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 = 0.141;
   @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 be 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. 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 $DBH
differently than maybe other applications requesting the same database
connection. If none of this is necessary for your application you can
leave C<$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 not be in use
anymore, as the subsequent call will re-use the handle.

The database handle (the first argument) is optional. If it is missing,
it tries to use database handle in C<$PApp::SQL::DBH>, which you can set
before calling these functions. NOTICE: future and former versions of
PApp::SQL might also look up the global variable C<$DBH> in the callers
package.

=begin comment

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.

=end comment

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 list
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 password 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:	1.28
Committed:	Sat Nov 2 03:33:49 2002 UTC (21 years, 6 months ago) by root
Branch:	MAIN
Changes since 1.27:	+1 -1 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	1.28	$VERSION = 0.141;
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	root	1.22	must be another way to test the return value of the C<execute> call. This
75	root	1.10	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	root	1.24	specified as argument. See C<sql_exec> for a discussion.
82	root	1.10
83			=item $PApp::SQL::Database
84
85			The current default C<PApp::SQL::Database>-object. Future versions might
86			automatically fall back on this database and create database handles from
87			it if neccessary. At the moment this is not used by this module but might
88			be nice as a placeholder for the database object that corresponds to
89			$PApp::SQL::DBH.
90
91			=back
92
93			=head2 FUNCTIONS
94
95			=over 4
96
97	root	1.1	=item $dbh = connect_cached $id, $dsn, $user, $pass, $flags, $connect
98
99			(not exported by by default)
100
101			Connect to the database given by C<($dsn,$user,$pass)>, while using the
102			flags from C<$flags>. These are just the same arguments as given to
103			C<DBI->connect>.
104
105	root	1.6	The database handle will be cached under the unique id
106			C<$id\|$dsn\|$user\|$pass>. If the same id is requested later, the
107			cached handle will be checked (using ping), and the connection will
108			be re-established if necessary (be sure to prefix your application or
109			module name to the id to make it "more" unique. Things like __PACKAGE__ .
110			__LINE__ work fine as well).
111
112			The reason C<$id> is necessary is that you might specify special connect
113			arguments or special flags, or you might want to configure your $DBH
114			differently than maybe other applications requesting the same database
115	root	1.22	connection. If none of this is necessary for your application you can
116			leave C<$id> empty (i.e. "").
117	root	1.1
118			If specified, C<$connect> is a callback (e.g. a coderef) that will be
119			called each time a new connection is being established, with the new
120			C<$dbh> as first argument.
121
122			Examples:
123
124			# try your luck opening the papp database without access info
125			$dbh = connect_cached __FILE__, "DBI:mysql:papp";
126
127	root	1.19	Mysql-specific behaviour: The default setting of
128			C<mysql_client_found_rows> is TRUE, you can overwrite this, though.
129	root	1.18
130	root	1.1	=cut
131
132			sub connect_cached {
133			my ($id, $dsn, $user, $pass, $flags, $connect) = @_;
134			# the following line is duplicated in PApp::SQL::Database::new
135			$id = "$id\0$dsn\0$user\0$pass";
136			unless ($dbcache{$id} && $dbcache{$id}->ping) {
137	root	1.5	# first, nuke our statement cache (sooory ;)
138	root	1.1	cachesize cachesize 0;
139	root	1.18
140			# then make mysql behave more standardly by default
141			$dsn =~ /^[Dd][Bb][Ii]:mysql:/
142			and $dsn !~ /;mysql_client_found_rows/
143			and $dsn .= ";mysql_client_found_rows=1";
144
145	root	1.1	# then connect anew
146			$dbcache{$id} =
147			eval { DBI->connect($dsn, $user, $pass, $flags) }
148			\|\| eval { DBI->connect($dsn, $user, $pass, $flags) }
149	root	1.5	\|\| die "unable to connect to database $dsn: $DBI::errstr\n";
150	root	1.1	$connect->($dbcache{$id}) if $connect;
151			}
152			$dbcache{$id};
153			}
154
155			=item $sth = sql_exec [dbh,] [bind-vals...,] "sql-statement", [arguments...]
156
157	root	1.15	=item $sth = sql_uexec <see sql_exec>
158
159	root	1.1	C<sql_exec> is the most important and most-used function in this module.
160
161			Runs the given sql command with the given parameters and returns the
162			statement handle. The command and the statement handle will be cached
163			(with the database handle and the sql string as key), so prepare will be
164			called only once for each distinct sql call (please keep in mind that the
