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=head1 NAME |
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|
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PApp::SQL - absolutely easy yet fast and powerful sql access |
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|
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=head1 SYNOPSIS |
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|
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use PApp::SQL; |
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|
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my $st = sql_exec $DBH, "select ... where a = ?", $a; |
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|
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local $DBH = <database handle>; |
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my $st = sql_exec \my($bind_a, $bind_b), "select a,b ..."; |
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my $st = sql_insertid |
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sql_exec "insert into ... values (?, ?)", $v1, $v2; |
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my $a = sql_fetch "select a from ..."; |
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sql_fetch \my($a, $b), "select a,b ..."; |
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|
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sql_exists "name from table where name like 'a%'" |
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or die "a* required but not existent"; |
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|
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my $db = new PApp::SQL::Database "", "DBI:mysql:test", "user", "pass"; |
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local $PApp::SQL::DBH = $db->checked_dbh; # does 'ping' |
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|
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sql_exec $db->dbh, "select ..."; |
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|
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=head1 DESCRIPTION |
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|
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This module provides you with easy-to-use functions to execute sql |
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commands (using DBI). Despite being easy to use, they are also quite |
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efficient and allow you to write faster programs in less lines of code. It |
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should work with anything from perl-5.004_01 onwards, but I only support |
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5.005+. UTF8 handling (the C<sql_u*> family of functions) will only be |
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effective with perl version 5.006 and beyond. |
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|
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If the descriptions here seem terse or if you always wanted to know |
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what PApp is then have a look at the PApp module which uses this module |
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extensively but also provides you with a lot more gimmicks to play around |
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with to help you create cool applications ;) |
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|
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=cut |
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|
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package PApp::SQL; |
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|
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use DBI (); |
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|
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BEGIN { |
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use base qw(Exporter DynaLoader); |
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|
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$VERSION = 0.124; |
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@EXPORT = qw( |
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sql_exec sql_fetch sql_fetchall sql_exists sql_insertid $sql_exec |
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sql_uexec sql_ufetch sql_ufetchall sql_uexists |
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); |
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@EXPORT_OK = qw( |
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connect_cached |
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); |
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|
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bootstrap PApp::SQL $VERSION; |
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} |
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|
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our $sql_exec; # last result of sql_exec's execute call |
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our $DBH; # the default database handle |
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our $Database; # the current SQL::Database object, if applicable |
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|
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our %dbcache; |
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|
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=head2 GLOBAL VARIABLES |
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|
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=over 4 |
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|
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=item $sql_exec |
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|
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Since the C<sql_exec> family of functions return a statement handle there |
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must eb another way to test the return value of the C<execute> call. This |
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global variable contains the result of the most recent call to C<execute> |
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done by this module. |
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|
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=item $PApp::SQL::DBH |
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|
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The default database handle used by this module if no C<$DBH> was |
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specified as argument and no C<$DBH> is found in the current package. See |
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C<sql_exec> for a discussion. |
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|
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=item $PApp::SQL::Database |
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|
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The current default C<PApp::SQL::Database>-object. Future versions might |
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automatically fall back on this database and create database handles from |
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it if neccessary. At the moment this is not used by this module but might |
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be nice as a placeholder for the database object that corresponds to |
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$PApp::SQL::DBH. |
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|
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=back |
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|
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=head2 FUNCTIONS |
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|
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=over 4 |
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|
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=item $dbh = connect_cached $id, $dsn, $user, $pass, $flags, $connect |
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|
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(not exported by by default) |
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|
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Connect to the database given by C<($dsn,$user,$pass)>, while using the |
