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<chapter id="catalogs">

<entry><structfield>tgenabled</structfield></entry>

<entry><type>bool</type></entry>

<entry></entry>

<entry>True if trigger is enabled (not presently checked everywhere

it should be, so disabling a trigger by setting this false does not

work reliably)</entry>

<entry>True if trigger is enabled</entry>

</row>

<row>

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ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }

ADD <replaceable class="PARAMETER">table_constraint</replaceable>

DROP CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> [ RESTRICT | CASCADE ]

DISABLE TRIGGER [ <replaceable class="PARAMETER">trigger_name</replaceable> | ALL | USER ]

ENABLE TRIGGER [ <replaceable class="PARAMETER">trigger_name</replaceable> | ALL | USER ]

CLUSTER ON <replaceable class="PARAMETER">index_name</replaceable>

SET WITHOUT CLUSTER

SET WITHOUT OIDS

</listitem>

</varlistentry>

<varlistentry>

<term><literal>DISABLE</literal>/<literal>ENABLE TRIGGER</literal></term>

<listitem>

<para>

These forms disable or enable trigger(s) belonging to the table.

A disabled trigger is still known to the system, but is not executed

when its triggering event occurs. For a deferred trigger, the enable

status is checked when the event occurs, not when the trigger function

is actually executed. One may disable or enable a single

trigger specified by name, or all triggers on the table, or only

user triggers (this option excludes triggers that are used to implement

foreign key constraints). Disabling or enabling constraint triggers

requires superuser privileges; it should be done with caution since

of course the integrity of the constraint cannot be guaranteed if the

triggers are not executed.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><literal>CLUSTER</literal></term>

<listitem>

You must own the table to use <command>ALTER TABLE</>.

To change the schema of a table, you must also have

<literal>CREATE</literal> privilege on the new schema.

To alter the owner, the new owner must have

<literal>CREATE</literal> privilege on the schema.

To alter the owner, you must also be a direct or indirect member of the new

owning role, and that role must have <literal>CREATE</literal> privilege on

the table's schema. (These restrictions enforce that altering the owner

doesn't do anything you couldn't do by dropping and recreating the table.

However, a superuser can alter ownership of any table anyway.)

</para>

</refsect1>

</listitem>

</varlistentry>

<varlistentry>

<term><replaceable class="PARAMETER">trigger_name</replaceable></term>

<listitem>

<para>

Name of a single trigger to disable or enable.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><literal>ALL</literal></term>

<listitem>

<para>

Disable or enable all triggers belonging to the table.

(This requires superuser privilege if any of the triggers are for

foreign key constraints.)

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><literal>USER</literal></term>

<listitem>

<para>

Disable or enable all triggers belonging to the table except for

foreign key constraint triggers.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><replaceable class="PARAMETER">index_name</replaceable></term>

<listitem>

instead marks them as independently defined rather than inherited.

</para>

<para>

The <literal>TRIGGER</>, <literal>CLUSTER</>, <literal>OWNER</>,

and <literal>TABLESPACE</> actions never recurse to descendant tables;

that is, they always act as though <literal>ONLY</> were specified.

Adding a constraint can recurse only for <literal>CHECK</> constraints.

</para>

<para>

Changing any part of a system catalog table is not permitted.

</para>

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</variablelist>

</refsect1>

<refsect1>

<title>Notes</title>

<para>

The ability to temporarily enable or disable a trigger is provided by

<xref linkend="SQL-ALTERTABLE" endterm="SQL-ALTERTABLE-TITLE">, not by

<command>ALTER TRIGGER</>, because <command>ALTER TRIGGER</> has no

convenient way to express the option of enabling or disabling all of

a table's triggers at once.

</para>

</refsect1>

<refsect1>

<title>Examples</title>

extension of the SQL standard.

</para>

</refsect1>

<refsect1>

<title>See Also</title>

<simplelist type="inline">

<member><xref linkend="sql-altertable" endterm="sql-altertable-title"></member>

</simplelist>

</refsect1>

</refentry>

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