Re: Order by (for 15 rows) adds 30 seconds to query time - Mailing list pgsql-performance

From Kevin Grittner
Subject Re: Order by (for 15 rows) adds 30 seconds to query time
Date
Msg-id 4B361A6E020000250002D965@gw.wicourts.gov
Whole thread Raw
Responses Re: Order by (for 15 rows) adds 30 seconds to query time
List pgsql-performance
Tom Lane wrote:

> That does look weird. Do we have a self-contained test case?

I've been tinkering with this and I now have a self-contained test
case (SQL statements and run results attached). I've debugged through
it and things don't seem right in set_append_rel_pathlist, since
childrel->rows seems to contain the total rows in each table rather
than the number which meet the join conditions. That is reflected in
the output from OPTIMIZER_DEBUG logging, but not in the query plan
from ANALYZE?

I'm afraid I'm a bit stuck on getting farther.  Hopefully this much
will be of use to someone.  If you could point out where I should
have looked next, I'd be grateful.  :-)

-Kevin


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