
		256	That is, handle only the expected errors. If something unexpected happens
		257	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		258	requests (db_put in this case) will simply be skipped (they will fail with
		259	LOCK_DEADLOCK) and the transaction will be aborted.
		260
		261	You can use the C<< $txn->failed >> method to check wether a transaction
		262	has failed in this way and abort further processing (excluding
		263	C<db_txn_finish>).
		264
		265	=head3 DB_ENV/database environment methods
		266
		267	Methods available on DB_ENV/$env handles:
		268
		269	DESTROY (DB_ENV_ornull *env)
		270	CODE:
		271	if (env)
		272	env->close (env, 0);
		273
		274	$int = $env->set_data_dir (const char *dir)
		275	$int = $env->set_tmp_dir (const char *dir)
		276	$int = $env->set_lg_dir (const char *dir)
		277	$int = $env->set_shm_key (long shm_key)
		278	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		279	$int = $env->set_flags (U32 flags, int onoff)
		280	$env->set_errfile (FILE *errfile = 0)
		281	$env->set_msgfile (FILE *msgfile = 0)
		282	$int = $env->set_verbose (U32 which, int onoff = 1)
		283	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		284	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		285	$int = $env->set_mp_max_openfd (int maxopenfd);
		286	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		287	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		288	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		289	$int = $env->set_lk_max_lockers (U32 max)
		290	$int = $env->set_lk_max_locks (U32 max)
		291	$int = $env->set_lk_max_objects (U32 max)
		292	$int = $env->set_lg_bsize (U32 max)
		293	$int = $env->set_lg_max (U32 max)
		294	$int = $env->mutex_set_increment (U32 increment)
		295	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		296	$int = $env->mutex_set_max (U32 max)
		297	$int = $env->mutex_set_align (U32 align)
		298
		299	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		300	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		301
		302	=head4 Example:
		303
		304	use AnyEvent;
		305	use BDB;
		306
		307	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		308	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		309
		310	BDB::min_parallel 8;
		311
		312	my $env = db_env_create;
		313
		314	mkdir "bdtest", 0700;
		315	db_env_open
		316	$env,
		317	"bdtest",
		318	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		319	0600;
		320
		321	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		322
		323
		324	=head3 DB/database methods
		325
		326	Methods available on DB/$db handles:
		327
		328	DESTROY (DB_ornull *db)
		329	CODE:
		330	if (db)
		331	{
		332	SV env = (SV )db->app_private;
		333	db->close (db, 0);
		334	SvREFCNT_dec (env);
		335	}
		336
		337	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		338	$int = $db->set_flags (U32 flags)
		339	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		340	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		341	Hash: DUP DUPSORT
		342	Queue: INORDER
		343	Recno: RENUMBER SNAPSHOT
		344
		345	$int = $db->set_encrypt (const char *password, U32 flags)
		346	$int = $db->set_lorder (int lorder)
		347	$int = $db->set_bt_minkey (U32 minkey)
		348	$int = $db->set_re_delim (int delim)
		349	$int = $db->set_re_pad (int re_pad)
		350	$int = $db->set_re_source (char *source)
		351	$int = $db->set_re_len (U32 re_len)
		352	$int = $db->set_h_ffactor (U32 h_ffactor)
		353	$int = $db->set_h_nelem (U32 h_nelem)
		354	$int = $db->set_q_extentsize (U32 extentsize)
		355
		356	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		357	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		358	$seq = $db->sequence (U32 flags = 0)
		359
		360	=head4 Example:
		361
		362	my $db = db_create $env;
		363	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		364
		365	for (1..1000) {
		366	db_put $db, undef, "key $_", "data $_";
		367
		368	db_key_range $db, undef, "key $_", my $keyrange;
		369	my ($lt, $eq, $gt) = @$keyrange;
		370	}
		371
		372	db_del $db, undef, "key $_" for 1..1000;
		373
		374	db_sync $db;
		375
		376
		377	=head3 DB_TXN/transaction methods
		378
		379	Methods available on DB_TXN/$txn handles:
		380
		381	DESTROY (DB_TXN_ornull *txn)
		382	CODE:
		383	if (txn)
		384	txn->abort (txn);
		385
		386	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		387	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		388
		389	$bool = $txn->failed
		390	# see db_txn_finish documentation, above
		391
		392
		393	=head3 DBC/cursor methods
		394
		395	Methods available on DBC/$dbc handles:
		396
		397	DESTROY (DBC_ornull *dbc)
		398	CODE:
		399	if (dbc)
		400	dbc->c_close (dbc);
		401
