Laurenz, thank You very much for Your comments! On Sun, Mar 25, 2018 at 07:12:08AM +0200, Laurenz Albe wrote: ! Your reported execution times don't match the time reported in the ! EXPLAIN output... Should these match? It seems the EXPLAIN (ANALYZE, BUFFERS) does additional things, not just execute the query. ! 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. I've seen this, but do not fully understand it yet. ! Setting "enable_nestloop = off" is as coarse as forcing "from_collapse = 1" ! and will negatively impact other queries - if it helps at all. Since this query is already put into a function, I found I can easily set from_collapse=1 only for this function, by means of "ALTER FUNCTION ... SET ...", so it does only influence this query. It seems this is the most straight-forward solution here. rgds, P.
