Re: Query too slow

Tom Lane wrote:
> Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)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.

Is there a TODO here? Perhaps:

o Have EXPLAIN ANALYZE highlight poor optimizer estimates

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