Horton

Re: Showing primitive index scan count in EXPLAIN ANALYZE (for skip scan and SAOP scans)

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-08-28T13:41:16Z
Lists: pgsql-hackers 
On Wed, Aug 28, 2024 at 9:35 AM Robert Haas <robertmhaas@gmail.com> wrote:
> > If you think it's important to have this info on all indexes then I'd
> > prefer the pgstat approach over adding a field in IndexScanDescData.
> > If instead you think that this is primarily important to expose for
> > nbtree index scans, then I'd prefer putting it in the BTSO using e.g.
> > the index AM analyze hook approach, as I think that's much more
> > elegant than this.
>
> I agree with this analysis. I don't see why IndexScanDesc would ever
> be the right place for this.

Then what do you think is the right place?

There's no simple way to get to the planstate instrumentation from
within an index scan. You could do it by passing it down as an
argument to either ambeginscan or amrescan. But, realistically, it'd
probably be better to just add a pointer to the instrumentation to the
IndexScanDesc passed to amrescan. That's very close to what I've done
already.

-- 
Peter Geoghegan

Commits

  1. Show index search count in EXPLAIN ANALYZE, take 2.

  2. Show index search count in EXPLAIN ANALYZE.

  3. Allow usage of match_orclause_to_indexcol() for joins

  4. Fix nbtree pgstats accounting with parallel scans.

  5. Enhance nbtree ScalarArrayOp execution.

  6. Fix EXPLAIN ANALYZE of hash join when the leader doesn't participate.