<!--
doc/src/sgml/ref/drop_index.sgml
PostgreSQL documentation
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<refentry id="SQL-DROPINDEX">
 <refmeta>
  <refentrytitle>DROP INDEX</refentrytitle>
  <manvolnum>7</manvolnum>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>DROP INDEX</refname>
  <refpurpose>remove an index</refpurpose>
 </refnamediv>

 <indexterm zone="sql-dropindex">
  <primary>DROP INDEX</primary>
 </indexterm>

 <refsynopsisdiv>
<synopsis>
DROP INDEX [ CONCURRENTLY ] [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>DROP INDEX</command> drops an existing index from the database
   system. To execute this command you must be the owner of
   the index.
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

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

   <varlistentry>
    <term><literal>CONCURRENTLY</literal></term>
    <listitem>
     <para>
      When this option is used, <productname>PostgreSQL</> will drop the
      index without taking any locks that prevent concurrent selects, inserts,
      updates, or deletes on the table; whereas a standard index drop
      waits for a lock that locks out everything on the table until it's done.
      Concurrent drop index is a two stage process. First, we mark the index
      both invalid and not ready then commit the change. Next we wait until
      there are no users locking the table who can see the index.
     </para>
     <para>
      There are several caveats to be aware of when using this option.
      Only one index name can be specified if the <literal>CONCURRENTLY</literal>
      parameter is specified.  Regular <command>DROP INDEX</> command can be
      performed within a transaction block, but
      <command>DROP INDEX CONCURRENTLY</> cannot.
      The CASCADE option is not supported when dropping an index concurrently.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="PARAMETER">name</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of an index to remove.
     </para>
    </listitem>
   </varlistentry>

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

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

 <refsect1>
  <title>Examples</title>

  <para>
   This command will remove the index <literal>title_idx</literal>:

<programlisting>
DROP INDEX title_idx;
</programlisting></para>
 </refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   <command>DROP INDEX</command> is a
   <productname>PostgreSQL</productname> language extension.  There
   are no provisions for indexes in the SQL standard.
  </para>
 </refsect1>

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

  <simplelist type="inline">
   <member><xref linkend="sql-createindex"></member>
  </simplelist>
 </refsect1>

</refentry>
