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 = 0.143;
   @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
UTF-8 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
UTF-8 and forces all result values to UTF-8 (this does I<not> include result
parameters, only return values. Using bind variables in conjunction with
sql_u* functions might result in undefined behaviour - we use UTF-8 on
bind-variables at execution time and it seems to work on DBD::mysql as it
ignores the UTF-8 bit completely. Which just means that that DBD-driver is
broken).

=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 UTF-8 and forces all result values to UTF-8 (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
UTF-8.

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:	1.31
Committed:	Wed Jan 28 19:58:19 2004 UTC (20 years, 3 months ago) by root
Branch:	MAIN
Changes since 1.30:	+9 -8 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	stefan	1.30	$VERSION = 0.143;
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	root	1.31	UTF-8 before calling the C<execute> method.
192	root	1.15
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, $amount) = sql_fetch "select ...", args...
231
232			... and it's still quite fast unless you fetch large amounts of data.
233
234	root	1.15	C<sql_ufetch> is similar to C<sql_fetch> but upgrades all input values to
235	root	1.31	UTF-8 and forces all result values to UTF-8 (this does I<not> include result
236			parameters, only return values. Using bind variables in conjunction with
237			sql_u* functions might result in undefined behaviour - we use UTF-8 on
238			bind-variables at execution time and it seems to work on DBD::mysql as it
239			ignores the UTF-8 bit completely. Which just means that that DBD-driver is
240			broken).
241	root	1.15
242	root	1.1	=item sql_fetchall <see sql_exec>
243
244	root	1.15	=item sql_ufetchall <see sql_uexec>
245
246	root	1.1	Similarly to C<sql_fetch>, but all result rows will be fetched (this is
247			of course inefficient for large results!). The context is ignored (only
248			list context makes sense), but the result still depends on the number of
249			columns in the result:
250
251			COLUMNS RESULT
252			0 ()
253			1 (row1, row2, row3...)
254			many ([row1], [row2], [row3]...)
255
256			Examples (all of which are inefficient):
257
258			for (sql_fetchall "select id from table") { ... }
259
260			my @names = sql_fetchall "select name from user";
261
262			for (sql_fetchall "select name, age, place from user") {
263			my ($name, $age, $place) = @$_;
264			}
265
266	root	1.15	C<sql_ufetchall> is similar to C<sql_fetchall> but upgrades all input
267	root	1.31	values to UTF-8 and forces all result values to UTF-8 (see the caveats in
268	root	1.21	the description of C<sql_ufetch>, though).
269	root	1.15
270	root	1.20	=item sql_exists "<table_references> where <where_condition>...", args...
271	root	1.1
272	root	1.15	=item sql_uexists <see sql_exists>
273
274	root	1.1	Check wether the result of the sql-statement "select xxx from
275			$first_argument" would be empty or not (that is, imagine the string
276	root	1.13	"select * from" were prepended to your statement (it isn't)). Should work
277	root	1.1	with every database but can be quite slow, except on mysql, where this
278			should be quite fast.
279
280	root	1.15	C<sql_uexists> is similar to C<sql_exists> but upgrades all parameters to
281	root	1.31	UTF-8.
282	root	1.15
283	root	1.1	Examples:
284
285			print "user 7 exists!\n"
286			if sql_exists "user where id = ?", 7;
287
288			die "duplicate key"
289			if sql_exists "user where name = ? and pass = ?", "stefan", "geheim";
290
291			=cut
292
293	root	1.3	=item $lastid = sql_insertid $sth
294
295	root	1.8	Returns the last automatically created key value. It must be executed
296			directly after executing the insert statement that created it. This is
297			what is actually returned for various databases. If your database is
298			missing, please send me an e-mail on how to implement this ;)
299
300			mysql: first C<AUTO_INCREMENT> column set to NULL
301			postgres: C<oid> column (is there a way to get the last SERIAL?)
