PApp-SQL/SQL.pm

=head1 NAME

PApp::SQL - absolutely easy yet fast and powerful sql access.

=head1 SYNOPSIS

 use PApp::SQL;

 my $st = sql_exec $DBH, "select ... where a = ?", $a;

 local $DBH = <database handle>;
 my $st = sql_exec \my($bind_a, $bind_b), "select a,b ...";
 my $st = sql_insertid
             sql_exec "insert into ... values (?, ?)", $v1, $v2;
 my $a = sql_fetch "select a from ...";
 sql_fetch \my($a, $b), "select a,b ...";

 sql_exists "table where name like 'a%'"
    or die "a* required but not existent";

 my $db = new PApp::SQL::Database "", "DBI:mysql:test", "user", "pass";
 local $PApp::SQL::DBH = $db->checked_dbh; # does 'ping'

 sql_exec $db->dbh, "select ...";

=head1 DESCRIPTION

This module provides you with easy-to-use functions to execute sql
commands (using DBI). Despite being easy to use, they are also quite
efficient and allow you to write faster programs in less lines of code. It
should work with anything from perl-5.004_01 onwards, but I only support
5.005+. UTF8 handling (the C<sql_u*> family of functions) will only be
effective with perl version 5.006 and beyond.

If the descriptions here seem terse or if you always wanted to know
what PApp is then have a look at the PApp module which uses this module
extensively but also provides you with a lot more gimmicks to play around
with to help you create cool applications ;)

=cut

package PApp::SQL;

use DBI ();

BEGIN {
   use base qw(Exporter DynaLoader);

   $VERSION = 0.13;
   @EXPORT = qw(
         sql_exec  sql_fetch  sql_fetchall  sql_exists sql_insertid $sql_exec
         sql_uexec sql_ufetch sql_ufetchall sql_uexists
   );
   @EXPORT_OK = qw(
         connect_cached
   );

   bootstrap PApp::SQL $VERSION;
}

our $sql_exec;  # last result of sql_exec's execute call
our $DBH;       # the default database handle
our $Database;  # the current SQL::Database object, if applicable

our %dbcache;

=head2 GLOBAL VARIABLES

=over 4

=item $sql_exec

Since the C<sql_exec> family of functions return a statement handle there
must eb another way to test the return value of the C<execute> call. This
global variable contains the result of the most recent call to C<execute>
done by this module.

=item $PApp::SQL::DBH

The default database handle used by this module if no C<$DBH> was
specified as argument and no C<$DBH> is found in the current package. See
C<sql_exec> for a discussion.

=item $PApp::SQL::Database

The current default C<PApp::SQL::Database>-object. Future versions might
automatically fall back on this database and create database handles from
it if neccessary. At the moment this is not used by this module but might
be nice as a placeholder for the database object that corresponds to
$PApp::SQL::DBH.

=back

=head2 FUNCTIONS

=over 4

=item $dbh = connect_cached $id, $dsn, $user, $pass, $flags, $connect

(not exported by by default)

Connect to the database given by C<($dsn,$user,$pass)>, while using the
flags from C<$flags>. These are just the same arguments as given to
C<DBI->connect>.

The database handle will be cached under the unique id
C<$id|$dsn|$user|$pass>. If the same id is requested later, the
cached handle will be checked (using ping), and the connection will
be re-established if necessary (be sure to prefix your application or
module name to the id to make it "more" unique. Things like __PACKAGE__ .
__LINE__ work fine as well).

The reason C<$id> is necessary is that you might specify special connect
arguments or special flags, or you might want to configure your $DBH
differently than maybe other applications requesting the same database
connection. If none of this is becessary for your application you can
leave $id empty (i.e. "").

If specified, C<$connect> is a callback (e.g. a coderef) that will be
called each time a new connection is being established, with the new
C<$dbh> as first argument.

Examples:

 # try your luck opening the papp database without access info
 $dbh = connect_cached __FILE__, "DBI:mysql:papp";

Mysql-specific behaviour: The default setting of
C<mysql_client_found_rows> is TRUE, you can overwrite this, though.