		402	$int = $cursor->set_priority ($priority = PRIORITY_*)
		403
		404	=head4 Example:
		405
		406	my $c = $db->cursor;
		407
		408	for (;;) {
		409	db_c_get $c, my $key, my $data, BDB::NEXT;
		410	warn "<$!,$key,$data>";
		411	last if $!;
		412	}
		413
		414	db_c_close $c;
		415
		416
		417	=head3 DB_SEQUENCE/sequence methods
		418
		419	Methods available on DB_SEQUENCE/$seq handles:
		420
		421	DESTROY (DB_SEQUENCE_ornull *seq)
		422	CODE:
		423	if (seq)
		424	seq->close (seq, 0);
		425
		426	$int = $seq->initial_value (db_seq_t value)
		427	$int = $seq->set_cachesize (U32 size)
		428	$int = $seq->set_flags (U32 flags)
		429	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		430	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		431
		432	=head4 Example:
		433
		434	my $seq = $db->sequence;
		435
		436	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		437	db_sequence_get $seq, undef, 1, my $value;
		438
		439
80	=head2 SUPPORT FUNCTIONS	440	=head2 SUPPORT FUNCTIONS
81		441
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	442	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		443
84	=over 4	444	=over 4
		445
		446	=item $msg = BDB::strerror [$errno]
		447
		448	Returns the string corresponding to the given errno value. If no argument
		449	is given, use C<$!>.
		450
		451	Note that the BDB module also patches the C<$!> variable directly, so you
		452	should be able to get a bdb error string by simply stringifying C<$!>.
85		453
86	=item $fileno = BDB::poll_fileno	454	=item $fileno = BDB::poll_fileno
87		455
88	Return the I<request result pipe file descriptor>. This filehandle must be	456	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	457	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	496	interactiveness when perl is not fast enough to process all requests in
129	time.	497	time.
130		498
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	499	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		500
133	Example: Install an Event watcher that automatically calls	501	Example: Install an EV watcher that automatically calls
134	BDB::poll_cb with low priority, to ensure that other parts of the	502	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	503	program get the CPU sometimes even under high load.
136		504
137	# try not to spend much more than 0.1s in poll_cb	505	# try not to spend much more than 0.1s in poll_cb
138	BDB::max_poll_time 0.1;	506	BDB::max_poll_time 0.1;
139		507
140	# use a low priority so other tasks have priority	508	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		509
145	=item BDB::poll_wait	510	=item BDB::poll_wait
146		511
147	If there are any outstanding requests and none of them in the result	512	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	513	phase, wait till the result filehandle becomes ready for reading (simply
…		…
160		525
161	BDB::poll_wait, BDB::poll_cb	526	BDB::poll_wait, BDB::poll_cb
162		527
163	=item BDB::flush	528	=item BDB::flush
164		529
165	Wait till all outstanding AIO requests have been handled.	530	Wait till all outstanding BDB requests have been handled.
166		531
167	Strictly equivalent to:	532	Strictly equivalent to:
168		533
169	BDB::poll_wait, BDB::poll_cb	534	BDB::poll_wait, BDB::poll_cb
170	while BDB::nreqs;	535	while BDB::nreqs;
171		536
		537	=back
		538
172	=head3 CONTROLLING THE NUMBER OF THREADS	539	=head3 CONTROLLING THE NUMBER OF THREADS
173		540
		541	=over 4
		542
174	=item BDB::min_parallel $nthreads	543	=item BDB::min_parallel $nthreads
175		544
176	Set the minimum number of AIO threads to C<$nthreads>. The current	545	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	546	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	547	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	548	however, is unlimited).
180		549
181	BDB starts threads only on demand, when an AIO request is queued and	550	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	551	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	552	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.	553	is in the cache and could have been processed faster by a single thread.
185		554
186	It is recommended to keep the number of threads relatively low, as some	555	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	560	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.	561	module selects a default that is suitable for low to moderate load.
193		562
194	=item BDB::max_parallel $nthreads	563	=item BDB::max_parallel $nthreads
195		564
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	565	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	566	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	567	them. This function blocks until the limit is reached.
