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
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
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