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Some sections of the documentation used "exclusive lock" to describe that an ACCESS EXCLUSIVE lock is taken during a given operation. This can be confusing to the reader as ACCESS SHARE is allowed with an EXCLUSIVE lock is used, but that would not be the case with what is described on those parts of the documentation. Author: Greg Rychlewski Discussion: https://postgr.es/m/CAKemG7VptD=7fNWckFMsMVZL_zzvgDO6v2yVmQ+ZiBfc_06kCQ@mail.gmail.com Backpatch-through: 9.6
144 lines
3.8 KiB
Plaintext
144 lines
3.8 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 an <literal>ACCESS EXCLUSIVE</literal> lock on the table,
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blocking other accesses until the index drop can be completed. With
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this option, the command instead waits until conflicting transactions
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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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Lastly, indexes on partitioned tables cannot be dropped using this
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option.
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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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