=cut

sub connect_cached {
   my ($id, $dsn, $user, $pass, $flags, $connect) = @_;
   # the following line is duplicated in PApp::SQL::Database::new
   $id = "$id\0$dsn\0$user\0$pass";
   unless ($dbcache{$id} && $dbcache{$id}->ping) {
      # first, nuke our statement cache (sooory ;)
      cachesize cachesize 0;

      # then make mysql behave more standardly by default
      $dsn =~ /^[Dd][Bb][Ii]:mysql:/
         and $dsn !~ /;mysql_client_found_rows/
            and $dsn .= ";mysql_client_found_rows=1";

      # then connect anew
      $dbcache{$id} =
         eval { DBI->connect($dsn, $user, $pass, $flags) }
         || eval { DBI->connect($dsn, $user, $pass, $flags) }
         || die "unable to connect to database $dsn: $DBI::errstr\n";
      $connect->($dbcache{$id}) if $connect;
   }
   $dbcache{$id};
}

=item $sth = sql_exec [dbh,] [bind-vals...,] "sql-statement", [arguments...]

=item $sth = sql_uexec <see sql_exec>

C<sql_exec> is the most important and most-used function in this module.

Runs the given sql command with the given parameters and returns the
statement handle. The command and the statement handle will be cached
(with the database handle and the sql string as key), so prepare will be
called only once for each distinct sql call (please keep in mind that the
returned statement will always be the same, so, if you call C<sql_exec>
with the same dbh and sql-statement twice (e.g. in a subroutine you
called), the statement handle for the first call mustn't be used.

The database handle (the first argument) is optional. If it is missing,
C<sql_exec> first tries to use the variable C<$DBH> in the current (=
calling) package and, if that fails, it tries to use database handle in
C<$PApp::SQL::DBH>, which you can set before calling these functions.

The actual return value from the C<$sth->execute> call is stored in the
package-global (and exported) variable C<$sql_exec>.

If any error occurs C<sql_exec> will throw an exception.

C<sql_uexec> is similar to C<sql_exec> but upgrades all input arguments to
utf8 before calling the C<execute> method.

Examples:

 # easy one
 my $st = sql_exec "select name, id from table where id = ?", $id;
 while (my ($name, $id) = $st->fetchrow_array) { ... };

 # the fastest way to use dbi, using bind_columns
 my $st = sql_exec \my($name, $id),
                   "select name, id from table where id = ?",
                   $id;
 while ($st->fetch) { ...}

 # now use a different dastabase:
 sql_exec $dbh, "update file set name = ?", "oops.txt";


=item sql_fetch <see sql_exec>

=item sql_ufetch <see sql_uexec>

Execute an sql-statement and fetch the first row of results. Depending on
the caller context the row will be returned as a list (array context), or
just the first columns. In table form:

 CONTEXT        RESULT
 void           ()
 scalar         first column
 list           array

C<sql_fetch> is quite efficient in conjunction with bind variables:

 sql_fetch \my($name, $amount),
           "select name, amount from table where id name  = ?",
           "Toytest";

But of course the normal way to call it is simply:

 my($name, $amount) = sql_fetch "select ...", args...

... and it's still quite fast unless you fetch large amounts of data.

C<sql_ufetch> is similar to C<sql_fetch> but upgrades all input values to
utf8 and forces all result values to utf8 (this does I<not> include result
parameters, only return values. Using bind variables in cinjunction with
sql_u* functions results in undefined behaviour).

=item sql_fetchall <see sql_exec>

=item sql_ufetchall <see sql_uexec>

Similarly to C<sql_fetch>, but all result rows will be fetched (this is
of course inefficient for large results!). The context is ignored (only
list context makes sense), but the result still depends on the number of
columns in the result:

 COLUMNS        RESULT
 0              ()
 1              (row1, row2, row3...)
 many           ([row1], [row2], [row3]...)

Examples (all of which are inefficient):

 for (sql_fetchall "select id from table") { ... }

 my @names = sql_fetchall "select name from user";

 for (sql_fetchall "select name, age, place from user") {
    my ($name, $age, $place) = @$_;
 }

C<sql_ufetchall> is similar to C<sql_fetchall> but upgrades all input
values to utf8 and forces all result values to utf8 (see the caveats in
the description of C<sql_ufetch>, though).

=item sql_exists "<table_references> where <where_condition>...", args...

=item sql_uexists <see sql_exists>

Check wether the result of the sql-statement "select xxx from
$first_argument" would be empty or not (that is, imagine the string
"select * from" were prepended to your statement (it isn't)). Should work
with every database but can be quite slow, except on mysql, where this
should be quite fast.

