Re: EXPLAIN: showing ReadStream / prefetch stats

From: Tomas Vondra <tomas(at)vondra(dot)me>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Melanie Plageman <melanieplageman(at)gmail(dot)com>, Lukas Fittl <lukas(at)fittl(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: EXPLAIN: showing ReadStream / prefetch stats
Date: 2026-05-04 13:51:20
Message-ID: afa26355-0170-4dfc-a381-024c052d26bf@vondra.me
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Hi,

While looking for something in the EXPLAIN docs, I realized the docs
added by 681daed93169 are considerably less detailed that for the other
EXPLAIN options. It only said "information on I/O" provided by the scan
node, while the other options go into much more details.

The attached patch improves that a little bit - it lists the counters
added to explain. I'll consider going into a little bit more detail,
e.g. regarding what "capacity" or "waits" means.

I'll add this as an open item for PG19, so that I don't forget about it.

regards

--
Tomas Vondra

Attachment Content-Type Size
0001-Improve-docs-for-EXPLAIN-IO.patch text/x-patch 1.6 KB

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