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<div id="page-content"><div id="preamble"><h1>Apache模块 mod_dbd</h1>
<table border="1" cellpadding="0" cellspacing="0" bordercolor="#AAAAAA" class="module">
<tr><th><a href="module-dict.html#Description">说明</a></th><td>管理SQL数据库连接，为需要数据库功能的模块提供支持</td></tr>
<tr><th><a href="module-dict.html#Status">状态</a></th><td>扩展(E)</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">模块名</a></th><td>dbd_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">源文件</a></th><td>mod_dbd.c</td></tr>
<tr><th><a href="module-dict.html#Compatibility">兼容性</a></th><td>Version 2.1 及以后的版本中可用</td></tr>
</table>
<h3>概述</h3>
<p><code class="module"><a href="../mod/mod_dbd.html">mod_dbd</a></code> manages SQL database connections using
<a href="http://people.apache.org/~niq/dbd.html">apr_dbd</a>.
It provides database connections on request to modules
requiring SQL database functions, and takes care of
managing databases with optimal efficiency and scalability
for both threaded and non-threaded MPMs.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="pooling" id="pooling">Connection Pooling</a></h2>
<p>This module manages database connections, in a manner
optimised for the platform. On non-threaded platforms,
it provides a persistent connection in the manner of
classic LAMP (Linux, Apache, Mysql, Perl/PHP/Python).
On threaded platform, it provides an altogether more
scalable and efficient <em>connection pool</em>, as
described in <a href="http://www.apachetutor.org/dev/reslist">this article at ApacheTutor</a>. <code class="module"><a href="../mod/mod_dbd.html">mod_dbd</a></code> supersedes
the modules presented in that article.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="API" id="API">Apache DBD API</a></h2>
<p><code class="module"><a href="../mod/mod_dbd.html">mod_dbd</a></code> exports five functions for other modules
to use. The API is as follows:</p>
<div class="example"><pre><code>typedef struct {
apr_dbd_t *handle;
apr_dbd_driver_t *driver;
apr_hash_t *prepared;
} ap_dbd_t;
/* Export functions to access the database */
/* acquire a connection that MUST be explicitly closed.
* Returns NULL on error
*/
AP_DECLARE(ap_dbd_t*) ap_dbd_open(apr_pool_t*, server_rec*);
/* release a connection acquired with ap_dbd_open */
AP_DECLARE(void) ap_dbd_close(server_rec*, ap_dbd_t*);
/* acquire a connection that will have the lifetime of a request
* and MUST NOT be explicitly closed. Return NULL on error.
* This is the preferred function for most applications.
*/
AP_DECLARE(ap_dbd_t*) ap_dbd_acquire(request_rec*);
/* acquire a connection that will have the lifetime of a connection
* and MUST NOT be explicitly closed. Return NULL on error.
*/
AP_DECLARE(ap_dbd_t*) ap_dbd_cacquire(request_rec*);
/* Prepare a statement for use by a client module */
AP_DECLARE(void) ap_dbd_prepare(server_rec*, const char*, const char*);
/* Also export them as optional functions for modules that prefer it */
APR_DECLARE_OPTIONAL_FN(ap_dbd_t*, ap_dbd_open, (apr_pool_t*, server_rec*));
APR_DECLARE_OPTIONAL_FN(void, ap_dbd_close, (server_rec*, ap_dbd_t*));
APR_DECLARE_OPTIONAL_FN(ap_dbd_t*, ap_dbd_acquire, (request_rec*));
APR_DECLARE_OPTIONAL_FN(ap_dbd_t*, ap_dbd_cacquire, (conn_rec*));
APR_DECLARE_OPTIONAL_FN(void, ap_dbd_prepare, (server_rec*, const char*, const char*));
</code></pre></div>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="prepared" id="prepared">SQL Prepared Statements</a></h2>
<p><code class="module"><a href="../mod/mod_dbd.html">mod_dbd</a></code> supports SQL prepared statements on behalf
of modules that may wish to use them. Each prepared statement
must be assigned a name (label), and they are stored in a hash:
the <code>prepared</code> field of an <code>ap_dbd_t</code>.
Hash entries are of type <code>apr_dbd_prepared_t</code>
and can be used in any of the apr_dbd prepared statement
SQL query or select commands.</p>
<p>It is up to dbd user modules to use the prepared statements
and document what statements can be specified in httpd.conf,
or to provide their own directives and use <code>ap_dbd_prepare</code>.</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="DBDExptime" id="DBDExptime">DBDExptime</a> <a name="dbdexptime" id="dbdexptime">指令</a></h2>
<table border="1" cellpadding="0" cellspacing="0" bordercolor="#AAAAAA" class="directive">
<tr><th><a href="directive-dict.html#Description">说明</a></th><td>Keepalive time for idle connections</td></tr>
<tr><th><a href="directive-dict.html#Syntax">语法</a></th><td><code>DBDExptime <var>time-in-seconds</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">作用域</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">状态</a></th><td>扩展(E)</td></tr>
<tr><th><a href="directive-dict.html#Module">模块</a></th><td>mod_dbd</td></tr>
</table>
<p>Set the time to keep idle connections alive where the number
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