Does PostgreSQL use the COMMUTATOR property of an operator to determine if flip-flopped arguments can be collapsed.
I used to think it did until someone pointed it doesn't - For example in the below
SELECT b.*
FROM boszip b INNER JOIN landparcels l
ON (b.the_geom && l.the_geom AND l.the_geom && b.the_geom AND l.the_geom && b.the_geom )
WHERE l.gid = b.gid and b.gid = l.gid
limit 1
If I look at the query plan - I see the plan has reduced things down to
l.gid = b.gid AND (b.the_geom && l.the_geom AND l.the_geom && b.the_geom)
Why is (b.the_geom && l.the_geom AND l.the_geom && b.the_geom) not reduced down to just
b.the_geom && l.the_geom
even though && is defined as the commutator of &&?
Thanks,
Regina
The substance of this message, including any attachments, may be confidential, legally privileged and/or exempt from disclosure pursuant to Massachusetts law. It is intended solely for the addressee. If you received this in error, please contact the sender and delete the material from any computer.
Help make the earth a greener place. If at all possible resist printing this email and join us in saving paper.
