Re: PostgreSQL OR performance

"=?ISO-8859-5?B?svbi0Nv22SDC2Nzn2OjY3Q==?=" <tivv00@gmail.com> writes:
> I am not. I can't see how materialize can multiply number of rows it gets
> from sort by 100.

Is it the right-hand input of a merge join?  If so you're looking at
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.

            regards, tom lane