Re: Constraint exclusion on UNION ALL subqueries with WHERE conditions - Mailing list pgsql-performance

=?ISO-8859-1?Q?Gunnlaugur_=DE=F3r_Briem?= <gunnlaugur@gmail.com> writes:
> I did this:

> CREATE VIEW unionview AS
>   SELECT col, otherstuff FROM (heavy subquery)
>   WHERE col BETWEEN 1 AND 3
>   UNION ALL
>   SELECT col, otherstuff FROM (another heavy subquery)
>   WHERE col BETWEEN 4 AND 6;

> hoping that the planner could use the WHERE conditions (like it would use check constraints on tables) to exclude one
ofthe subqueries, for a query like: 

> SELECT * FROM unionview WHERE col=2;

> But it doesn't. (In PostgreSQL 8.4.5, at least.)

Works for me in 8.4.8.  Do you have constraint_exclusion set to ON?

            regards, tom lane