Subject: Missing information on Expressional Indexes

From: David Fetter <[email-masked]>
Date: Tue, 16 Mar 2010 17:14:01 -0700

Folks,

I think this page should mention that the expressions used in an
expressional index need to be equivalent to an IMMUTABLE function, and
the docs don't say so.  The change should also be back-patched.
<http://www.postgresql.org/docs/current/static/indexes-expressional.html>

I'm thinking that something along the lines of, "Expressions are
limited to those which are equivalent to an [link]IMMUTABLE[/link]
function."

Anybody have a better suggestion for wording?

Cheers,
David.
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From: Tom Lane <[email-masked]>
Date: Wed, 17 Mar 2010 00:47:51 -0400

David Fetter <[email-masked]> writes:
> the docs don't say so.

Sure they do, see CREATE INDEX:

	All functions and operators used in an index definition must be
	"immutable" ...

			regards, tom lane