Peter wrote: > On Fri, Mar 23, 2018 at 10:14:19AM -0400, Tom Lane wrote: > > ! It's conceivable that the OP's problem is actually planning time > ! (if the query joins sufficiently many tables) and that restricting > ! the cost of the join plan search is really what he needs to do. > > Negative. Plnning time 10 to 27 ms. Execution time 600 to 6300 ms. > > ! Lacking any further information about the problem, we can't say. > ! We can, however, point to > ! https://wiki.postgresql.org/wiki/Slow_Query_Questions > ! concerning how to ask this type of question effectively. > > I strongly hope the data that I sent as followup will now > suffice Your expectations. Your reported execution times don't match the time reported in the EXPLAIN output... The cause of the long execution time is clear: The row count of the join between "places" (WHERE platz = 'WAEHR'), "wpnames" and "places AS places_1" is underestimated by a factor of 10 (1 row instead of 10). The nested loop join that is chosen as a consequence is now executed 10 times instead of the estimated 1 time, which is where almost all the execution time is spent. The question how to fix that is more complicated, and I cannot solve it off-hand with a complicated query like that. Setting "enable_nestloop = off" is as coarse as forcing "from_collapse = 1" and will negatively impact other queries - if it helps at all. You'll probably have to rewrite the query. Sorry that I cannot be of more help. Yours, Laurenz Albe -- Cybertec | https://www.cybertec-postgresql.com
