Re: Query too slow

Stephan Szabo <sszabo@megazone.bigpanda.com> writes:
> On Tue, 26 Aug 2003, Ang Chin Han wrote:
>> Veering aside a bit, since we usually pinpoint performance problems by
>> looking at EXPLAIN ANALYZE's differences between the planner's
>> estimation and actual execution's stats, what's involved in parsing the
>> EXPLAIN ANALYZE results, and highlighting the places where they are way
>> different? Bold, underline, or put some asterisks in front of those steps.

> The hardest part is determining where it matters I think.  You can use the
> row counts as the base for that, but going from 1 row to 50 is not
> necessarily going to be an issue, but it might be if a nested loop is
> chosen.

We've been chatting about this idea among the Red Hat group.  The RHDB
Visual Explain tool (get it at http://sources.redhat.com/rhdb/) already
computes the percent of total runtime represented by each plan node.
It seems like we could highlight nodes based on a large difference
between estimated and actual percentage, or just highlight the nodes
that are more than X percent of the runtime.

            regards, tom lane