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<!--
doc/src/sgml/ref/drop_index.sgml
PostgreSQL documentation
-->
<refentry id="sql-dropindex">
<indexterm zone="sql-dropindex">
<primary>DROP INDEX</primary>
</indexterm>
<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>
<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>CONCURRENTLY</literal></term>
<listitem>
<para>
Drop the index without locking out concurrent selects, inserts, updates,
and deletes on the index's table. A normal <command>DROP INDEX</command>
acquires an <literal>ACCESS EXCLUSIVE</literal> lock on the table,
blocking other accesses until the index drop can be completed. With
this option, the command instead waits until conflicting transactions
have completed.
</para>
<para>
There are several caveats to be aware of when using this option.
Only one index name can be specified, and the <literal>CASCADE</literal> option
is not supported. (Thus, an index that supports a <literal>UNIQUE</literal> or
<literal>PRIMARY KEY</literal> constraint cannot be dropped this way.)
Also, regular <command>DROP INDEX</command> commands can be
performed within a transaction block, but
<command>DROP INDEX CONCURRENTLY</command> cannot.
Lastly, indexes on partitioned tables cannot be dropped using this
option.
</para>
<para>
For temporary tables, <command>DROP INDEX</command> is always
non-concurrent, as no other session can access them, and
non-concurrent index drop is cheaper.
</para>
</listitem>
</varlistentry>
<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><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,
and in turn all objects that depend on those objects
(see <xref linkend="ddl-depend"/>).
</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>
|
