Message-ID: <5315aedc-fbca-1556-c5de-dc2e00b23a14@oss.nttdata.com>
Date: Tue, 25 Apr 2023 22:51:14 +0900
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To: pgsql-hackers@postgresql.org
From: Fujii Masao <masao.fujii@oss.nttdata.com>
Subject: pg_stat_io for the startup process
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Hi,

Regarding pg_stat_io for the startup process, I noticed that the counters
are only incremented after the startup process exits, not during WAL replay
in standby mode. This is because pgstat_flush_io() is only called when
the startup process exits. Shouldn't it be called during WAL replay as well
to report IO statistics by the startup process even in standby mode?

Also, the pg_stat_io view includes a row with backend_type=startup and
context=vacuum, but it seems that the startup process doesn't perform
any I/O operations with BAS_VACUUM. If this understanding is right,
shouldn't we omit this row from the view? Additionally, I noticed that
the view also includes a row with backend_type=startup and
context=bulkread / bulkwrite. Do these operations actually occur
during startup process?

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION