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: Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-08-29T17:33:32Z
Lists: pgsql-hackers 
On Wed, Aug 28, 2024 at 9:25 AM Robert Haas <robertmhaas@gmail.com> wrote:
> On Tue, Aug 27, 2024 at 3:04 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I kind of had that reaction too initially, but I think that was mostly
> because "Primitive Index Scans" seemed extremely unclear. I think
> "Index Searches" is pretty comprehensible, honestly. Why shouldn't
> someone be able to figure out what that means?

Worth noting that Lukas Fittl made a point of prominently highlighting
the issue with how this works when he explained the Postgres 17 nbtree
work:

https://pganalyze.com/blog/5mins-postgres-17-faster-btree-index-scans

And no, I wasn't asked to give any input to the blog post. Lukas has a
general interest in making the system easier to understand for
ordinary users. Presumably that's why he zeroed in on this one aspect
of the work. It's far from an esoteric implementation detail.

-- 
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.