mirror of
https://github.com/sigmasternchen/php-doc-en
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5b7fda5490
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@318447 c90b9560-bf6c-de11-be94-00142212c4b1
246 lines
6.9 KiB
XML
Executable file
246 lines
6.9 KiB
XML
Executable file
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<appendix xml:id="mysqlnd-ms.constants" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
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&reftitle.constants;
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&extension.constants;
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<para>
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<emphasis role="bold">SQL hint related</emphasis>
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</para>
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<para>
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<example>
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<para>
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The mysqlnd replication and load balancing plugin (<literal>mysqlnd_ms</literal>)
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performs read/write splitting. This directs write queries to a MySQL
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master server, and read-only queries to the MySQL slave servers.
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The plugin has a built-in read/write split logic.
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All queries which start with <literal>SELECT</literal> are considered read-only
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queries, which are then sent to a MySQL slave server that is listed in
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the plugin configuration file. All other queries are directed to the
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MySQL master server that is also specified in the plugin configuration file.
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</para>
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<para>
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User supplied SQL hints can be used to overrule automatic read/write splitting,
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to gain full control on the process. SQL hints are standards compliant
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SQL comments. The plugin will scan the beginning of a query string for
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an SQL comment for certain commands, which then control query redirection.
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Other systems involved in the query processing are unaffected by the
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SQL hints because other systems will ignore the SQL comments.
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</para>
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<para>
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The plugin supports three SQL hints to direct queries to either the MySQL slave
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servers, the MySQL master server, or the last used MySQL server. SQL hints
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must be placed at the beginning of a query to be recognized by the plugin.
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</para>
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<para>
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For better portability, it is recommended to use the string constants
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<constant>MYSQLND_MS_MASTER_SWITCH</constant>,
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<constant>MYSQLND_MS_SLAVE_SWITCH</constant> and
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<constant>MYSQLND_MS_LAST_USED_SWITCH</constant> instead of their literal
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values.
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</para>
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<programlisting role="php">
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<![CDATA[
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<?php
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/* Use constants for maximum portability */
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$master_query = "/*" . MYSQLND_MS_MASTER_SWITCH . "*/SELECT id FROM test";
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/* Valid but less portable: using literal instead of constant */
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$slave_query = "/*ms=slave*/SHOW TABLES";
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printf("master_query = '%s'\n", $master_query);
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printf("slave_query = '%s'\n", $slave_query);
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?>
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]]>
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</programlisting>
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&examples.outputs;
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<screen>
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<![CDATA[
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master_query = /*ms=master*/SELECT id FROM test
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slave_query = /*ms=slave*/SHOW TABLES
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]]>
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</screen>
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</example>
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</para>
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<para>
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<variablelist>
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<varlistentry>
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<term>
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<constant>MYSQLND_MS_MASTER_SWITCH</constant>
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(<type>string</type>)
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</term>
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<listitem>
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<simpara>
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SQL hint used to send a query to the MySQL replication master server.
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<constant>MYSQLND_MS_SLAVE_SWITCH</constant>
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(<type>string</type>)
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</term>
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<listitem>
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<simpara>
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SQL hint used to send a query to one of the MySQL replication slave servers.
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<constant>MYSQLND_MS_LAST_USED_SWITCH</constant>
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(<type>string</type>)
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</term>
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<listitem>
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<simpara>
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SQL hint used to send a query to the last used MySQL server. The last
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used MySQL server can either be a master or a slave server in a
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MySQL replication setup.
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</simpara>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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<function>mysqlnd_ms_is_select</function> related
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</para>
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<para>
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<variablelist>
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<varlistentry>
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<term>
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<constant>MYSQLND_MS_QUERY_USE_MASTER</constant>
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(<type>integer</type>)
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</term>
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<listitem>
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<simpara>
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If <function>mysqlnd_ms_is_select</function> returns
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<constant>MYSQLND_MS_QUERY_USE_MASTER</constant> for a given query, the
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built-in read/write split mechanism recommends sending the query to
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a MySQL replication master server.
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<constant>MYSQLND_MS_QUERY_USE_SLAVE</constant>
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(<type>integer</type>)
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</term>
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<listitem>
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<simpara>
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If <function>mysqlnd_ms_is_select</function> returns
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<constant>MYSQLND_MS_QUERY_USE_SLAVE</constant> for a given query, the
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built-in read/write split mechanism recommends sending the query to
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a MySQL replication slave server.
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<constant>MYSQLND_MS_QUERY_USE_LAST_USED</constant>
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(<type>integer</type>)
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</term>
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<listitem>
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<simpara>
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If <function>mysqlnd_ms_is_select</function> returns
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<constant>MYSQLND_MS_QUERY_USE_LAST_USED</constant> for a given query, the
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built-in read/write split mechanism recommends sending the query to
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the last used server.
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</simpara>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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<emphasis role="bold">Other</emphasis>
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</para>
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<para>
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The plugins version number can be obtained using
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<constant>MYSQLND_MS_VERSION</constant> or
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<constant>MYSQLND_MS_VERSION_ID</constant>.
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<constant>MYSQLND_MS_VERSION</constant>
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is the string representation of the numerical version number
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<constant>MYSQLND_MS_VERSION_ID</constant>, which is an integer such as 10000.
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Developers can calculate the version number as follows.
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</para>
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<para>
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<informaltable>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>Version (part)</entry>
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<entry>Example</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>Major*10000</entry>
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<entry>1*10000 = 10000</entry>
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</row>
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<row>
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<entry>Minor*100</entry>
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<entry>0*100 = 0</entry>
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</row>
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<row>
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<entry>Patch</entry>
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<entry>0 = 0</entry>
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</row>
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<row>
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<entry>MYSQLND_MS_VERSION_ID</entry>
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<entry>10000</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</para>
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<para>
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<variablelist>
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<varlistentry>
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<term>
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<constant>MYSQLND_MS_VERSION</constant>
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(<type>string</type>)
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</term>
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<listitem>
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<simpara>
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Plugin version string, for example, <quote>1.0.0-prototype</quote>.
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<constant>MYSQLND_MS_VERSION_ID</constant>
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(<type>integer</type>)
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</term>
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<listitem>
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<simpara>
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Plugin version number, for example, 10000.
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</simpara>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</appendix>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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