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Documentation of the system catalogs, directed toward PostgreSQL developers

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<chapter id="catalogs">

<entry>relhasindex</entry>

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

<entry></entry>

<entry>True if this is a table and it has (or recently had) any indexes.

This is set by CREATE INDEX, but not cleared immediately by DROP INDEX.

VACUUM clears relhasindex if it finds the table has no indexes.

<entry>

True if this is a table and it has (or recently had) any

indexes. This is set by <command>CREATE INDEX</command>, but

not cleared immediately by <command>DROP INDEX</command>.

<command>VACUUM</command> clears relhasindex if it finds the

table has no indexes.

</entry>

</row>

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

<entry></entry>

<entry>

This is false for internal languages (such as SQL) and true for

user-defined languages. Currently,

<application>pg_dump</application> still uses this to determine

which languages need to be dumped, but this may be replaced by

a different mechanism sometime.

This is false for internal languages (such as

<acronym>SQL</acronym>) and true foruser-defined languages.

Currently,<application>pg_dump</application> still uses this

to determinewhich languages need to be dumped, but this may be

replaced bya different mechanism sometime.

</entry>

</row>

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PostgreSQL documentation

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<date>2000-03-25</date>

</refsynopsisdivinfo>

<synopsis>

CREATE TRIGGER <replaceable class="PARAMETER">name</replaceable> {

BEFORE | AFTER } { <replaceable class="PARAMETER">event</replaceable> [ OR ... ] }

ON <replaceable class="PARAMETER">table</replaceable> [ FOR EACH { ROW | STATEMENT } ]

CREATE TRIGGER <replaceable class="PARAMETER">name</replaceable> { BEFORE | AFTER } { <replaceable class="PARAMETER">event</replaceable> [ OR ... ] }

ON <replaceable class="PARAMETER">table</replaceable> [ FOR [ EACH ] { ROW | STATEMENT } ]

EXECUTE PROCEDURE <replaceable class="PARAMETER">func</replaceable> ( <replaceable class="PARAMETER">arguments</replaceable> )

</synopsis>

deleted tuple. In contrast, a trigger that executes <literal>FOR

EACH STATEMENT</literal> of the specified operation only executes

once for any given operation, regardless of how many rows it

modifies.

modifies (in particular, an operation that modifies zero rows will

still result in the execution of any applicable <literal>FOR EACH

STATEMENT</literal> triggers).

</para>

<para>

time-of-creation order. <productname>PostgreSQL</productname>

uses name order, which was judged more convenient to work with.

</para>

<para>

The ability to specify multiple actions for a single trigger

using <literal>OR</literal> is a <productname>PostgreSQL</>

extension of the SQL standard.

</para>

</listitem>

</varlistentry>

</variablelist>