141 lines
3.7 KiB
Plaintext
141 lines
3.7 KiB
Plaintext
<!--
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doc/src/sgml/ref/drop_index.sgml
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PostgreSQL documentation
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-->
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<refentry id="sql-dropindex">
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<indexterm zone="sql-dropindex">
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<primary>DROP INDEX</primary>
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</indexterm>
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<refmeta>
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<refentrytitle>DROP INDEX</refentrytitle>
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<manvolnum>7</manvolnum>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>DROP INDEX</refname>
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<refpurpose>remove an index</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<synopsis>
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DROP INDEX [ CONCURRENTLY ] [ IF EXISTS ] <replaceable class="parameter">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
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</synopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<command>DROP INDEX</command> drops an existing index from the database
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system. To execute this command you must be the owner of
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the index.
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</para>
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</refsect1>
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<refsect1>
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<title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><literal>CONCURRENTLY</literal></term>
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<listitem>
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<para>
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Drop the index without locking out concurrent selects, inserts, updates,
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and deletes on the index's table. A normal <command>DROP INDEX</command>
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acquires exclusive lock on the table, blocking other accesses until the
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index drop can be completed. With this option, the command instead
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waits until conflicting transactions have completed.
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</para>
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<para>
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There are several caveats to be aware of when using this option.
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Only one index name can be specified, and the <literal>CASCADE</literal> option
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is not supported. (Thus, an index that supports a <literal>UNIQUE</literal> or
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<literal>PRIMARY KEY</literal> constraint cannot be dropped this way.)
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Also, regular <command>DROP INDEX</command> commands can be
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performed within a transaction block, but
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<command>DROP INDEX CONCURRENTLY</command> cannot.
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</para>
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<para>
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For temporary tables, <command>DROP INDEX</command> is always
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non-concurrent, as no other session can access them, and
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non-concurrent index drop is cheaper.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>IF EXISTS</literal></term>
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<listitem>
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<para>
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Do not throw an error if the index does not exist. A notice is issued
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in this case.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">name</replaceable></term>
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<listitem>
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<para>
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The name (optionally schema-qualified) of an index to remove.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>CASCADE</literal></term>
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<listitem>
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<para>
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Automatically drop objects that depend on the index,
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and in turn all objects that depend on those objects
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(see <xref linkend="ddl-depend"/>).
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>RESTRICT</literal></term>
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<listitem>
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<para>
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Refuse to drop the index if any objects depend on it. This is
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the default.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<para>
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This command will remove the index <literal>title_idx</literal>:
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<programlisting>
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DROP INDEX title_idx;
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</programlisting></para>
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</refsect1>
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<refsect1>
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<title>Compatibility</title>
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<para>
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<command>DROP INDEX</command> is a
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<productname>PostgreSQL</productname> language extension. There
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are no provisions for indexes in the SQL standard.
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</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<simplelist type="inline">
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<member><xref linkend="sql-createindex"/></member>
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</simplelist>
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</refsect1>
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</refentry>
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