drop_opclass.sgml

postgresql8.3.4源码,开源数据库

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<refentry id="SQL-DROPOPCLASS">
 <refmeta>
  <refentrytitle id="SQL-DROPOPCLASS-TITLE">DROP OPERATOR CLASS</refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>DROP OPERATOR CLASS</refname>
  <refpurpose>remove an operator class</refpurpose>
 </refnamediv>
  
 <indexterm zone="sql-dropopclass">
  <primary>DROP OPERATOR CLASS</primary>
 </indexterm>

 <refsynopsisdiv>
<synopsis>
DROP OPERATOR CLASS [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> USING <replaceable class="PARAMETER">index_method</replaceable> [ CASCADE | RESTRICT ]
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>DROP OPERATOR CLASS</command> drops an existing operator class.
   To execute this command you must be the owner of the operator class.
  </para>

  <para>
   <command>DROP OPERATOR CLASS</command> does not drop any of the operators
   or functions referenced by the class.  If there are any indexes depending
   on the operator class, you will need to specify
   <literal>CASCADE</> for the drop to complete.
  </para>
 </refsect1>
  
 <refsect1>
  <title>Parameters</title>

  <variablelist>

   <varlistentry>
    <term><literal>IF EXISTS</literal></term>
    <listitem>
     <para>
      Do not throw an error if the operator class does not exist. A notice is issued 
      in this case.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">name</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of an existing operator class.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">index_method</replaceable></term>
    <listitem>
     <para>
      The name of the index access method the operator class is for.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>CASCADE</literal></term>
    <listitem>
     <para>
      Automatically drop objects that depend on the operator class.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>RESTRICT</literal></term>
    <listitem>
     <para>
      Refuse to drop the operator class if any objects depend on it.
      This is the default.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>
  
 <refsect1>
  <title>Notes</title>

  <para>
   <command>DROP OPERATOR CLASS</> will not drop the operator family
   containing the class, even if there is nothing else left in the
   family (in particular, in the case where the family was implicitly
   created by <command>CREATE OPERATOR CLASS</>).  An empty operator
   family is harmless, but for the sake of tidiness you might wish to
   remove the family with <command>DROP OPERATOR FAMILY</>; or perhaps
   better, use <command>DROP OPERATOR FAMILY</> in the first place.
  </para>
 </refsect1>

 <refsect1>
  <title>Examples</title>

  <para>
   Remove the B-tree operator class <literal>widget_ops</literal>:

<programlisting>
DROP OPERATOR CLASS widget_ops USING btree;
</programlisting>

   This command will not succeed if there are any existing indexes
   that use the operator class.  Add <literal>CASCADE</> to drop
   such indexes along with the operator class.
  </para>
 </refsect1>
 
 <refsect1>
  <title>Compatibility</title>

  <para>
   There is no <command>DROP OPERATOR CLASS</command> statement in the
   SQL standard.
  </para>
 </refsect1>

 <refsect1>
  <title>See Also</title>

  <simplelist type="inline">
   <member><xref linkend="sql-alteropclass" endterm="sql-alteropclass-title"></member>
   <member><xref linkend="sql-createopclass" endterm="sql-createopclass-title"></member>
   <member><xref linkend="sql-dropopfamily" endterm="sql-dropopfamily-title"></member>
  </simplelist>
 </refsect1>

</refentry>