On 2013-05-16 17:52, David Kerr wrote:
On Fri, May 10, 2013 at 11:01:15AM -0500, Larry Rosenman wrote:
- On 2013-05-10 10:57, Tom Lane wrote:
- >Larry Rosenman <ler@xxxxxxxxxx> writes:
- >On 2013-05-10 09:14, Tom Lane wrote:
- >... and verify you get a cheap plan for each referencing table.
- >
- >We don't :(
- >
- >Ugh. I bet the problem is that in some of these tables, there are
lots
- >and lots of duplicate account ids, such that seqscans look like a
good
- >bet when searching for an otherwise-unknown id. You don't see this
- >with a handwritten test for a specific id because then the planner
can
- >see it's not any of the common values.
- >
- >9.2 would fix this for you --- any chance of updating?
- >
- > regards, tom lane
- I'll see what we can do. I was looking for a reason, this may be it.
-
- Thanks for all your help.
I haven't seen an explain for this badboy, maybe I missed it (even just
a
plain explain might be useful) but you may be running into a situation
where
the planner is trying to materialize or hash 2 big tables.
I've actually run into that in the past and had some success in PG9.1
running
with enable_material=false for some queries.
It might be worth a shot to play with that and
enable_hashagg/enable_hashjoin=false
(If you get a speedup, it points to some tuning/refactoring that could
happen)
Dave
I'll take a look tomorrow, but we WERE seeing Seq Scan's against
multi-million
row tables, so I suspect Tom is right on with the replanning that's in
9.2 fixing
it, and I'm in the process of validating that.
I'll have that news tomorrow as well. (updated a test box with the
production
DB to 9.2.4 and am running a Vacuum Analyze and then will redo this test
with that
DB/Engine.
--
Larry Rosenman http://www.lerctr.org/~ler
Phone: +1 214-642-9640 (c) E-Mail: ler@xxxxxxxxxx
US Mail: 430 Valona Loop, Round Rock, TX 78681-3893
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