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<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
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XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
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This file is generated from xml source: DO NOT EDIT
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XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
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-->
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<title>mod_dbd - Apache HTTP Server</title>
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<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
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<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
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<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
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<link href="../images/favicon.ico" rel="shortcut icon" /></head>
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<body>
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<div id="page-header">
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<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
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<p class="apache">Apache HTTP Server Version 2.3</p>
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<img alt="" src="../images/feather.gif" /></div>
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<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
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<div id="path">
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.3</a> > <a href="./">Modules</a></div>
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<div id="page-content">
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<div id="preamble"><h1>Apache Module mod_dbd</h1>
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<div class="toplang">
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<p><span>Available Languages: </span><a href="../en/mod/mod_dbd.html" title="English"> en </a></p>
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</div>
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Manages SQL database connections</td></tr>
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<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="module-dict.html#ModuleIdentifier">Module<EFBFBD>Identifier:</a></th><td>dbd_module</td></tr>
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<tr><th><a href="module-dict.html#SourceFile">Source<EFBFBD>File:</a></th><td>mod_dbd.c</td></tr>
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<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Version 2.1 and later</td></tr></table>
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<h3>Summary</h3>
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<p><code class="module"><a href="../mod/mod_dbd.html">mod_dbd</a></code> manages SQL database connections using
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<a class="glossarylink" href="../glossary.html#apr" title="see glossary">APR</a>. It provides database connections on request
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to modules requiring SQL database functions, and takes care of
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managing databases with optimal efficiency and scalability
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for both threaded and non-threaded MPMs. For details, see the
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<a href="http://apr.apache.org/">APR</a> website and this overview of the
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<a href="http://people.apache.org/~niq/dbd.html">Apache DBD Framework</a>
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by its original developer.
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</p>
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</div>
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<div id="quickview"><h3 class="directives">Directives</h3>
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<ul id="toc">
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<li><img alt="" src="../images/down.gif" /> <a href="#dbdexptime">DBDExptime</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#dbdkeep">DBDKeep</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#dbdmax">DBDMax</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#dbdmin">DBDMin</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#dbdparams">DBDParams</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#dbdpersist">DBDPersist</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#dbdpreparesql">DBDPrepareSQL</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#dbdriver">DBDriver</a></li>
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</ul>
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<h3>Topics</h3>
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<ul id="topics">
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<li><img alt="" src="../images/down.gif" /> <a href="#pooling">Connection Pooling</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#API">Apache DBD API</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#prepared">SQL Prepared Statements</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#security">SECURITY WARNING</a></li>
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</ul><h3>See also</h3>
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<ul class="seealso">
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<li><a href="../misc/password_encryptions.html">Password Formats</a></li>
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</ul></div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="pooling" id="pooling">Connection Pooling</a></h2>
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<p>This module manages database connections, in a manner
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optimised for the platform. On non-threaded platforms,
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||
it provides a persistent connection in the manner of
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classic LAMP (Linux, Apache, Mysql, Perl/PHP/Python).
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||
On threaded platform, it provides an altogether more
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||
scalable and efficient <em>connection pool</em>, as
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||
described in <a href="http://www.apachetutor.org/dev/reslist">this
|
||
article at ApacheTutor</a>. Note that <code class="module"><a href="../mod/mod_dbd.html">mod_dbd</a></code>
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||
supersedes the modules presented in that article.</p>
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||
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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||
<div class="section">
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||
<h2><a name="API" id="API">Apache DBD API</a></h2>
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<p><code class="module"><a href="../mod/mod_dbd.html">mod_dbd</a></code> exports five functions for other modules
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to use. The API is as follows:</p>
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<div class="example"><pre><code>typedef struct {
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apr_dbd_t *handle;
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apr_dbd_driver_t *driver;
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apr_hash_t *prepared;
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} ap_dbd_t;
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/* Export functions to access the database */
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/* acquire a connection that MUST be explicitly closed.
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* Returns NULL on error
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*/
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AP_DECLARE(ap_dbd_t*) ap_dbd_open(apr_pool_t*, server_rec*);
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/* release a connection acquired with ap_dbd_open */
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AP_DECLARE(void) ap_dbd_close(server_rec*, ap_dbd_t*);
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/* acquire a connection that will have the lifetime of a request
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* and MUST NOT be explicitly closed. Return NULL on error.
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* This is the preferred function for most applications.
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*/
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AP_DECLARE(ap_dbd_t*) ap_dbd_acquire(request_rec*);
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/* acquire a connection that will have the lifetime of a connection
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* and MUST NOT be explicitly closed. Return NULL on error.
