Re: Many fields in one table or many tables?

Josh Berkus <josh@agliodbs.com> writes:
> Suggestion 3: There was an issue in 7.3 with table rows which are overly broad
> -- some problems with PSQL, I believe.

Not sure about PSQL, but I think there still are some performance issues
in the backend with SELECTs involving more than a couple hundred
targetlist entries.  These are probably fixable at not-very-large effort
but we haven't made any consistent push to find and fix the trouble
spots.  The issues that I recall are O(N^2) problems (doubly nested
loops) so the performance with ~100 entries is no problem but it gets
rapidly worse above that.  You could hit this even with ~100-column
tables if you try to select all columns from a join of two or more.

            regards, tom lane