Folks,
Please find enclosed a patch that shows how to get a quick
approximation of count(*) on a table.
Cheers,
D
--
David Fetter [EMAIL PROTECTED] http://fetter.org/
phone: +1 510 893 6100 mobile: +1 415 235 3778
Remember to vote!
Index: doc/src/sgml/func.sgml
===================================================================
RCS file: /projects/cvsroot/pgsql/doc/src/sgml/func.sgml,v
retrieving revision 1.241
diff -c -r1.241 func.sgml
*** doc/src/sgml/func.sgml 14 Mar 2005 18:31:19 -0000 1.241
--- doc/src/sgml/func.sgml 24 Mar 2005 16:25:55 -0000
***************
*** 7330,7339 ****
</para>
<para>
! Unfortunately, there is no similarly trivial query that can be
! used to improve the performance of <function>count()</function>
! when applied to the entire table.
</para>
</note>
</sect1>
--- 7330,7348 ----
</para>
<para>
! When the table has been <command>VACUUM</command>ed recently, but
! only then, a good approximation of count(*) for an entire table
! can be obtained as follows:
! <programlisting>
! SELECT reltuples FROM pg_class WHERE relname = 'sometable';
! </programlisting>
! </para>
!
! <para>
! Unfortunately, there is not yet a general trivial query that can
! be used to improve the performance of <function>count()</function>.
</para>
+
</note>
</sect1>
---------------------------(end of broadcast)---------------------------
TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
