[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 1.70 by root, Thu Jan 18 16:45:27 2018 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 integration with AnyEvent:
		33	use AnyEvent::BDB;
		34
		35	# automatic result processing with EV:
		36	my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
		37
		38	# with Glib:
		39	add_watch Glib::IO BDB::poll_fileno,
		40	in => sub { BDB::poll_cb; 1 };
		41
		42	# or simply flush manually
		43	BDB::flush;
		44
		45
9	=head1 DESCRIPTION	46	=head1 DESCRIPTION
10		47
11	=head2 EXAMPLE	48	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
		49	The BDB API is very similar to the C API (the translation has been very faithful).
		50
		51	See also the example sections in the document below and possibly the eg/
		52	subdirectory of the BDB distribution. Last not least see the IO::AIO
		53	documentation, as that module uses almost the same asynchronous request
		54	model as this module.
		55
		56	I know this is woefully inadequate documentation. Send a patch!
		57
12		58
13	=head1 REQUEST ANATOMY AND LIFETIME	59	=head1 REQUEST ANATOMY AND LIFETIME
14		60
15	Every request method creates a request. which is a C data structure not	61	Every request method creates a request. which is a C data structure not
16	directly visible to Perl.	62	directly visible to Perl.
…		…
57		103
58	=cut	104	=cut
59		105
60	package BDB;	106	package BDB;
61		107
62	no warnings;	108	use common::sense;
63	use strict 'vars';
64		109
65	use base 'Exporter';	110	use base 'Exporter';
66		111
		112	our $VERSION;
		113
67	BEGIN {	114	BEGIN {
68	our $VERSION = '0.1';	115	$VERSION = '1.92';
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 db_env_dbrename db_env_dbremove
		120	db_env_log_archive db_env_lsn_reset db_env_fileid_reset
		121	db_open db_close db_compact db_sync db_verify db_upgrade
		122	db_put db_exists db_get db_pget db_del db_key_range
		123	db_txn_commit db_txn_abort db_txn_finish
		124	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		125	db_sequence_open db_sequence_close
		126	db_sequence_get db_sequence_remove
		127	);
		128	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		129	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	130	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	131	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	132	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	133	max_poll_time max_poll_reqs
		134	);
75		135
76	require XSLoader;	136	require XSLoader;
77	XSLoader::load ("BDB", $VERSION);	137	XSLoader::load ("BDB", $VERSION);
78	}	138	}
79		139
		140	=head1 BERKELEYDB FUNCTIONS
		141
		142	All of these are functions. The create functions simply return a new
		143	object and never block. All the remaining functions take an optional
		144	callback as last argument. If it is missing, then the function will be
		145	executed synchronously. In both cases, C<$!> will reflect the return value
		146	of the function.
		147
		148	BDB functions that cannot block (mostly functions that manipulate
		149	settings) are method calls on the relevant objects, so the rule of thumb
		150	is: if it's a method, it's not blocking, if it's a function, it takes a
		151	callback as last argument.
		152
		153	In the following, C<$int> signifies an integer return value,
		154	C<bdb_filename> is a "filename" (octets on unix, madness on windows),
		155	C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
		156	floating point value.
		157
		158	Most C<SV *> types are generic perl scalars (for input and output of data
		159	values).
		160
		161	The various C<DB_ENV> etc. arguments are handles return by
		162	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		163	appended C<_ornull> this means they are optional and you can pass C<undef>
		164	for them, resulting a NULL pointer on the C level.
		165
		166	The C<SV *callback> is the optional callback function to call when the
		167	request is completed. This last callback argument is special: the callback
		168	is simply the last argument passed. If there are "optional" arguments
		169	before the callback they can be left out. The callback itself can be left
		170	out or specified as C<undef>, in which case the function will be executed
		171	synchronously.