C<sql_uexists> is similar to C<sql_exists> but upgrades all parameters to
utf8.

Examples:

 print "user 7 exists!\n"
    if sql_exists "user where id = ?", 7;
 
 die "duplicate key"
    if sql_exists "user where name = ? and pass = ?", "stefan", "geheim";

=cut

=item $lastid = sql_insertid $sth

Returns the last automatically created key value. It must be executed
directly after executing the insert statement that created it. This is
what is actually returned for various databases. If your database is
missing, please send me an e-mail on how to implement this ;)

 mysql:    first C<AUTO_INCREMENT> column set to NULL
 postgres: C<oid> column (is there a way to get the last SERIAL?)
 sybase:   C<IDENTITY> column of the last insert (slow)
 informix: C<SERIAL> or C<SERIAL8> column of the last insert

Except for sybase, this does not require a server access.

=cut

sub sql_insertid($) {
   my $sth = shift or die "sql_insertid requires a statement handle";
   my $dbh = $sth->{Database};
   my $driver = $dbh->{Driver}{Name};

   $driver eq "mysql"    and return $sth->{mysql_insertid};
   $driver eq "Pg"       and return $sth->{pg_oid_status};
   $driver eq "Sybase"   and return sql_fetch($dbh, 'SELECT @@IDENTITY');
   $driver eq "Informix" and return $sth->{ix_sqlerrd}[1];

   die "sql_insertid does not spport the dbd driver '$driver', please see PApp::SQL::sql_insertid";
}

=item [old-size] = cachesize [new-size]

Returns (and possibly changes) the LRU cache size used by C<sql_exec>. The
default is somewhere around 50 (= the 50 last recently used statements
will be cached). It shouldn't be too large, since a simple linear listed
is used for the cache at the moment (which, for small (<100) cache sizes
is actually quite fast).

The function always returns the cache size in effect I<before> the call,
so, to nuke the cache (for example, when a database connection has died
or you want to garbage collect old database/statement handles), this
construct can be used:

 PApp::SQL::cachesize PApp::SQL::cachesize 0;

=cut

=item reinitialize [not exported]

Clears any internal caches (statement cache, database handle
cache). Should be called after C<fork> and other accidents that invalidate
database handles.

=cut

sub reinitialize {
   cachesize cachesize 0;
   for (values %dbcache) {
      eval { $_->{InactiveDestroy} = 1 };
   }
   undef %dbcache;
}

=back

=cut

reinitialize;

package PApp::SQL::Database;

=head2 THE DATABASE CLASS

Again (sigh) the problem of persistency. What do you do when you have
to serialize on object that contains (or should contain) a database
handle? Short answer: you don't. Long answer: you can embed the necessary
information to recreate the dbh when needed.

The C<PApp::SQL::Database> class does that, in a relatively efficient
fashion: the overhead is currently a single method call per access (you
can cache the real dbh if you want).

=over 4

=item $db = new <same arguments as C<connect_cached>>

The C<new> call takes the same arguments as C<connect_cached> (obviously,
if you supply a connect callback it better is serializable, see
L<PApp::Callback>!) and returns a serializable database class. No database
handle is actually being created.

=item $db->dbh

Return the database handle as fast as possible (usually just a hash lookup).

=item $db->checked_dbh

Return the database handle, but first check that the database is still
available and re-open the connection if necessary.

=cut

sub new($$;@) {
   my $class = shift;
   my ($id, $dsn, $user, $pass, $flags, $connect) = @_;
   # the following line is duplicated in PApp::SQL::Database::new
   my $id2 = "$id\0$dsn\0$user\0$pass";
   bless [$id2, $flags, $connect], $class;
}

# the following two functions better be fast!
sub dbh($) {
   $dbcache{$_[0][0]} || $_[0]->checked_dbh;
}

sub checked_dbh($) {
   my $dbh = $dbcache{$_[0][0]};
   $dbh && $dbh->ping
      ? $dbh
      : PApp::SQL::connect_cached((split /\x00/, $_[0][0]), $_[0][1], $_[0][2]);
}

=item $db->dsn

Return the DSN (L<DBI>) fo the database object (e.g. for error messages).

=item $db->login

Return the login name.

