Jim C. Nasby wrote:
> This was recently discussed on -docs and I believe a patch was applied
> to at least HEAD.
Yep, patch attached. Any improvements?
---------------------------------------------------------------------------
>
> On Mon, Jan 30, 2006 at 10:33:35AM +0000, dueyduey@freemail.hu wrote:
> >
> > The following bug has been logged online:
> >
> > Bug reference: 2223
> > Logged by:
> > Email address: dueyduey@freemail.hu
> > PostgreSQL version: 8.1
> > Operating system: linux
> > Description: Misleading info in docs on volatility level of functions
> > Details:
> >
> > Hi, all!
> > The documentation on how to and why declare a function STABLE or IMMUTABLE
> > is very laconic. It makes clear what promises I make when determining the
> > volatility of my functions but it fails to point out what exactly I can
> > expect in turn for my promises.
> > See also the discussion on bug#2150 on the pgsql-bugs list.
> > Thanks for bothering.
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 9: In versions below 8.0, the planner will ignore your desire to
> > choose an index scan if your joining column's datatypes do not
> > match
> >
>
> --
> Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
> Pervasive Software http://pervasive.com work: 512-231-6117
> vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
>
> ---------------------------(end of broadcast)---------------------------
> TIP 6: explain analyze is your friend
>
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
Index: xfunc.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/xfunc.sgml,v
retrieving revision 1.109
retrieving revision 1.110
diff -c -c -r1.109 -r1.110
*** xfunc.sgml 29 Nov 2005 01:46:54 -0000 1.109
--- xfunc.sgml 19 Jan 2006 22:52:08 -0000 1.110
***************
*** 1,5 ****
<!--
! $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.109 2005/11/29 01:46:54 alvherre Exp $
-->
<sect1 id="xfunc">
--- 1,5 ----
<!--
! $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.110 2006/01/19 22:52:08 momjian Exp $
-->
<sect1 id="xfunc">
***************
*** 899,911 ****
<para>
A <literal>STABLE</> function cannot modify the database and is
guaranteed to return the same results given the same arguments
! for all calls within a single surrounding query. This category
! allows the optimizer to optimize away multiple calls of the function
! within a single query. In particular, it is safe to use an expression
! containing such a function in an index scan condition. (Since an
! index scan will evaluate the comparison value only once, not once at
! each row, it is not valid to use a <literal>VOLATILE</> function in
! an index scan condition.)
</para>
</listitem>
<listitem>
--- 899,911 ----
<para>
A <literal>STABLE</> function cannot modify the database and is
guaranteed to return the same results given the same arguments
! for all rows within a single statement. This category allows the
! optimizer to optimize multiple calls of the function to a single
! call. In particular, it is safe to use an expression containing
! such a function in an index scan condition. (Since an index scan
! will evaluate the comparison value only once, not once at each
! row, it is not valid to use a <literal>VOLATILE</> function in an
! index scan condition.)
</para>
</listitem>
<listitem>
