Re: Inconsistant query plan

Daniel Gish wrote:
> Hi,
> Thanks for your response.  The actual query is below; the joins are only 4
> deep.  Adjusting the stats target did help, but not dramatically.
>
>               QUERY PLAN
> ----------------------------------------------------------------------------
> ----------------------------------------------------------------------------
> ---------------------------------------
>  Nested Loop  (cost=978.19..37161.81 rows=133 width=4) (actual
> time=2511.676..2511.676 rows=0 loops=1)
>    ->  Merge Join  (cost=978.19..22854.00 rows=4244 width=4) (actual
> time=1718.420..2510.128 rows=92 loops=1)
 > ...
 >               ->  Nested Loop  (cost=0.00..974.33 rows=113 width=8) (actual
time=0.078..2.305 rows=19 loops=1)

I have a similar problem recently. An importat diagnostic tool for these issues
is the pg_stats view. Let me suggest that you post the relevant lines from
pg_stats, so that with some help you will be able to discover what data advises
the query planner to overestimate the cardinality of some joins and
underestimate others.


Alex


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