Re: referring to computed values from the select list in the where and order clauses - Mailing list pgsql-general

On Monday 01 March 2004 01:04, Stephen Howard wrote:
> I've got a moderately complex function defined which i then want to be
>
> able to test the value of, as well as select the value:
>
> select id, vector_cosine(document,'[ qw( foo,bar,baz )]') as threshold
> from search_vectorspace where threshold > 0 order by threshold desc;

Can't be done that way, I'm afraid. The aliasing is defined as occuring after
the where clause has been evaluated.

However, you can mark functions as immutable/stable/volatile which can allow
PG to cache the query results. See the manuals (CREATE FUNCTION) for details.

--
  Richard Huxton
  Archonet Ltd