Re: inheritance: planning time vs children number vs column number

Marc Cousin <cousinmarc(at)gmail(dot)com> writes:
> The Monday 28 February 2011 13:57:45, Heikki Linnakangas wrote :
>> Testing here with a table with 1000 columns and 100 partitions, about
>> 80% of the planning time is looking up the statistics on attribute
>> width, to calculate average tuple width. I don't see O(n^2) behavior,
>> though, it seems linear.

> It is only based on experimentation, for my part, of course

> If you measure the planning time, modifying either the columns or the
> partitions number, the square root of the planning time is almost perfectly
> proportional with the parameter you're playing with.

Could we see a concrete example demonstrating that? I agree with Heikki
that it's not obvious what you are testing that would have such behavior.
I can think of places that would have O(N^2) behavior in the length of
the targetlist, but it seems unlikely that they'd come to dominate
runtime at a mere 1000 columns.

regards, tom lane