302			sybase: C<IDENTITY> column of the last insert (slow)
303			informix: C<SERIAL> or C<SERIAL8> column of the last insert
304
305			Except for sybase, this does not require a server access.
306	root	1.3
307			=cut
308
309			sub sql_insertid($) {
310			my $sth = shift or die "sql_insertid requires a statement handle";
311			my $dbh = $sth->{Database};
312			my $driver = $dbh->{Driver}{Name};
313
314	root	1.8	$driver eq "mysql" and return $sth->{mysql_insertid};
315			$driver eq "Pg" and return $sth->{pg_oid_status};
316			$driver eq "Sybase" and return sql_fetch($dbh, 'SELECT @@IDENTITY');
317	root	1.3	$driver eq "Informix" and return $sth->{ix_sqlerrd}[1];
318
319			die "sql_insertid does not spport the dbd driver '$driver', please see PApp::SQL::sql_insertid";
320	root	1.1	}
321
322			=item [old-size] = cachesize [new-size]
323
324			Returns (and possibly changes) the LRU cache size used by C<sql_exec>. The
325			default is somewhere around 50 (= the 50 last recently used statements
326	root	1.26	will be cached). It shouldn't be too large, since a simple linear list
327	root	1.1	is used for the cache at the moment (which, for small (<100) cache sizes
328			is actually quite fast).
329
330			The function always returns the cache size in effect I<before> the call,
331			so, to nuke the cache (for example, when a database connection has died
332			or you want to garbage collect old database/statement handles), this
333			construct can be used:
334
335			PApp::SQL::cachesize PApp::SQL::cachesize 0;
336
337			=cut
338
339			=item reinitialize [not exported]
340
341	root	1.9	Clears any internal caches (statement cache, database handle
342			cache). Should be called after C<fork> and other accidents that invalidate
343			database handles.
344	root	1.1
345			=cut
346
347			sub reinitialize {
348			cachesize cachesize 0;
349			for (values %dbcache) {
350	root	1.11	eval { $_->{InactiveDestroy} = 1 };
351	root	1.1	}
352			undef %dbcache;
353			}
354
355			=back
356
357			=cut
358
359	root	1.7	reinitialize;
360
361	root	1.1	package PApp::SQL::Database;
362
363			=head2 THE DATABASE CLASS
364
365	root	1.15	Again (sigh) the problem of persistency. What do you do when you have
366			to serialize on object that contains (or should contain) a database
367			handle? Short answer: you don't. Long answer: you can embed the necessary
368			information to recreate the dbh when needed.
369	root	1.1
370			The C<PApp::SQL::Database> class does that, in a relatively efficient
371			fashion: the overhead is currently a single method call per access (you
372			can cache the real dbh if you want).
373
374			=over 4
375
376			=item $db = new <same arguments as C<connect_cached>>
377
378			The C<new> call takes the same arguments as C<connect_cached> (obviously,
379			if you supply a connect callback it better is serializable, see
380			L<PApp::Callback>!) and returns a serializable database class. No database
381			handle is actually being created.
382
383			=item $db->dbh
384
385			Return the database handle as fast as possible (usually just a hash lookup).
386
387			=item $db->checked_dbh
388
389			Return the database handle, but first check that the database is still
390			available and re-open the connection if necessary.
391
392			=cut
393
394			sub new($$;@) {
395			my $class = shift;
396			my ($id, $dsn, $user, $pass, $flags, $connect) = @_;
397			# the following line is duplicated in PApp::SQL::Database::new
398			my $id2 = "$id\0$dsn\0$user\0$pass";
399			bless [$id2, $flags, $connect], $class;
400			}
401
402			# the following two functions better be fast!
403			sub dbh($) {
404			$dbcache{$_[0][0]} \|\| $_[0]->checked_dbh;
405			}
406
407			sub checked_dbh($) {
408			my $dbh = $dbcache{$_[0][0]};
409			$dbh && $dbh->ping
410			? $dbh
411			: PApp::SQL::connect_cached((split /\x00/, $_[0][0]), $_[0][1], $_[0][2]);
412			}
413
414			=item $db->dsn
415
416			Return the DSN (L<DBI>) fo the database object (e.g. for error messages).
417
418	root	1.14	=item $db->login
419
420			Return the login name.
421
422			=item $db->password
423
424	root	1.25	Return the password (emphasizing the fact that the password is stored plaintext ;)
425	root	1.14
426	root	1.1	=cut
427
428			sub dsn($) {
429			my $self = shift;
430	root	1.9	(split /\x00/, $self->[0])[1];
431	root	1.14	}
432
433			sub login($) {
434			my $self = shift;
435			(split /\x00/, $self->[0])[2];
436			}
437
438			sub password($) {
439			my $self = shift;
440			(split /\x00/, $self->[0])[3];
441	root	1.1	}
442
443			=back
444
445			=cut
446
447			1;
448
449			=head1 SEE ALSO
450
451			L<PApp>.
452
453			=head1 AUTHOR
454
455			Marc Lehmann <pcg@goof.com>
456			http://www.goof.com/pcg/marc/
457
458			=cut
459