Re: Constraint exclusion on UNION ALL subqueries with WHERE conditions

=?ISO-8859-1?Q?Gunnlaugur_=DE=F3r_Briem?= <gunnlaugur(at)gmail(dot)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 of the 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