165			returned statement will always be the same, so, if you call C<sql_exec>
166			with the same dbh and sql-statement twice (e.g. in a subroutine you
167	root	1.23	called), the statement handle for the first call mustn't not be in use
168			anymore, as the subsequent call will re-use the handle.
169	root	1.1
170			The database handle (the first argument) is optional. If it is missing,
171	root	1.24	it tries to use database handle in C<$PApp::SQL::DBH>, which you can set
172			before calling these functions. NOTICE: future and former versions of
173			PApp::SQL might also look up the global variable C<$DBH> in the callers
174			package.
175
176			=begin comment
177
178			If it is missing, C<sql_exec> first tries to use the variable C<$DBH>
179			in the current (= calling) package and, if that fails, it tries to use
180			database handle in C<$PApp::SQL::DBH>, which you can set before calling
181			these functions.
182
183			=end comment
184	root	1.1
185			The actual return value from the C<$sth->execute> call is stored in the
186			package-global (and exported) variable C<$sql_exec>.
187
188			If any error occurs C<sql_exec> will throw an exception.
189
190	root	1.15	C<sql_uexec> is similar to C<sql_exec> but upgrades all input arguments to
191			utf8 before calling the C<execute> method.
192
193	root	1.1	Examples:
194
195			# easy one
196			my $st = sql_exec "select name, id from table where id = ?", $id;
197			while (my ($name, $id) = $st->fetchrow_array) { ... };
198
199			# the fastest way to use dbi, using bind_columns
200			my $st = sql_exec \my($name, $id),
201			"select name, id from table where id = ?",
202			$id;
203			while ($st->fetch) { ...}
204
205			# now use a different dastabase:
206			sql_exec $dbh, "update file set name = ?", "oops.txt";
207
208
209			=item sql_fetch <see sql_exec>
210
211	root	1.15	=item sql_ufetch <see sql_uexec>
212
213			Execute an sql-statement and fetch the first row of results. Depending on
214	root	1.1	the caller context the row will be returned as a list (array context), or
215			just the first columns. In table form:
216
217			CONTEXT RESULT
218			void ()
219			scalar first column
220			list array
221
222			C<sql_fetch> is quite efficient in conjunction with bind variables:
223
224			sql_fetch \my($name, $amount),
225			"select name, amount from table where id name = ?",
226			"Toytest";
227
228			But of course the normal way to call it is simply:
229
230			my($name, $amount) = sql_fetch "select ...", args...
231
232			... and it's still quite fast unless you fetch large amounts of data.
233
234	root	1.15	C<sql_ufetch> is similar to C<sql_fetch> but upgrades all input values to
235	root	1.21	utf8 and forces all result values to utf8 (this does I<not> include result
236			parameters, only return values. Using bind variables in cinjunction with
237			sql_u* functions results in undefined behaviour).
238	root	1.15
239	root	1.1	=item sql_fetchall <see sql_exec>
240
241	root	1.15	=item sql_ufetchall <see sql_uexec>
242
243	root	1.1	Similarly to C<sql_fetch>, but all result rows will be fetched (this is
244			of course inefficient for large results!). The context is ignored (only
245			list context makes sense), but the result still depends on the number of
246			columns in the result:
247
248			COLUMNS RESULT
249			0 ()
250			1 (row1, row2, row3...)
251			many ([row1], [row2], [row3]...)
252
253			Examples (all of which are inefficient):
254
255			for (sql_fetchall "select id from table") { ... }
256
257			my @names = sql_fetchall "select name from user";
258
259			for (sql_fetchall "select name, age, place from user") {
260			my ($name, $age, $place) = @$_;
261			}
262
263	root	1.15	C<sql_ufetchall> is similar to C<sql_fetchall> but upgrades all input
264	root	1.21	values to utf8 and forces all result values to utf8 (see the caveats in
265			the description of C<sql_ufetch>, though).
266	root	1.15
267	root	1.20	=item sql_exists "<table_references> where <where_condition>...", args...
268	root	1.1
269	root	1.15	=item sql_uexists <see sql_exists>
270
271	root	1.1	Check wether the result of the sql-statement "select xxx from
272			$first_argument" would be empty or not (that is, imagine the string
273	root	1.13	"select * from" were prepended to your statement (it isn't)). Should work
274	root	1.1	with every database but can be quite slow, except on mysql, where this
275			should be quite fast.
276
277	root	1.15	C<sql_uexists> is similar to C<sql_exists> but upgrades all parameters to
278			utf8.
279
280	root	1.1	Examples:
281
282			print "user 7 exists!\n"
283			if sql_exists "user where id = ?", 7;
284
285			die "duplicate key"
286			if sql_exists "user where name = ? and pass = ?", "stefan", "geheim";
287
288			=cut
289
290	root	1.3	=item $lastid = sql_insertid $sth
291
292	root	1.8	Returns the last automatically created key value. It must be executed
293			directly after executing the insert statement that created it. This is