		172
		173	For example, C<db_env_txn_checkpoint> usually is called with all integer
		174	arguments zero. These can be left out, so all of these specify a call
		175	to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
		176	callback to be called:
		177
		178	db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
		179	db_env_txn_checkpoint $db_env, 0, 0, sub { };
		180	db_env_txn_checkpoint $db_env, sub { };
		181
		182	While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
		183	executed synchronously:
		184
		185	db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
		186	db_env_txn_checkpoint $db_env, 0, 0, 0;
		187	db_env_txn_checkpoint $db_env, 0;
		188
		189	=head2 BDB functions
		190
		191	Functions in the BDB namespace, exported by default:
		192
		193	$env = db_env_create (U32 env_flags = 0)
		194	flags: RPCCLIENT
		195
		196	db_env_open (DB_ENV env, bdb_filename db_home, U32 open_flags, int mode, SV callback = 0)
		197	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
		198	db_env_close (DB_ENV env, U32 flags = 0, SV callback = 0)
		199	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = 0)
		200	flags: FORCE
		201	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = 0)
		202	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		203	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = 0)
		204	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = 0)
		205	db_env_dbremove (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = 0)
		206	db_env_dbrename (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = 0)
		207	db_env_log_archive (DB_ENV env, SV listp, U32 flags = 0, SV *callback = 0)
		208	db_env_lsn_reset (DB_ENV env, bdb_filename db, U32 flags = 0, SV callback = 0)
		209	db_env_fileid_reset (DB_ENV env, bdb_filename db, U32 flags = 0, SV callback = 0)
		210
		211	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		212	flags: XA_CREATE
		213
		214	db_open (DB db, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = 0)
		215	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		216	db_close (DB db, U32 flags = 0, SV callback = 0)
		217	flags: DB_NOSYNC
		218	db_verify (DB db, bdb_filename file, bdb_filename database = 0, SV dummy = 0, U32 flags = 0, SV *callback = 0)
		219	db_upgrade (DB db, bdb_filename file, U32 flags = 0, SV callback = 0)
		220	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 = 0)
		221	flags: FREELIST_ONLY FREE_SPACE
		222	db_sync (DB db, U32 flags = 0, SV callback = 0)
		223	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = 0)
		224	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = 0)
		225	flags: APPEND NODUPDATA NOOVERWRITE
		226	db_exists (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = 0) (v4.6)
		227	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = 0)
		228	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		229	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = 0)
		230	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		231	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = 0)
		232	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = 0)
		233	flags: TXN_NOSYNC TXN_SYNC
		234	db_txn_abort (DB_TXN txn, SV callback = 0)
		235
		236	db_c_close (DBC dbc, SV callback = 0)
		237	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = 0)
		238	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = 0)
		239	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		240	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = 0)
		241	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
		242	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = 0)
		243	db_c_del (DBC dbc, U32 flags = 0, SV callback = 0)
		244
		245	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = 0)
		246	flags: CREATE EXCL
		247	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = 0)
		248	db_sequence_get (DB_SEQUENCE seq, DB_TXN_ornull txnid, int delta, SV seq_value, U32 flags = DB_TXN_NOSYNC, SV callback = 0)
		249	flags: TXN_NOSYNC
		250	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = 0)
		251	flags: TXN_NOSYNC
		252
		253	=head3 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = 0)
		254
		255	This is not actually a Berkeley DB function but a BDB module
		256	extension. The background for this exytension is: It is very annoying to
		257	have to check every single BDB function for error returns and provide a
		258	codepath out of your transaction. While the BDB module still makes this
		259	possible, it contains the following extensions:
		260
		261	When a transaction-protected function returns any operating system
		262	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		263	transaction. This flag is also set by Berkeley DB functions themselves
		264	when an operation fails with LOCK_DEADLOCK, and it causes all further
		265	operations on that transaction (including C<db_txn_commit>) to fail.
		266
		267	The C<db_txn_finish> request will look at this flag, and, if it is set,
		268	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		269	if it isn't set to something else yet). If it isn't set, it will call
		270	C<db_txn_commit> and return the error normally.
		271
		272	How to use this? Easy: just write your transaction normally:
		273
		274	my $txn = $db_env->txn_begin;
		275	db_get $db, $txn, "key", my $data;
		276	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		277	db_txn_finish $txn;
		278	die "transaction failed" if $!;
		279
		280	That is, handle only the expected errors. If something unexpected happens
		281	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		282	requests (db_put in this case) will simply be skipped (they will fail with