=item $db->password

Return the password (emphasizing the fact that the apssword is stored plaintext ;)

=cut

sub dsn($) {
   my $self = shift;
   (split /\x00/, $self->[0])[1];
}

sub login($) {
   my $self = shift;
   (split /\x00/, $self->[0])[2];
}

sub password($) {
   my $self = shift;
   (split /\x00/, $self->[0])[3];
}

=back

=cut

1;

=head1 SEE ALSO

L<PApp>.

=head1 AUTHOR

 Marc Lehmann <pcg@goof.com>
 http://www.goof.com/pcg/marc/

=cut

Revision:	1.21
Committed:	Wed Feb 27 04:32:39 2002 UTC (22 years, 2 months ago) by root
Branch:	MAIN
CVS Tags:	Klinik_Kis_25032002_2245
Changes since 1.20:	+6 -3 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.19	PApp::SQL - absolutely easy yet fast and powerful sql access.
4	root	1.1
5			=head1 SYNOPSIS
6
7			use PApp::SQL;
8	root	1.10
9			my $st = sql_exec $DBH, "select ... where a = ?", $a;
10
11			local $DBH = <database handle>;
12			my $st = sql_exec \my($bind_a, $bind_b), "select a,b ...";
13			my $st = sql_insertid
14			sql_exec "insert into ... values (?, ?)", $v1, $v2;
15			my $a = sql_fetch "select a from ...";
16			sql_fetch \my($a, $b), "select a,b ...";
17
18	root	1.20	sql_exists "table where name like 'a%'"
19	root	1.10	or die "a* required but not existent";
20
21			my $db = new PApp::SQL::Database "", "DBI:mysql:test", "user", "pass";
22			local $PApp::SQL::DBH = $db->checked_dbh; # does 'ping'
23
24			sql_exec $db->dbh, "select ...";
25	root	1.1
26			=head1 DESCRIPTION
27
28			This module provides you with easy-to-use functions to execute sql
29			commands (using DBI). Despite being easy to use, they are also quite
30	root	1.10	efficient and allow you to write faster programs in less lines of code. It
31			should work with anything from perl-5.004_01 onwards, but I only support
32	root	1.15	5.005+. UTF8 handling (the C<sql_u*> family of functions) will only be
33			effective with perl version 5.006 and beyond.
34	root	1.10
35			If the descriptions here seem terse or if you always wanted to know
36			what PApp is then have a look at the PApp module which uses this module
37			extensively but also provides you with a lot more gimmicks to play around
38			with to help you create cool applications ;)
39	root	1.1
40			=cut
41
42			package PApp::SQL;
43
44	root	1.10	use DBI ();
45	root	1.1
46			BEGIN {
47	root	1.10	use base qw(Exporter DynaLoader);
48	root	1.1
49	root	1.21	$VERSION = 0.13;
50	root	1.1	@EXPORT = qw(
51	root	1.16	sql_exec sql_fetch sql_fetchall sql_exists sql_insertid $sql_exec
52			sql_uexec sql_ufetch sql_ufetchall sql_uexists
53	root	1.1	);
54			@EXPORT_OK = qw(
55			connect_cached
56			);
57
58	root	1.10	bootstrap PApp::SQL $VERSION;
59	root	1.1	}
60
61			our $sql_exec; # last result of sql_exec's execute call
62			our $DBH; # the default database handle
63	root	1.10	our $Database; # the current SQL::Database object, if applicable
64	root	1.1
65			our %dbcache;
66
67	root	1.10	=head2 GLOBAL VARIABLES
68
69			=over 4
70
71			=item $sql_exec
72
73			Since the C<sql_exec> family of functions return a statement handle there
74			must eb another way to test the return value of the C<execute> call. This
75			global variable contains the result of the most recent call to C<execute>
76			done by this module.
77
78			=item $PApp::SQL::DBH
79
80			The default database handle used by this module if no C<$DBH> was
81			specified as argument and no C<$DBH> is found in the current package. See
82			C<sql_exec> for a discussion.
83
84			=item $PApp::SQL::Database
85
86			The current default C<PApp::SQL::Database>-object. Future versions might
87			automatically fall back on this database and create database handles from
88			it if neccessary. At the moment this is not used by this module but might
89			be nice as a placeholder for the database object that corresponds to
90			$PApp::SQL::DBH.
91
92			=back
93
94			=head2 FUNCTIONS
95
96			=over 4
97
98	root	1.1	=item $dbh = connect_cached $id, $dsn, $user, $pass, $flags, $connect
99
100			(not exported by by default)
101
102			Connect to the database given by C<($dsn,$user,$pass)>, while using the