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*/
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AP_DECLARE(ap_dbd_t*) ap_dbd_cacquire(request_rec*);
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/* Prepare a statement for use by a client module */
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AP_DECLARE(void) ap_dbd_prepare(server_rec*, const char*, const char*);
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/* Also export them as optional functions for modules that prefer it */
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APR_DECLARE_OPTIONAL_FN(ap_dbd_t*, ap_dbd_open, (apr_pool_t*, server_rec*));
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APR_DECLARE_OPTIONAL_FN(void, ap_dbd_close, (server_rec*, ap_dbd_t*));
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APR_DECLARE_OPTIONAL_FN(ap_dbd_t*, ap_dbd_acquire, (request_rec*));
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APR_DECLARE_OPTIONAL_FN(ap_dbd_t*, ap_dbd_cacquire, (conn_rec*));
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APR_DECLARE_OPTIONAL_FN(void, ap_dbd_prepare, (server_rec*, const char*, const char*));
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</code></pre></div>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="prepared" id="prepared">SQL Prepared Statements</a></h2>
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<p><code class="module"><a href="../mod/mod_dbd.html">mod_dbd</a></code> supports SQL prepared statements on behalf
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of modules that may wish to use them. Each prepared statement
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must be assigned a name (label), and they are stored in a hash:
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the <code>prepared</code> field of an <code>ap_dbd_t</code>.
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Hash entries are of type <code>apr_dbd_prepared_t</code>
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and can be used in any of the apr_dbd prepared statement
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SQL query or select commands.</p>
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<p>It is up to dbd user modules to use the prepared statements
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and document what statements can be specified in httpd.conf,
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or to provide their own directives and use <code>ap_dbd_prepare</code>.</p>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="security" id="security">SECURITY WARNING</a></h2>
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<p>Any web/database application needs to secure itself against SQL
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injection attacks. In most cases, Apache DBD is safe, because
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applications use prepared statements, and untrusted inputs are
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only ever used as data. Of course, if you use it via third-party
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modules, you should ascertain what precautions they may require.</p>
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<p>However, the <var>FreeTDS</var> driver is inherently
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<strong>unsafe</strong>. The underlying library doesn't support
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prepared statements, so the driver emulates them, and the
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untrusted input is merged into the SQL statement.</p>
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<p>It can be made safe by <em>untainting</em> all inputs:
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a process inspired by Perl's taint checking. Each input
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is matched against a regexp, and only the match is used,
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according to the Perl idiom:</p>
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<div class="example"><pre><code> $untrusted =~ /([a-z]+)/;
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$trusted = $1;</code></pre></div>
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<p>To use this, the untainting regexps must be included in the
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prepared statements configured. The regexp follows immediately
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after the % in the prepared statement, and is enclosed in
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curly brackets {}. For example, if your application expects
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alphanumeric input, you can use:</p>
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<div class="example"><p><code>
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<code>"SELECT foo FROM bar WHERE input = %s"</code>
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</code></p></div>
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<p>with other drivers, and suffer nothing worse than a failed query.
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But with FreeTDS you'd need:</p>
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<div class="example"><p><code>
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<code>"SELECT foo FROM bar WHERE input = %{([A-Za-z0-9]+)}s"</code>
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</code></p></div>
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<p>Now anything that doesn't match the regexp's $1 match is
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discarded, so the statement is safe.</p>
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<p>An alternative to this may be the third-party ODBC driver,
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which offers the security of genuine prepared statements.</p>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="DBDExptime" id="DBDExptime">DBDExptime</a> <a name="dbdexptime" id="dbdexptime">Directive</a></h2>
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||
<table class="directive">
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||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Keepalive time for idle connections</td></tr>
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||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DBDExptime <var>time-in-seconds</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DBDExptime 300</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
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||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_dbd</td></tr>
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||
</table>
|
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<p>Set the time to keep idle connections alive when the number
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of connections specified in DBDKeep has been exceeded (threaded
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platforms only).</p>
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||
</div>
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||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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||
<div class="directive-section"><h2><a name="DBDKeep" id="DBDKeep">DBDKeep</a> <a name="dbdkeep" id="dbdkeep">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum sustained number of connections</td></tr>