		283	LOCK_DEADLOCK) and the transaction will be aborted.
		284
		285	You can use the C<< $txn->failed >> method to check wether a transaction
		286	has failed in this way and abort further processing (excluding
		287	C<db_txn_finish>).
		288
		289
		290	=head2 DB_ENV/database environment methods
		291
		292	Methods available on DB_ENV/$env handles:
		293
		294	DESTROY (DB_ENV_ornull *env)
		295	CODE:
		296	if (env)
		297	env->close (env, 0);
		298
		299	$int = $env->set_data_dir (const char *dir)
		300	$int = $env->set_tmp_dir (const char *dir)
		301	$int = $env->set_lg_dir (const char *dir)
		302	$int = $env->set_shm_key (long shm_key)
		303	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		304	$int = $env->set_flags (U32 flags, int onoff = 1)
		305	$int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
		306	$int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
		307	$env->set_errfile (FILE *errfile = 0)
		308	$env->set_msgfile (FILE *msgfile = 0)
		309	$int = $env->set_verbose (U32 which, int onoff = 1)
		310	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		311	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		312	$int = $env->set_mp_max_openfd (int maxopenfd);
		313	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		314	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		315	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		316	$int = $env->set_lk_max_lockers (U32 max)
		317	$int = $env->set_lk_max_locks (U32 max)
		318	$int = $env->set_lk_max_objects (U32 max)
		319	$int = $env->set_lg_bsize (U32 max)
		320	$int = $env->set_lg_max (U32 max)
		321	$int = $env->mutex_set_increment (U32 increment)
		322	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		323	$int = $env->mutex_set_max (U32 max)
		324	$int = $env->mutex_set_align (U32 align)
		325
		326	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		327	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		328	$txn = $env->cdsgroup_begin; (v4.5)
		329
		330	=head3 Example:
		331
		332	use AnyEvent;
		333	use BDB;
		334
		335	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		336	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		337
		338	BDB::min_parallel 8;
		339
		340	my $env = db_env_create;
		341
		342	mkdir "bdtest", 0700;
		343	db_env_open
		344	$env,
		345	"bdtest",
		346	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		347	0600;
		348
		349	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		350
		351
		352	=head2 DB/database methods
		353
		354	Methods available on DB/$db handles:
		355
		356	DESTROY (DB_ornull *db)
		357	CODE:
		358	if (db)
		359	{
		360	SV env = (SV )db->app_private;
		361	db->close (db, 0);
		362	SvREFCNT_dec (env);
		363	}
		364
		365	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		366	$int = $db->set_flags (U32 flags)
		367	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		368	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		369	Hash: DUP DUPSORT
		370	Queue: INORDER
		371	Recno: RENUMBER SNAPSHOT
		372
		373	$int = $db->set_encrypt (const char *password, U32 flags)
		374	$int = $db->set_lorder (int lorder)
		375	$int = $db->set_bt_minkey (U32 minkey)
		376	$int = $db->set_re_delim (int delim)
		377	$int = $db->set_re_pad (int re_pad)
		378	$int = $db->set_re_source (char *source)
		379	$int = $db->set_re_len (U32 re_len)
		380	$int = $db->set_h_ffactor (U32 h_ffactor)
		381	$int = $db->set_h_nelem (U32 h_nelem)
		382	$int = $db->set_q_extentsize (U32 extentsize)
		383
		384	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		385	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		386	$seq = $db->sequence (U32 flags = 0)
		387
		388	=head3 Example:
		389
		390	my $db = db_create $env;
		391	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		392
		393	for (1..1000) {
		394	db_put $db, undef, "key $_", "data $_";
		395
		396	db_key_range $db, undef, "key $_", my $keyrange;
		397	my ($lt, $eq, $gt) = @$keyrange;
		398	}
		399
		400	db_del $db, undef, "key $_" for 1..1000;
		401
		402	db_sync $db;
		403
		404
		405	=head2 DB_TXN/transaction methods
		406
		407	Methods available on DB_TXN/$txn handles:
		408
		409	DESTROY (DB_TXN_ornull *txn)
		410	CODE:
		411	if (txn)
		412	txn->abort (txn);
		413
		414	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		415	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		416
		417	$bool = $txn->failed
