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

From: Peter Geoghegan <pg(at)bowt(dot)ie>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Showing primitive index scan count in EXPLAIN ANALYZE (for skip scan and SAOP scans)
Date: 2025-03-06 18:58:04
Message-ID: CAH2-Wz=d0qHvugL0Mc8+diDPhXZw86Twr532-cr61YUu8wq46w@mail.gmail.com
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On Thu, Mar 6, 2025 at 1:54 PM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> Hmm, it seems weird that you can't get a hold of that structure to me.
> Why can't you just go find it in the DSM?

Sorry, I was unclear.

One reason is that there isn't necessarily anything to find.
Certainly, when I try this out with a debugger, even the B-Tree scan
doesn't have doesn't even have IndexScanDescData.parallel_scan set. It
isn't actually a parallel B-Tree scan. It is a
serial/non-parallel-aware index scan that is run from a parallel
worker, and feeds its output into a gather merge node despite all
this.

--
Peter Geoghegan

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