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||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DBDKeep <var>number</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DBDKeep 2</code></td></tr>
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||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
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||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_dbd</td></tr>
|
||
</table>
|
||
<p>Set the maximum number of connections per process to be
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sustained, other than for handling peak demand (threaded
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platforms only).</p>
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||
</div>
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||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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||
<div class="directive-section"><h2><a name="DBDMax" id="DBDMax">DBDMax</a> <a name="dbdmax" id="dbdmax">Directive</a></h2>
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||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of connections</td></tr>
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||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DBDMax <var>number</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DBDMax 10</code></td></tr>
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||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
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||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_dbd</td></tr>
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</table>
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<p>Set the hard maximum number of connections per process
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(threaded platforms only).</p>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="DBDMin" id="DBDMin">DBDMin</a> <a name="dbdmin" id="dbdmin">Directive</a></h2>
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<table class="directive">
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||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of connections</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DBDMin <var>number</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DBDMin 1</code></td></tr>
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||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
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||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_dbd</td></tr>
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||
</table>
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||
<p>Set the minimum number of connections per process (threaded
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platforms only).</p>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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||
<div class="directive-section"><h2><a name="DBDParams" id="DBDParams">DBDParams</a> <a name="dbdparams" id="dbdparams">Directive</a></h2>
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||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Parameters for database connection</td></tr>
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||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DBDParams
|
||
<var>param1</var>=<var>value1</var>[,<var>param2</var>=<var>value2</var>]</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_dbd</td></tr>
|
||
</table>
|
||
<p>As required by the underlying driver. Typically this will be
|
||
used to pass whatever cannot be defaulted amongst username,
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password, database name, hostname and port number for connection.</p>
|
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<p>Connection string parameters for current drivers include:</p>
|
||
<dl>
|
||
<dt>FreeTDS (for MSSQL and SyBase)</dt>
|
||
<dd>username, password, appname, dbname, host, charset, lang, server</dd>
|
||
<dt>MySQL</dt>
|
||
<dd>host, port, user, pass, dbname, sock, flags, fldsz, group, reconnect</dd>
|
||
<dt>Oracle</dt>
|
||
<dd>user, pass, dbname, server</dd>
|
||
<dt>PostgreSQL</dt>
|
||
<dd>The connection string is passed straight through to <code>PQconnectdb</code></dd>
|
||
<dt>SQLite2</dt>
|
||
<dd>The connection string is split on a colon, and <code>part1:part2</code> is used as <code>sqlite_open(part1, atoi(part2), NULL)</code></dd>
|
||
<dt>SQLite3</dt>
|
||
<dd>The connection string is passed straight through to <code>sqlite3_open</code></dd>
|
||
<dt>ODBC</dt>
|
||
<dd>datasource, user, password, connect, ctimeout, stimeout, access, txmode, bufsize</dd>
|
||
</dl>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="DBDPersist" id="DBDPersist">DBDPersist</a> <a name="dbdpersist" id="dbdpersist">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Whether to use persistent connections</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DBDPersist On|Off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_dbd</td></tr>
|
||
</table>
|
||
<p>If set to Off, persistent and pooled connections are disabled.
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A new database connection is opened when requested by a client,
|
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and closed immediately on release. This option is for debugging
|
||
and low-usage servers.</p>
|
||
|
||
<p>The default is to enable a pool of persistent connections
|
||
(or a single LAMP-style persistent connection in the case of a
|
||
non-threaded server), and should almost always be used in operation.</p>
|
||
|
||
<p>Prior to version 2.2.2, this directive accepted only the values
|
||
<code>0</code> and <code>1</code> instead of <code>Off</code> and
|
||
<code>On</code>, respectively.</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="DBDPrepareSQL" id="DBDPrepareSQL">DBDPrepareSQL</a> <a name="dbdpreparesql" id="dbdpreparesql">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Define an SQL prepared statement</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DBDPrepareSQL <var>"SQL statement"</var> <var>label</var></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_dbd</td></tr>
|
||
</table>
|
||
<p>For modules such as authentication that repeatedly use a
|
||
single SQL statement, optimum performance is achieved by preparing
|
||
the statement at startup rather than every time it is used.
|
||
This directive prepares an SQL statement and assigns it a label.</p>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="DBDriver" id="DBDriver">DBDriver</a> <a name="dbdriver" id="dbdriver">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify an SQL driver</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DBDriver <var>name</var></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_dbd</td></tr>
|
||
</table>
|
||
<p>Selects an apr_dbd driver by name. The driver must be installed
|
||
on your system (on most systems, it will be a shared object or dll).
|
||
For example, <code>DBDriver mysql</code> will select the MySQL
|
||
driver in apr_dbd_mysql.so.</p>
|
||
|
||
</div>
|
||
</div>
|
||
<div class="bottomlang">
|
||
<p><span>Available Languages: </span><a href="../en/mod/mod_dbd.html" title="English"> en </a></p>
|
||
</div><div id="footer">
|
||
<p class="apache">Copyright 2010 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
|
||
<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
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