		418	# see db_txn_finish documentation, above
		419
		420
		421	=head2 DBC/cursor methods
		422
		423	Methods available on DBC/$dbc handles:
		424
		425	DESTROY (DBC_ornull *dbc)
		426	CODE:
		427	if (dbc)
		428	dbc->c_close (dbc);
		429
		430	$int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
		431
		432	=head3 Example:
		433
		434	my $c = $db->cursor;
		435
		436	for (;;) {
		437	db_c_get $c, my $key, my $data, BDB::NEXT;
		438	warn "<$!,$key,$data>";
		439	last if $!;
		440	}
		441
		442	db_c_close $c;
		443
		444
		445	=head2 DB_SEQUENCE/sequence methods
		446
		447	Methods available on DB_SEQUENCE/$seq handles:
		448
		449	DESTROY (DB_SEQUENCE_ornull *seq)
		450	CODE:
		451	if (seq)
		452	seq->close (seq, 0);
		453
		454	$int = $seq->initial_value (db_seq_t value)
		455	$int = $seq->set_cachesize (U32 size)
		456	$int = $seq->set_flags (U32 flags)
		457	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		458	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		459
		460	=head3 Example:
		461
		462	my $seq = $db->sequence;
		463
		464	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		465	db_sequence_get $seq, undef, 1, my $value;
		466
		467
80	=head2 SUPPORT FUNCTIONS	468	=head1 SUPPORT FUNCTIONS
81		469
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	470	=head2 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		471
84	=over 4	472	=over 4
		473
		474	=item $msg = BDB::strerror [$errno]
		475
		476	Returns the string corresponding to the given errno value. If no argument
		477	is given, use C<$!>.
		478
		479	Note that the BDB module also patches the C<$!> variable directly, so you
		480	should be able to get a bdb error string by simply stringifying C<$!>.
85		481
86	=item $fileno = BDB::poll_fileno	482	=item $fileno = BDB::poll_fileno
87		483
88	Return the I<request result pipe file descriptor>. This filehandle must be	484	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	485	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	524	interactiveness when perl is not fast enough to process all requests in
129	time.	525	time.
130		526
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	527	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		528
133	Example: Install an Event watcher that automatically calls	529	Example: Install an EV watcher that automatically calls
134	BDB::poll_cb with low priority, to ensure that other parts of the	530	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	531	program get the CPU sometimes even under high load.
136		532
137	# try not to spend much more than 0.1s in poll_cb	533	# try not to spend much more than 0.1s in poll_cb
138	BDB::max_poll_time 0.1;	534	BDB::max_poll_time 0.1;
139		535
140	# use a low priority so other tasks have priority	536	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		537
145	=item BDB::poll_wait	538	=item BDB::poll_wait
146		539
147	If there are any outstanding requests and none of them in the result	540	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	541	phase, wait till the result filehandle becomes ready for reading (simply
…		…
160		553
161	BDB::poll_wait, BDB::poll_cb	554	BDB::poll_wait, BDB::poll_cb
162		555
163	=item BDB::flush	556	=item BDB::flush
164		557
165	Wait till all outstanding AIO requests have been handled.	558	Wait till all outstanding BDB requests have been handled.
166		559
167	Strictly equivalent to:	560	Strictly equivalent to:
168		561
169	BDB::poll_wait, BDB::poll_cb	562	BDB::poll_wait, BDB::poll_cb
170	while BDB::nreqs;	563	while BDB::nreqs;
171		564
		565	=back
		566
		567	=head2 VERSION CHECKING
		568
		569	BerkeleyDB comes in various versions, many of them have minor
		570	incompatibilities. This means that traditional "at least version x.x"
		571	checks are often not sufficient.
		572
		573	Example: set the log_autoremove option in a way compatible with <v4.7 and
		574	v4.7. Note the use of & on the constants to avoid triggering a compiletime
		575	bug when the symbol isn't available.
		576
		577	$DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
		578	$DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
		579
		580	=over 4
		581
		582	=item BDB::VERSION
		583
		584	The C<BDB::VERSION> function, when called without arguments, returns the
		585	Berkeley DB version as a v-string (usually with 3 components). You should
		586	use C<lt> and C<ge> operators exclusively to make comparisons.
