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From: Shardul Borhade <shardul@dbtune.com>
Date: Fri, 31 Oct 2025 09:17:22 +0100
Message-ID: 
 <CA+xwDujmUnm_vbojvvRz87tuwTA90CZrC8HGor99Nv9RtJERRg@mail.gmail.com>
Subject: Question on pg_stat_io showing zero reads/writes for I/O workers
To: pgsql-admin@lists.postgresql.org
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Hi team,

I=E2=80=99m running into an issue with pg_stat_io. When I run the following=
 query:

SELECT backend_type, reads, writes, read_time
FROM pg_stat_io
WHERE backend_type LIKE '%io%';

I consistently get:

 backend_type | reads | writes | read_time
--------------+-------+--------+-----------
 io worker    |     0 |      0 |         0
 io worker    |     0 |      0 |         0
 io worker    |     0 |      0 |         0
 io worker    |     0 |      0 |         0
 io worker    |     0 |      0 |         0
 io worker    |     0 |      0 |         0
 io worker    |       |      0 |
 io worker    |     0 |      0 |         0
(8 rows)

I tried running a heavy sequential scan on a 55 GB table as well as a
bitmap heap scan, but the reads and writes columns still show zero.

However, I can clearly observe performance differences when I tune the
io_workers configuration, so I believe they are active.

Am I missing something here? Could someone please help me understand why
the stats aren=E2=80=99t being reflected in pg_stat_io? Do I need to enable=
 any
other server parameter to log this information?

Thanks and regards,

Shardul B

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<div dir=3D"ltr"><p>Hi team,</p>
<p>I=E2=80=99m running into an issue with <code>pg_stat_io</code>. When I r=
un the following query:</p>
<pre><code class=3D"gmail-language-sql">SELECT backend_type, reads, writes,=
 read_time
FROM pg_stat_io
WHERE backend_type LIKE &#39;%io%&#39;;
</code></pre>
<p>I consistently get:</p>
<pre><code> backend_type | reads | writes | read_time=20
--------------+-------+--------+-----------
 io worker    |     0 |      0 |         0
 io worker    |     0 |      0 |         0
 io worker    |     0 |      0 |         0
 io worker    |     0 |      0 |         0
 io worker    |     0 |      0 |         0
 io worker    |     0 |      0 |         0
 io worker    |       |      0 |         =20
 io worker    |     0 |      0 |         0
(8 rows)
</code></pre>
<p>I tried running a heavy sequential scan on a 55 GB table as well as a bi=
tmap heap scan, but the <code>reads</code> and <code>writes</code> columns =
still show zero.</p>
<p>However, I can clearly observe performance differences when I tune the <=
code>io_workers</code> configuration, so I believe they are active.</p>
<p>Am I missing something here? Could someone please help me understand why=
 the stats aren=E2=80=99t being reflected in <code>pg_stat_io</code>? Do I =
need to enable any other server parameter to log this information?</p>
<p>Thanks and regards,<br></p><p>Shardul B</p></div>

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