199		568
200	While C<$nthreads> are zero, aio requests get queued but not executed	569	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	570	until the number of threads has been increased again.
…		…
236		605
237	You can still queue as many requests as you want. Therefore,	606	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	607	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).	608	as a stop gap to shield against fatal memory overflow (with large values).
240		609
		610	=item BDB::set_sync_prepare $cb
		611
		612	Sets a callback that is called whenever a request is created without an
		613	explicit callback. It has to return two code references. The first is used
		614	as the request callback, and the second is called to wait until the first
		615	callback has been called. The default implementation works like this:
		616
		617	sub {
		618	my $status;
		619	(
		620	sub { $status = $! },
		621	sub { BDB::poll while !defined $status; $! = $status },
		622	)
		623	}
		624
		625	=back
		626
241	=head3 STATISTICAL INFORMATION	627	=head3 STATISTICAL INFORMATION
		628
		629	=over 4
242		630
243	=item BDB::nreqs	631	=item BDB::nreqs
244		632
245	Returns the number of requests currently in the ready, execute or pending	633	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).	634	states (i.e. for which their callback has not been invoked yet).
…		…
262		650
263	=back	651	=back
264		652
265	=cut	653	=cut
266		654
		655	set_sync_prepare {
		656	my $status;
		657	(
		658	sub {
		659	$status = $!;
		660	},
		661	sub {
		662	BDB::poll while !defined $status;
		663	$! = $status;
		664	},
		665	)
		666	};
		667
267	min_parallel 8;	668	min_parallel 8;
268		669
269	END { flush }	670	END { flush }
270		671
271	1;	672	1;
272		673
273	=head2 FORK BEHAVIOUR	674	=head2 FORK BEHAVIOUR
274		675
275	This module should do "the right thing" when the process using it forks:	676	This module should do "the right thing" when the process using it forks:
276		677
277	Before the fork, IO::AIO enters a quiescent state where no requests	678	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	679	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	680	the fork the parent simply leaves the quiescent state and continues
280	request/result processing, while the child frees the request/result queue	681	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	682	(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	683	parent). Threads will be started on demand until the limit set in the
283	parent process has been reached again.	684	parent process has been reached again.
284		685
285	In short: the parent will, after a short pause, continue as if fork had	686	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	687	not been called, while the child will act as if BDB has not been used
287	yet.	688	yet.
		689
		690	Win32 note: there is no fork on win32, and perls emulation of it is too
		691	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		692	yet, switch to a more capable platform.
288		693
289	=head2 MEMORY USAGE	694	=head2 MEMORY USAGE
290		695
291	Per-request usage:	696	Per-request usage:
292		697
…		…
294	bytes of memory. In addition, stat requests need a stat buffer (possibly	699	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	700	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	701	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.	702	will consume memory till the request has entered the done state.
298		703
299	This is now awfully much, so queuing lots of requests is not usually a	704	This is not awfully much, so queuing lots of requests is not usually a
300	problem.	705	problem.
301		706
302	Per-thread usage:	707	Per-thread usage:
303		708
304	In the execution phase, some aio requests require more memory for	709	In the execution phase, some aio requests require more memory for
305	temporary buffers, and each thread requires a stack and other data	710	temporary buffers, and each thread requires a stack and other data
306	structures (usually around 16k-128k, depending on the OS).	711	structures (usually around 16k-128k, depending on the OS).
307		712
308	=head1 KNOWN BUGS	713	=head1 KNOWN BUGS
309		714
310	Known bugs will be fixed in the next release.	715	Known bugs will be fixed in the next release, except:
		716
		717	If you use a transaction in any request, and the request returns
		718	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		719	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		720	above.
311		721
312	=head1 SEE ALSO	722	=head1 SEE ALSO
313		723
314	L<Coro::AIO>.	724	L<Coro::BDB>, L<IO::AIO>.
315		725
316	=head1 AUTHOR	726	=head1 AUTHOR
317		727
318	Marc Lehmann <schmorp@schmorp.de>	728	Marc Lehmann <schmorp@schmorp.de>
319	http://home.schmorp.de/	729	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 1.34 by root, Sun Mar 30 06:17:31 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 1.34 by root, Sun Mar 30 06:17:31 2008 UTC