294			what is actually returned for various databases. If your database is
295			missing, please send me an e-mail on how to implement this ;)
296
297			mysql: first C<AUTO_INCREMENT> column set to NULL
298			postgres: C<oid> column (is there a way to get the last SERIAL?)
299			sybase: C<IDENTITY> column of the last insert (slow)
300			informix: C<SERIAL> or C<SERIAL8> column of the last insert
301
302			Except for sybase, this does not require a server access.
303	root	1.3
304			=cut
305
306			sub sql_insertid($) {
307			my $sth = shift or die "sql_insertid requires a statement handle";
308			my $dbh = $sth->{Database};
309			my $driver = $dbh->{Driver}{Name};
310
311	root	1.8	$driver eq "mysql" and return $sth->{mysql_insertid};
312			$driver eq "Pg" and return $sth->{pg_oid_status};
313			$driver eq "Sybase" and return sql_fetch($dbh, 'SELECT @@IDENTITY');
314	root	1.3	$driver eq "Informix" and return $sth->{ix_sqlerrd}[1];
315
316			die "sql_insertid does not spport the dbd driver '$driver', please see PApp::SQL::sql_insertid";
317	root	1.1	}
318
319			=item [old-size] = cachesize [new-size]
320
321			Returns (and possibly changes) the LRU cache size used by C<sql_exec>. The
322			default is somewhere around 50 (= the 50 last recently used statements
323	root	1.26	will be cached). It shouldn't be too large, since a simple linear list
324	root	1.1	is used for the cache at the moment (which, for small (<100) cache sizes
325			is actually quite fast).
326
327			The function always returns the cache size in effect I<before> the call,
328			so, to nuke the cache (for example, when a database connection has died
329			or you want to garbage collect old database/statement handles), this
330			construct can be used:
331
332			PApp::SQL::cachesize PApp::SQL::cachesize 0;
333
334			=cut
335
336			=item reinitialize [not exported]
337
338	root	1.9	Clears any internal caches (statement cache, database handle
339			cache). Should be called after C<fork> and other accidents that invalidate
340			database handles.
341	root	1.1
342			=cut
343
344			sub reinitialize {
345			cachesize cachesize 0;
346			for (values %dbcache) {
347	root	1.11	eval { $_->{InactiveDestroy} = 1 };
348	root	1.1	}
349			undef %dbcache;
350			}
351
352			=back
353
354			=cut
355
356	root	1.7	reinitialize;
357
358	root	1.1	package PApp::SQL::Database;
359
360			=head2 THE DATABASE CLASS
361
362	root	1.15	Again (sigh) the problem of persistency. What do you do when you have
363			to serialize on object that contains (or should contain) a database
364			handle? Short answer: you don't. Long answer: you can embed the necessary
365			information to recreate the dbh when needed.
366	root	1.1
367			The C<PApp::SQL::Database> class does that, in a relatively efficient
368			fashion: the overhead is currently a single method call per access (you
369			can cache the real dbh if you want).
370
371			=over 4
372
373			=item $db = new <same arguments as C<connect_cached>>
374
375			The C<new> call takes the same arguments as C<connect_cached> (obviously,
376			if you supply a connect callback it better is serializable, see
377			L<PApp::Callback>!) and returns a serializable database class. No database
378			handle is actually being created.
379
380			=item $db->dbh
381
382			Return the database handle as fast as possible (usually just a hash lookup).
383
384			=item $db->checked_dbh
385
386			Return the database handle, but first check that the database is still
387			available and re-open the connection if necessary.
388
389			=cut
390
391			sub new($$;@) {
392			my $class = shift;
393			my ($id, $dsn, $user, $pass, $flags, $connect) = @_;
394			# the following line is duplicated in PApp::SQL::Database::new
395			my $id2 = "$id\0$dsn\0$user\0$pass";
396			bless [$id2, $flags, $connect], $class;
397			}
398
399			# the following two functions better be fast!
400			sub dbh($) {
401			$dbcache{$_[0][0]} \|\| $_[0]->checked_dbh;
402			}
403
404			sub checked_dbh($) {
405			my $dbh = $dbcache{$_[0][0]};
406			$dbh && $dbh->ping
407			? $dbh
408			: PApp::SQL::connect_cached((split /\x00/, $_[0][0]), $_[0][1], $_[0][2]);
409			}
410
411			=item $db->dsn
412
413			Return the DSN (L<DBI>) fo the database object (e.g. for error messages).
414
415	root	1.14	=item $db->login
416
417			Return the login name.
418
419			=item $db->password
420
421	root	1.25	Return the password (emphasizing the fact that the password is stored plaintext ;)
422	root	1.14
423	root	1.1	=cut
424
425			sub dsn($) {
426			my $self = shift;
427	root	1.9	(split /\x00/, $self->[0])[1];
428	root	1.14	}
429
430			sub login($) {
431			my $self = shift;
432			(split /\x00/, $self->[0])[2];
433			}
434
435			sub password($) {
436			my $self = shift;
437			(split /\x00/, $self->[0])[3];
438	root	1.1	}
439
440			=back
441
442			=cut
443
444			1;
445
446			=head1 SEE ALSO
447
448			L<PApp>.
449
450			=head1 AUTHOR
451
452			Marc Lehmann <pcg@goof.com>
453			http://www.goof.com/pcg/marc/
454
455			=cut
456