Re: Query too slow

Bruce Momjian wrote:
> 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

No one commented, so I had to guess --- I added it.

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