On Nov 14, 2005, at 3:52 PM, Steve Wampler wrote:
Scott Lamb wrote:
On Nov 14, 2005, at 2:07 PM, Steve Wampler wrote:
# SELECT at.id FROM "tmp_table2" at, "tmp_tabl2e" a
# WHERE at.id=a.id and a.name='obsid' and a.value='oid080505';
Isn't this equivalent?
select id from tmp_table2 where name = 'obsid' and value =
'oid080505';
Probably, the user based the above on a query designed to find
all rows with the same id as those rows that have a.name='obsid' and
a.value='oid080505'.
Well, this indirection is only significant if those two sets can
differ. If (A) you meant "tmp_table2" when you wrote "tmp_tabl2e", so
this is a self-join, and (B) there is a primary key on "id", I don't
think that can ever happen.
It appears (to me) to be the Seq Scan on tmp_table2
that is the killer here. If we put an index on, would it help?
On...tmp_table2.id? If it is a primary key, there already is one. If
not, yeah, I expect it would help.
--
Scott Lamb <http://www.slamb.org/>
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