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flags from C<$flags>. These are just the same arguments as given to |
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C<DBI->connect>. |
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|
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The database handle will be cached under the unique id |
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C<$id|$dsn|$user|$pass>. If the same id is requested later, the |
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cached handle will be checked (using ping), and the connection will |
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be re-established if necessary (be sure to prefix your application or |
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module name to the id to make it "more" unique. Things like __PACKAGE__ . |
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__LINE__ work fine as well). |
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|
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The reason C<$id> is necessary is that you might specify special connect |
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arguments or special flags, or you might want to configure your $DBH |
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differently than maybe other applications requesting the same database |
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connection. If none of this is becessary for your application you can |
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leave $id empty (i.e. ""). |
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|
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If specified, C<$connect> is a callback (e.g. a coderef) that will be |
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called each time a new connection is being established, with the new |
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C<$dbh> as first argument. |
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|
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Examples: |
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|
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# try your luck opening the papp database without access info |
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$dbh = connect_cached __FILE__, "DBI:mysql:papp"; |
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|
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=cut |
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|
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sub connect_cached { |
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my ($id, $dsn, $user, $pass, $flags, $connect) = @_; |
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# the following line is duplicated in PApp::SQL::Database::new |
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$id = "$id\0$dsn\0$user\0$pass"; |
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unless ($dbcache{$id} && $dbcache{$id}->ping) { |
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#warn "connecting to ($dsn|$user|$pass|$flags)\n";#d# |
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# first, nuke our statement cache (sooory ;) |
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cachesize cachesize 0; |
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# then connect anew |
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$dbcache{$id} = |
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eval { DBI->connect($dsn, $user, $pass, $flags) } |
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|| eval { DBI->connect($dsn, $user, $pass, $flags) } |
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|| die "unable to connect to database $dsn: $DBI::errstr\n"; |
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$connect->($dbcache{$id}) if $connect; |
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} |
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$dbcache{$id}; |
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} |
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|
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=item $sth = sql_exec [dbh,] [bind-vals...,] "sql-statement", [arguments...] |
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|
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=item $sth = sql_uexec <see sql_exec> |
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|
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C<sql_exec> is the most important and most-used function in this module. |
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|
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Runs the given sql command with the given parameters and returns the |
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statement handle. The command and the statement handle will be cached |
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(with the database handle and the sql string as key), so prepare will be |
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called only once for each distinct sql call (please keep in mind that the |
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returned statement will always be the same, so, if you call C<sql_exec> |
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with the same dbh and sql-statement twice (e.g. in a subroutine you |
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called), the statement handle for the first call mustn't be used. |
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|
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The database handle (the first argument) is optional. If it is missing, |
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C<sql_exec> first tries to use the variable C<$DBH> in the current (= |
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calling) package and, if that fails, it tries to use database handle in |
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C<$PApp::SQL::DBH>, which you can set before calling these functions. |
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|
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The actual return value from the C<$sth->execute> call is stored in the |
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package-global (and exported) variable C<$sql_exec>. |
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|
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If any error occurs C<sql_exec> will throw an exception. |
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|
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C<sql_uexec> is similar to C<sql_exec> but upgrades all input arguments to |
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utf8 before calling the C<execute> method. |
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|
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Examples: |
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|
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# easy one |
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my $st = sql_exec "select name, id from table where id = ?", $id; |
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while (my ($name, $id) = $st->fetchrow_array) { ... }; |
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|
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# the fastest way to use dbi, using bind_columns |
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my $st = sql_exec \my($name, $id), |
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"select name, id from table where id = ?", |
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$id; |
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while ($st->fetch) { ...} |
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|
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# now use a different dastabase: |
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sql_exec $dbh, "update file set name = ?", "oops.txt"; |
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|
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|
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=item sql_fetch <see sql_exec> |
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|
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=item sql_ufetch <see sql_uexec> |
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|
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Execute an sql-statement and fetch the first row of results. Depending on |
