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
From e032752680193a26e21c3927968f72bed20db99e Mon Sep 17 00:00:00 2001 From: test <test> Date: Sun, 3 May 2026 16:05:54 +0200 Subject: [PATCH] Improve docs for EXPLAIN (IO) Commit 681daed931 introduced a new EXPLAIN options "IO", but the docs did not explain what information is added to the output. Expand the description a little bit, similarly to the other EXPLAIN options. While at it, fix a typo in the first sentence. Reported-by: FIXME link to the typo report Author: Tomas Vondra <[email protected]> --- doc/src/sgml/ref/explain.sgml | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/doc/src/sgml/ref/explain.sgml b/doc/src/sgml/ref/explain.sgml index e95e19081e1..d0644bca038 100644 --- a/doc/src/sgml/ref/explain.sgml +++ b/doc/src/sgml/ref/explain.sgml @@ -303,7 +303,13 @@ ROLLBACK; <term><literal>IO</literal></term> <listitem> <para> - Include information on I/O performed by scan nodes proving such information. + Include information on I/O performed by scan nodes providing such + information. + Specifically, include information about the prefetch queue (the average + and maximum distance, and the capacity), and information about issued + I/O requests (number of requests and an average request size, number of + I/O waits, and an average number of concurrent I/O requests). + In text format, only non-zero values are printed. This parameter may only be used when <literal>ANALYZE</literal> is also enabled. It defaults to <literal>FALSE</literal>. </para> -- 2.54.0