		587
		588	Example: check for at least version 4.7.
		589
		590	BDB::VERSION ge v4.7 or die;
		591
		592	=item BDB::VERSION min-version
		593
		594	Returns true if the BDB version is at least the given version (specified
		595	as a v-string), false otherwise.
		596
		597	Example: check for at least version 4.5.
		598
		599	BDB::VERSION v4.7 or die;
		600
		601	=item BDB::VERSION min-version, max-version
		602
		603	Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
		604	and less then C<max-version>.
		605
		606	Example: check wether version is strictly less then v4.7.
		607
		608	BDB::VERSION v0, v4.7
		609	or die "version 4.7 is not yet supported";
		610
		611	=back
		612
		613	=cut
		614
		615	sub VERSION {
		616	# I was dumb enough to override the VERSION method here, so let's try
		617	# to fix it up.
		618
		619	if ($_[0] eq __PACKAGE__) {
		620	$VERSION
		621	} else {
		622	if (@_ > 0) {
		623	return undef if VERSION_v lt $_[0];
		624	if (@_ > 1) {
		625	return undef if VERSION_v ge $_[1];
		626	}
		627	}
		628
		629	VERSION_v
		630	}
		631	}
		632
172	=head3 CONTROLLING THE NUMBER OF THREADS	633	=head2 CONTROLLING THE NUMBER OF THREADS
		634
		635	=over 4
173		636
174	=item BDB::min_parallel $nthreads	637	=item BDB::min_parallel $nthreads
175		638
176	Set the minimum number of AIO threads to C<$nthreads>. The current	639	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	640	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	641	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	642	however, is unlimited).
180		643
181	BDB starts threads only on demand, when an AIO request is queued and	644	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	645	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	646	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.	647	is in the cache and could have been processed faster by a single thread.
185		648
186	It is recommended to keep the number of threads relatively low, as some	649	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	654	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.	655	module selects a default that is suitable for low to moderate load.
193		656
194	=item BDB::max_parallel $nthreads	657	=item BDB::max_parallel $nthreads
195		658
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	659	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	660	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	661	them. This function blocks until the limit is reached.
199		662
200	While C<$nthreads> are zero, aio requests get queued but not executed	663	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	664	until the number of threads has been increased again.
…		…
236		699
237	You can still queue as many requests as you want. Therefore,	700	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	701	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).	702	as a stop gap to shield against fatal memory overflow (with large values).
240		703
		704	=item $old_cb = BDB::set_sync_prepare $cb
		705
		706	Sets a callback that is called whenever a request is created without an
		707	explicit callback. It has to return two code references. The first is used
		708	as the request callback (it should save the return status), and the second
		709	is called to wait until the first callback has been called (it must set
		710	C<$!> to the return status).
		711
		712	This mechanism can be used to include BDB into other event mechanisms,
		713	such as L<Coro::BDB>.
		714
		715	To allow other, callback-based, events to be executed while callback-less
		716	ones are run, you could use this sync prepare function:
		717
		718	sub {
		719	my $status;
		720	(
		721	sub { $status = $! },
		722	sub { BDB::poll while !defined $status; $! = $status },
		723	)
		724	}
		725
		726	It works by polling for results till the request has finished and then
		727	sets C<$!> to the return value. This means that if you don't use a
		728	callback, BDB would simply fall back to synchronous operations.
		729
		730	By default, or if the sync prepare function is set to C<undef>, is to
		731	execute callback-less BDB requests in the foreground thread, setting C<$!>
		732	to the return value, without polling for other events.
		733
		734	=back
		735
241	=head3 STATISTICAL INFORMATION	736	=head2 STATISTICAL INFORMATION
		737
		738	=over 4
242		739
243	=item BDB::nreqs	740	=item BDB::nreqs
244		741
245	Returns the number of requests currently in the ready, execute or pending	742	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).	743	states (i.e. for which their callback has not been invoked yet).