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the caller context the row will be returned as a list (array context), or |
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just the first columns. In table form: |
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|
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CONTEXT RESULT |
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void () |
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scalar first column |
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list array |
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|
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C<sql_fetch> is quite efficient in conjunction with bind variables: |
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|
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sql_fetch \my($name, $amount), |
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"select name, amount from table where id name = ?", |
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"Toytest"; |
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|
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But of course the normal way to call it is simply: |
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|
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my($name, $amount) = sql_fetch "select ...", args... |
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|
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... and it's still quite fast unless you fetch large amounts of data. |
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|
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C<sql_ufetch> is similar to C<sql_fetch> but upgrades all input values to |
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utf8 and forces all result values to utf8. |
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|
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=item sql_fetchall <see sql_exec> |
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|
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=item sql_ufetchall <see sql_uexec> |
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|
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Similarly to C<sql_fetch>, but all result rows will be fetched (this is |
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of course inefficient for large results!). The context is ignored (only |
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list context makes sense), but the result still depends on the number of |
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columns in the result: |
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|
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COLUMNS RESULT |
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0 () |
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1 (row1, row2, row3...) |
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many ([row1], [row2], [row3]...) |
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|
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Examples (all of which are inefficient): |
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|
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for (sql_fetchall "select id from table") { ... } |
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|
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my @names = sql_fetchall "select name from user"; |
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|
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for (sql_fetchall "select name, age, place from user") { |
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my ($name, $age, $place) = @$_; |
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} |
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|
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C<sql_ufetchall> is similar to C<sql_fetchall> but upgrades all input |
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values to utf8 and forces all result values to utf8. |
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|
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=item sql_exists "<table> where ...", args... |
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|
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=item sql_uexists <see sql_exists> |
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|
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Check wether the result of the sql-statement "select xxx from |
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$first_argument" would be empty or not (that is, imagine the string |
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"select * from" were prepended to your statement (it isn't)). Should work |
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with every database but can be quite slow, except on mysql, where this |
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should be quite fast. |
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|
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C<sql_uexists> is similar to C<sql_exists> but upgrades all parameters to |
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utf8. |
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|
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Examples: |
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|
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print "user 7 exists!\n" |
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if sql_exists "user where id = ?", 7; |
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|
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die "duplicate key" |
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if sql_exists "user where name = ? and pass = ?", "stefan", "geheim"; |
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|
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=cut |
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|
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=item $lastid = sql_insertid $sth |
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|
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Returns the last automatically created key value. It must be executed |
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directly after executing the insert statement that created it. This is |
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what is actually returned for various databases. If your database is |
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missing, please send me an e-mail on how to implement this ;) |
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|
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mysql: first C<AUTO_INCREMENT> column set to NULL |
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postgres: C<oid> column (is there a way to get the last SERIAL?) |
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sybase: C<IDENTITY> column of the last insert (slow) |
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informix: C<SERIAL> or C<SERIAL8> column of the last insert |
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|
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Except for sybase, this does not require a server access. |
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|
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=cut |
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|
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sub sql_insertid($) { |
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my $sth = shift or die "sql_insertid requires a statement handle"; |
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my $dbh = $sth->{Database}; |
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my $driver = $dbh->{Driver}{Name}; |
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|
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$driver eq "mysql" and return $sth->{mysql_insertid}; |
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$driver eq "Pg" and return $sth->{pg_oid_status}; |
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$driver eq "Sybase" and return sql_fetch($dbh, 'SELECT @@IDENTITY'); |
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$driver eq "Informix" and return $sth->{ix_sqlerrd}[1]; |
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|