103			flags from C<$flags>. These are just the same arguments as given to
104			C<DBI->connect>.
105
106	root	1.6	The database handle will be cached under the unique id
107			C<$id\|$dsn\|$user\|$pass>. If the same id is requested later, the
108			cached handle will be checked (using ping), and the connection will
109			be re-established if necessary (be sure to prefix your application or
110			module name to the id to make it "more" unique. Things like __PACKAGE__ .
111			__LINE__ work fine as well).
112
113			The reason C<$id> is necessary is that you might specify special connect
114			arguments or special flags, or you might want to configure your $DBH
115			differently than maybe other applications requesting the same database
116			connection. If none of this is becessary for your application you can
117			leave $id empty (i.e. "").
118	root	1.1
119			If specified, C<$connect> is a callback (e.g. a coderef) that will be
120			called each time a new connection is being established, with the new
121			C<$dbh> as first argument.
122
123			Examples:
124
125			# try your luck opening the papp database without access info
126			$dbh = connect_cached __FILE__, "DBI:mysql:papp";
127
128	root	1.19	Mysql-specific behaviour: The default setting of
129			C<mysql_client_found_rows> is TRUE, you can overwrite this, though.
130	root	1.18
131	root	1.1	=cut
132
133			sub connect_cached {
134			my ($id, $dsn, $user, $pass, $flags, $connect) = @_;
135			# the following line is duplicated in PApp::SQL::Database::new
136			$id = "$id\0$dsn\0$user\0$pass";
137			unless ($dbcache{$id} && $dbcache{$id}->ping) {
138	root	1.5	# first, nuke our statement cache (sooory ;)
139	root	1.1	cachesize cachesize 0;
140	root	1.18
141			# then make mysql behave more standardly by default
142			$dsn =~ /^[Dd][Bb][Ii]:mysql:/
143			and $dsn !~ /;mysql_client_found_rows/
144			and $dsn .= ";mysql_client_found_rows=1";
145
146	root	1.1	# then connect anew
147			$dbcache{$id} =
148			eval { DBI->connect($dsn, $user, $pass, $flags) }
149			\|\| eval { DBI->connect($dsn, $user, $pass, $flags) }
150	root	1.5	\|\| die "unable to connect to database $dsn: $DBI::errstr\n";
151	root	1.1	$connect->($dbcache{$id}) if $connect;
152			}
153			$dbcache{$id};
154			}
155
156			=item $sth = sql_exec [dbh,] [bind-vals...,] "sql-statement", [arguments...]
157
158	root	1.15	=item $sth = sql_uexec <see sql_exec>
159
160	root	1.1	C<sql_exec> is the most important and most-used function in this module.
161
162			Runs the given sql command with the given parameters and returns the
163			statement handle. The command and the statement handle will be cached
164			(with the database handle and the sql string as key), so prepare will be
165			called only once for each distinct sql call (please keep in mind that the
166			returned statement will always be the same, so, if you call C<sql_exec>
167			with the same dbh and sql-statement twice (e.g. in a subroutine you
168			called), the statement handle for the first call mustn't be used.
169
170			The database handle (the first argument) is optional. If it is missing,
171			C<sql_exec> first tries to use the variable C<$DBH> in the current (=
172			calling) package and, if that fails, it tries to use database handle in
173			C<$PApp::SQL::DBH>, which you can set before calling these functions.
174
175			The actual return value from the C<$sth->execute> call is stored in the
176			package-global (and exported) variable C<$sql_exec>.
177
178			If any error occurs C<sql_exec> will throw an exception.
179
180	root	1.15	C<sql_uexec> is similar to C<sql_exec> but upgrades all input arguments to
181			utf8 before calling the C<execute> method.
182
183	root	1.1	Examples:
184
185			# easy one
186			my $st = sql_exec "select name, id from table where id = ?", $id;
187			while (my ($name, $id) = $st->fetchrow_array) { ... };
188
189			# the fastest way to use dbi, using bind_columns
190			my $st = sql_exec \my($name, $id),
191			"select name, id from table where id = ?",
192			$id;
193			while ($st->fetch) { ...}
194
195			# now use a different dastabase:
196			sql_exec $dbh, "update file set name = ?", "oops.txt";
197
198
199			=item sql_fetch <see sql_exec>
200
201	root	1.15	=item sql_ufetch <see sql_uexec>
202
203			Execute an sql-statement and fetch the first row of results. Depending on
204	root	1.1	the caller context the row will be returned as a list (array context), or
205			just the first columns. In table form:
206
207			CONTEXT RESULT
208			void ()
209			scalar first column
210			list array
211
212			C<sql_fetch> is quite efficient in conjunction with bind variables:
213
214			sql_fetch \my($name, $amount),
215			"select name, amount from table where id name = ?",
216			"Toytest";
217
218			But of course the normal way to call it is simply:
219
220			my($name, $amount) = sql_fetch "select ...", args...
221
222			... and it's still quite fast unless you fetch large amounts of data.
223
224	root	1.15	C<sql_ufetch> is similar to C<sql_fetch> but upgrades all input values to
225	root	1.21	utf8 and forces all result values to utf8 (this does I<not> include result
226			parameters, only return values. Using bind variables in cinjunction with
227			sql_u* functions results in undefined behaviour).
228	root	1.15
229	root	1.1	=item sql_fetchall <see sql_exec>
230
231	root	1.15	=item sql_ufetchall <see sql_uexec>
232
233	root	1.1	Similarly to C<sql_fetch>, but all result rows will be fetched (this is
234			of course inefficient for large results!). The context is ignored (only
235			list context makes sense), but the result still depends on the number of
236			columns in the result:
237
238			COLUMNS RESULT
239			0 ()
240			1 (row1, row2, row3...)
241			many ([row1], [row2], [row3]...)
242
243			Examples (all of which are inefficient):
244
245			for (sql_fetchall "select id from table") { ... }
246
247			my @names = sql_fetchall "select name from user";
248
249			for (sql_fetchall "select name, age, place from user") {
250			my ($name, $age, $place) = @$_;
251			}
252
253	root	1.15	C<sql_ufetchall> is similar to C<sql_fetchall> but upgrades all input
254	root	1.21	values to utf8 and forces all result values to utf8 (see the caveats in
255			the description of C<sql_ufetch>, though).
256	root	1.15
257	root	1.20	=item sql_exists "<table_references> where <where_condition>...", args...
258	root	1.1
259	root	1.15	=item sql_uexists <see sql_exists>
260
261	root	1.1	Check wether the result of the sql-statement "select xxx from
262			$first_argument" would be empty or not (that is, imagine the string
263	root	1.13	"select * from" were prepended to your statement (it isn't)). Should work
264	root	1.1	with every database but can be quite slow, except on mysql, where this
265			should be quite fast.
266
267	root	1.15	C<sql_uexists> is similar to C<sql_exists> but upgrades all parameters to
268			utf8.
269
270	root	1.1	Examples:
271
272			print "user 7 exists!\n"
273			if sql_exists "user where id = ?", 7;
274
275			die "duplicate key"
276			if sql_exists "user where name = ? and pass = ?", "stefan", "geheim";
277
278			=cut
279
280	root	1.3	=item $lastid = sql_insertid $sth
281
282	root	1.8	Returns the last automatically created key value. It must be executed
283			directly after executing the insert statement that created it. This is
284			what is actually returned for various databases. If your database is
285			missing, please send me an e-mail on how to implement this ;)
286
287			mysql: first C<AUTO_INCREMENT> column set to NULL
288			postgres: C<oid> column (is there a way to get the last SERIAL?)
289			sybase: C<IDENTITY> column of the last insert (slow)
290			informix: C<SERIAL> or C<SERIAL8> column of the last insert
291
292			Except for sybase, this does not require a server access.
293	root	1.3
294			=cut
295
296			sub sql_insertid($) {
297			my $sth = shift or die "sql_insertid requires a statement handle";
298			my $dbh = $sth->{Database};
299			my $driver = $dbh->{Driver}{Name};
300
301	root	1.8	$driver eq "mysql" and return $sth->{mysql_insertid};
302			$driver eq "Pg" and return $sth->{pg_oid_status};
303			$driver eq "Sybase" and return sql_fetch($dbh, 'SELECT @@IDENTITY');