…		…
262		759
263	=back	760	=back
264		761
265	=cut	762	=cut
266		763
		764	set_sync_prepare (undef);
		765
267	min_parallel 8;	766	min_parallel 8;
268		767
269	END { flush }	768	END { flush }
270		769
271	1;	770	1;
272		771
		772	=head1 COMMON PITFALLS
		773
		774	=head2 Unexpected Crashes
		775
		776	Remember that, by default, BDB will execute requests in parallel, in
		777	somewhat random order. That means that it is easy to run a C<db_get>
		778	request on the same database as a concurrent C<db_close> request, leading
		779	to a crash, silent data corruption, eventually the next world war on
		780	terrorism.
		781
		782	If you only ever use foreground requests (without a callback), this will
		783	not be an issue (unless you use threads).
		784
		785	=head2 Unexpected Freezes or Deadlocks
		786
		787	Remember that, by default, BDB will execute requests in parallel, which
		788	easily leads to deadlocks (even concurrent put's on the same database can
		789	deadlock).
		790
		791	You either need to run deadlock detection (and handle the resulting
		792	errors), or make sure only one process ever updates the database, ine one
		793	thread, e.g. by using only foreground requests (without a callback).
		794
273	=head2 FORK BEHAVIOUR	795	=head1 FORK BEHAVIOUR
274		796
275	This module should do "the right thing" when the process using it forks:	797	This module should do "the right thing" when the process using it forks:
276		798
277	Before the fork, IO::AIO enters a quiescent state where no requests	799	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	800	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	801	the fork the parent simply leaves the quiescent state and continues
280	request/result processing, while the child frees the request/result queue	802	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	803	(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	804	parent). Threads will be started on demand until the limit set in the
283	parent process has been reached again.	805	parent process has been reached again.
284		806
285	In short: the parent will, after a short pause, continue as if fork had	807	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	808	not been called, while the child will act as if BDB has not been used
287	yet.	809	yet.
288		810
		811	Win32 note: there is no fork on win32, and perls emulation of it is too
		812	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		813	yet, switch to a more capable platform.
		814
289	=head2 MEMORY USAGE	815	=head1 MEMORY USAGE
290		816
291	Per-request usage:	817	Per-request usage:
292		818
293	Each aio request uses - depending on your architecture - around 100-200	819	Each aio request uses - depending on your architecture - around 100-200
294	bytes of memory. In addition, stat requests need a stat buffer (possibly	820	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	821	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	822	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.	823	will consume memory till the request has entered the done state.
298		824
299	This is now awfully much, so queuing lots of requests is not usually a	825	This is not awfully much, so queuing lots of requests is not usually a
300	problem.	826	problem.
301		827
302	Per-thread usage:	828	Per-thread usage:
303		829
304	In the execution phase, some aio requests require more memory for	830	In the execution phase, some aio requests require more memory for
305	temporary buffers, and each thread requires a stack and other data	831	temporary buffers, and each thread requires a stack and other data
306	structures (usually around 16k-128k, depending on the OS).	832	structures (usually around 16k-128k, depending on the OS).
307		833
		834	=head1 WIN32 FILENAMES/DATABASE NAME MESS
		835
		836	Perl on Win32 supports only ASCII filenames (the reason is that it abuses
		837	an internal flag to store wether a filename is Unicode or ANSI, but that
		838	flag is used for somethign else in the perl core, so there is no way to
		839	detect wether a filename is ANSI or Unicode-encoded). The BDB module
		840	tries to work around this issue by assuming that the filename is an ANSI
		841	filename and BDB was built for unicode support.
		842
308	=head1 KNOWN BUGS	843	=head1 KNOWN BUGS
309		844
310	Known bugs will be fixed in the next release.	845	Known bugs will be fixed in the next release, except:
		846
		847	If you use a transaction in any request, and the request returns
		848	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		849	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		850	above.
311		851
312	=head1 SEE ALSO	852	=head1 SEE ALSO
313		853
314	L<Coro::AIO>.	854	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		855	syntax), L<IO::AIO> (nice to have).
315		856
316	=head1 AUTHOR	857	=head1 AUTHOR
317		858
318	Marc Lehmann <schmorp@schmorp.de>	859	Marc Lehmann <schmorp@schmorp.de>
319	http://home.schmorp.de/	860	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 1.70 by root, Thu Jan 18 16:45:27 2018 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 1.70 by root, Thu Jan 18 16:45:27 2018 UTC