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die "sql_insertid does not spport the dbd driver '$driver', please see PApp::SQL::sql_insertid"; |
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} |
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|
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=item [old-size] = cachesize [new-size] |
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|
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Returns (and possibly changes) the LRU cache size used by C<sql_exec>. The |
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default is somewhere around 50 (= the 50 last recently used statements |
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will be cached). It shouldn't be too large, since a simple linear listed |
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is used for the cache at the moment (which, for small (<100) cache sizes |
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is actually quite fast). |
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|
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The function always returns the cache size in effect I<before> the call, |
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so, to nuke the cache (for example, when a database connection has died |
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or you want to garbage collect old database/statement handles), this |
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construct can be used: |
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|
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PApp::SQL::cachesize PApp::SQL::cachesize 0; |
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|
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=cut |
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|
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=item reinitialize [not exported] |
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|
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Clears any internal caches (statement cache, database handle |
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cache). Should be called after C<fork> and other accidents that invalidate |
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database handles. |
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|
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=cut |
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|
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sub reinitialize { |
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cachesize cachesize 0; |
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for (values %dbcache) { |
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eval { $_->{InactiveDestroy} = 1 }; |
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} |
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undef %dbcache; |
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} |
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|
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=back |
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|
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=cut |
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|
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reinitialize; |
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|
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package PApp::SQL::Database; |
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|
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=head2 THE DATABASE CLASS |
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|
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Again (sigh) the problem of persistency. What do you do when you have |
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to serialize on object that contains (or should contain) a database |
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handle? Short answer: you don't. Long answer: you can embed the necessary |
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information to recreate the dbh when needed. |
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|
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The C<PApp::SQL::Database> class does that, in a relatively efficient |
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fashion: the overhead is currently a single method call per access (you |
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can cache the real dbh if you want). |
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|
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=over 4 |
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|
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=item $db = new <same arguments as C<connect_cached>> |
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|
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The C<new> call takes the same arguments as C<connect_cached> (obviously, |
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if you supply a connect callback it better is serializable, see |
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L<PApp::Callback>!) and returns a serializable database class. No database |
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handle is actually being created. |
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|
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=item $db->dbh |
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|
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Return the database handle as fast as possible (usually just a hash lookup). |
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|
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=item $db->checked_dbh |
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|
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Return the database handle, but first check that the database is still |
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available and re-open the connection if necessary. |
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|
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=cut |
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|
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sub new($$;@) { |
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my $class = shift; |
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my ($id, $dsn, $user, $pass, $flags, $connect) = @_; |
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# the following line is duplicated in PApp::SQL::Database::new |
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my $id2 = "$id\0$dsn\0$user\0$pass"; |
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bless [$id2, $flags, $connect], $class; |
| 376 |
} |
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|
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# the following two functions better be fast! |
| 379 |
sub dbh($) { |
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$dbcache{$_[0][0]} || $_[0]->checked_dbh; |
| 381 |
} |
| 382 |
|
| 383 |
sub checked_dbh($) { |
| 384 |
my $dbh = $dbcache{$_[0][0]}; |
| 385 |
$dbh && $dbh->ping |
| 386 |
? $dbh |
| 387 |
: PApp::SQL::connect_cached((split /\x00/, $_[0][0]), $_[0][1], $_[0][2]); |
| 388 |
} |
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|
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=item $db->dsn |
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|
| 392 |
Return the DSN (L<DBI>) fo the database object (e.g. for error messages). |
| 393 |
|
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=item $db->login |
| 395 |
|
| 396 |
Return the login name. |
| 397 |
|
| 398 |
=item $db->password |
| 399 |
|
| 400 |
Return the password (emphasizing the fact that the apssword is stored plaintext ;) |
| 401 |
|
| 402 |
=cut |
| 403 |
|
| 404 |
sub dsn($) { |
| 405 |
my $self = shift; |
| 406 |
(split /\x00/, $self->[0])[1]; |
| 407 |
} |
| 408 |
|
| 409 |
sub login($) { |
| 410 |
my $self = shift; |
| 411 |
(split /\x00/, $self->[0])[2]; |
| 412 |
} |
| 413 |
|
| 414 |
sub password($) { |
| 415 |
my $self = shift; |
| 416 |
(split /\x00/, $self->[0])[3]; |
| 417 |
} |
| 418 |
|
| 419 |
=back |
| 420 |
|
| 421 |
=cut |
| 422 |
|
| 423 |
1; |
| 424 |
|
| 425 |
=head1 SEE ALSO |
| 426 |
|
| 427 |
L<PApp>. |
| 428 |
|
| 429 |
=head1 AUTHOR |
| 430 |
|
| 431 |
Marc Lehmann <pcg@goof.com> |
| 432 |
http://www.goof.com/pcg/marc/ |
| 433 |
|
| 434 |
=cut |
| 435 |
|