304	root	1.3	$driver eq "Informix" and return $sth->{ix_sqlerrd}[1];
305
306			die "sql_insertid does not spport the dbd driver '$driver', please see PApp::SQL::sql_insertid";
307	root	1.1	}
308
309			=item [old-size] = cachesize [new-size]
310
311			Returns (and possibly changes) the LRU cache size used by C<sql_exec>. The
312			default is somewhere around 50 (= the 50 last recently used statements
313			will be cached). It shouldn't be too large, since a simple linear listed
314			is used for the cache at the moment (which, for small (<100) cache sizes
315			is actually quite fast).
316
317			The function always returns the cache size in effect I<before> the call,
318			so, to nuke the cache (for example, when a database connection has died
319			or you want to garbage collect old database/statement handles), this
320			construct can be used:
321
322			PApp::SQL::cachesize PApp::SQL::cachesize 0;
323
324			=cut
325
326			=item reinitialize [not exported]
327
328	root	1.9	Clears any internal caches (statement cache, database handle
329			cache). Should be called after C<fork> and other accidents that invalidate
330			database handles.
331	root	1.1
332			=cut
333
334			sub reinitialize {
335			cachesize cachesize 0;
336			for (values %dbcache) {
337	root	1.11	eval { $_->{InactiveDestroy} = 1 };
338	root	1.1	}
339			undef %dbcache;
340			}
341
342			=back
343
344			=cut
345
346	root	1.7	reinitialize;
347
348	root	1.1	package PApp::SQL::Database;
349
350			=head2 THE DATABASE CLASS
351
352	root	1.15	Again (sigh) the problem of persistency. What do you do when you have
353			to serialize on object that contains (or should contain) a database
354			handle? Short answer: you don't. Long answer: you can embed the necessary
355			information to recreate the dbh when needed.
356	root	1.1
357			The C<PApp::SQL::Database> class does that, in a relatively efficient
358			fashion: the overhead is currently a single method call per access (you
359			can cache the real dbh if you want).
360
361			=over 4
362
363			=item $db = new <same arguments as C<connect_cached>>
364
365			The C<new> call takes the same arguments as C<connect_cached> (obviously,
366			if you supply a connect callback it better is serializable, see
367			L<PApp::Callback>!) and returns a serializable database class. No database
368			handle is actually being created.
369
370			=item $db->dbh
371
372			Return the database handle as fast as possible (usually just a hash lookup).
373
374			=item $db->checked_dbh
375
376			Return the database handle, but first check that the database is still
377			available and re-open the connection if necessary.
378
379			=cut
380
381			sub new($$;@) {
382			my $class = shift;
383			my ($id, $dsn, $user, $pass, $flags, $connect) = @_;
384			# the following line is duplicated in PApp::SQL::Database::new
385			my $id2 = "$id\0$dsn\0$user\0$pass";
386			bless [$id2, $flags, $connect], $class;
387			}
388
389			# the following two functions better be fast!
390			sub dbh($) {
391			$dbcache{$_[0][0]} \|\| $_[0]->checked_dbh;
392			}
393
394			sub checked_dbh($) {
395			my $dbh = $dbcache{$_[0][0]};
396			$dbh && $dbh->ping
397			? $dbh
398			: PApp::SQL::connect_cached((split /\x00/, $_[0][0]), $_[0][1], $_[0][2]);
399			}
400
401			=item $db->dsn
402
403			Return the DSN (L<DBI>) fo the database object (e.g. for error messages).
404
405	root	1.14	=item $db->login
406
407			Return the login name.
408
409			=item $db->password
410
411			Return the password (emphasizing the fact that the apssword is stored plaintext ;)
412
413	root	1.1	=cut
414
415			sub dsn($) {
416			my $self = shift;
417	root	1.9	(split /\x00/, $self->[0])[1];
418	root	1.14	}
419
420			sub login($) {
421			my $self = shift;
422			(split /\x00/, $self->[0])[2];
423			}
424
425			sub password($) {
426			my $self = shift;
427			(split /\x00/, $self->[0])[3];
428	root	1.1	}
429
430			=back
431
432			=cut
433
434			1;
435
436			=head1 SEE ALSO
437
438			L<PApp>.
439
440			=head1 AUTHOR
441
442			Marc Lehmann <pcg@goof.com>
443			http://www.goof.com/pcg/marc/
444
445			=cut
446