2008/11/15 Tom Lane <tgl@xxxxxxxxxxxxx>
OK, thanks for cleaning-up some mystery.
But, returning to original Q: Do anyone known why does it choose plan from OR-plan.txt instead of union-plan.txt? The first is cost=4588.13..960900482668.95, the latter is cost=266348.42..272953.14 according to statistics postgres have, so I suppose planner would select it if it could evaluate it.
"=?ISO-8859-5?B?svbi0Nv22SDC2Nzn2OjY3Q==?=" <tivv00@xxxxxxxxx> writes:
> I am not. I can't see how materialize can multiply number of rows it getsIs it the right-hand input of a merge join? If so you're looking at
> from sort by 100.
mark/restore rescans, ie, repeated fetches of the same tuples. There
must be a huge number of duplicate join keys in that relation to make
for such an increase though. Normally the planner avoids putting a
table with lots of duplicates as the RHS of a merge, but if it doesn't
have good statistics for the join key then it might not realize the
problem.
OK, thanks for cleaning-up some mystery.
But, returning to original Q: Do anyone known why does it choose plan from OR-plan.txt instead of union-plan.txt? The first is cost=4588.13..960900482668.95, the latter is cost=266348.42..272953.14 according to statistics postgres have, so I suppose planner would select it if it could evaluate it.
