Re: Parallel Bitmap Heap Scan reports per-worker stats in EXPLAIN ANALYZE

David Rowley <dgrowleyml@gmail.com>

From: David Rowley <dgrowleyml@gmail.com>

To: Tomas Vondra <tomas.vondra@enterprisedb.com>

Cc: Dilip Kumar <dilipbalaut@gmail.com>, David Geier <geidav.pg@gmail.com>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>

Date: 2024-07-09T02:44:23Z

Lists: pgsql-hackers

Commits

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Show Parallel Bitmap Heap Scan worker stats in EXPLAIN ANALYZE
- 5a1e6df3b84c 18.0 landed
Widen lossy and exact page counters for Bitmap Heap Scan
- 7340d9362a79 18.0 landed
Remove redundant snapshot copying from parallel leader to workers
- 84c18acaf690 17.0 cited

On Tue, 9 Jul 2024 at 11:51, David Rowley <dgrowleyml@gmail.com> wrote:
> I think we should consider aligning Parallel Hash
> with the other Parallel node behaviour.

I looked at that and quickly realised that it makes sense that
Parallel Hash does something different here.  All the workers are
contributing to building the same hash table, so they're all going to
show the same set of values, provided they managed to help building
it.

We're able to tell how much each worker helped according to EXPLAIN
(ANALYZE, VERBOSE)'s Worker N: rows=n output.  I don't think there's
anything else not already shown that would be interesting to know per
worker.

David