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Generalize TRUNCATE to support truncating multiple tables in one

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command.  This is useful because we can allow truncation of tables
referenced by foreign keys, so long as the referencing table is
truncated in the same command.

Alvaro Herrera
This commit is contained in:
Tom Lane
2005-01-27 03:19:37 +00:00
parent 4fe201237f
commit f07b9689c9
14 changed files with 398 additions and 180 deletions
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29
doc/src/sgml/ref/truncate.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/truncate.sgml,v 1.17 2004/03/23 13:21:41 neilc Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/truncate.sgml,v 1.18 2005/01/27 03:17:08 tgl Exp $
PostgreSQL documentation
-->
@ -11,7 +11,7 @@ PostgreSQL documentation
<refnamediv>
<refname>TRUNCATE</refname>
<refpurpose>empty a table</refpurpose>
<refpurpose>empty a table or set of tables</refpurpose>
</refnamediv>
<indexterm zone="sql-truncate">
@ -20,7 +20,7 @@ PostgreSQL documentation
<refsynopsisdiv>
<synopsis>
TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable>
TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...]
</synopsis>
</refsynopsisdiv>
@ -28,10 +28,10 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable>
<title>Description</title>
<para>
<command>TRUNCATE</command> quickly removes all rows from a
table. It has the same effect as an unqualified
<command>DELETE</command> but since it does not actually scan the
table it is faster. This is most useful on large tables.
<command>TRUNCATE</command> quickly removes all rows from a set of
tables. It has the same effect as an unqualified
<command>DELETE</command> on each table, but since it does not actually
scan the tables it is faster. This is most useful on large tables.
</para>
</refsect1>
@ -43,7 +43,7 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable>
<term><replaceable class="PARAMETER">name</replaceable></term>
<listitem>
<para>
The name (optionally schema-qualified) of the table to be truncated.
The name (optionally schema-qualified) of a table to be truncated.
</para>
</listitem>
</varlistentry>
@ -54,14 +54,15 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable>
<title>Notes</title>
<para>
<command>TRUNCATE</> cannot be used if there are foreign-key references
to the table from other tables. Checking validity in such cases would
require table scans, and the whole point is not to do one.
<command>TRUNCATE</> cannot be used on a table that has foreign-key
references from other tables, unless all such tables are also truncated
in the same command. Checking validity in such cases would require table
scans, and the whole point is not to do one.
</para>
<para>
<command>TRUNCATE</> will not run any user-defined <literal>ON
DELETE</literal> triggers that might exist for the table.
DELETE</literal> triggers that might exist for the tables.
</para>
</refsect1>
@ -69,10 +70,10 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable>
<title>Examples</title>
<para>
Truncate the table <literal>bigtable</literal>:
Truncate the tables <literal>bigtable</literal> and <literal>fattable</literal>:
<programlisting>
TRUNCATE TABLE bigtable;
TRUNCATE TABLE bigtable, fattable;
</programlisting>
</para>
</refsect1>