CREATE VIEW course AS
SELECT
e.code AS educode,
e.name AS eduname,
t.code AS topiccode,
t.name AS topicname,
c.id,
c.topic,
c.code,
c.hrs,
c.num,
c.name,
c.descr,
c.created,
c.modified,
c.editor,
c.status
FROM
_edu e,
_topic t,
_course c
WHERE
c.topic = t.id -- maybe this should be swapped
AND
t.edu = e.id -- with this ??
;
psql=> explain select * from course;
NOTICE: QUERY PLAN:
Merge Join (cost=4.14..4.42 rows=8 width=238)
-> Sort (cost=2.63..2.63 rows=5 width=60)
-> Merge Join (cost=2.38..2.57 rows=5 width=60)
-> Sort (cost=1.30..1.30 rows=11 width=32)
-> Seq Scan on _topic (cost=0.00..1.11 rows=11 width=32)
-> Sort (cost=1.08..1.08 rows=4 width=28)
-> Seq Scan on _edu (cost=0.00..1.04 rows=4 width=28)
-> Sort (cost=1.52..1.52 rows=17 width=178)
-> Seq Scan on _course (cost=0.00..1.17 rows=17 width=178)
EXPLAIN
there's FOUR sort items mentioned there, and that's before the
merge join (results will not be sorted in any particular order).
which document will allay my 'holy cow is this ever gonna slow
down my database performance' concerns? (perhaps by saying that
sorting is just a myth, or by telling me how to get this puppy to
not sort at all -- and to use the indexes that i've defined for
all these joined fields...!)
--
It is always hazardous to ask "Why?" in science, but it is often
interesting to do so just the same.
-- Isaac Asimov, 'The Genetic Code'
will@serensoft.com
http://newbieDoc.sourceforge.net/ -- we need your brain!
http://www.dontUthink.com/ -- your brain needs us!
