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From: Andres Freund <andres@anarazel.de>
To: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: Masahiro Ikeda <ikedamsh@oss.nttdata.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Add statistics to pg_stat_wal view for wal related parameter tuning
Date: Mon, 21 Dec 2020 16:39:35 -0800
Message-ID: <20201222003935.47aoxfmokltlrlf2@alap3.anarazel.de> (raw)
In-Reply-To: <20201221211650.k7b53tcnadrciqjo@alap3.anarazel.de>
References: <e3135545ffe792d6d636ebc40ebf022d@oss.nttdata.com>
	<e28c5f5e-363e-70c1-a200-28a8798ed8e2@oss.nttdata.com>
	<11e81f0b7d90dd69077d3d964a9a4da9@oss.nttdata.com>
	<79620b5c-ecf1-3d4f-80b5-7e311b7a0662@oss.nttdata.com>
	<89de5056627ebdd144967959bd789bd6@oss.nttdata.com>
	<58ccc451-8429-ce44-f0b7-773c8dfedf45@oss.nttdata.com>
	<7eb4ebd487b53200bde98ba2f0a7e789@oss.nttdata.com>
	<f9197102-4cb4-dfb6-02a4-b8e237c7699f@oss.nttdata.com>
	<451365b7-9e22-211e-428f-fc90ebc715bc@oss.nttdata.com>
	<20201221211650.k7b53tcnadrciqjo@alap3.anarazel.de>

Hi,

On 2020-12-21 13:16:50 -0800, Andres Freund wrote:
> On 2020-12-02 13:52:43 +0900, Fujii Masao wrote:
> > Pushed. Thanks!
>
> Why are wal_records/fpi long, instead of uint64?
> 	long		wal_records;	/* # of WAL records produced */
> 	long		wal_fpi;		/* # of WAL full page images produced */
> 	uint64		wal_bytes;		/* size of WAL records produced */
>
> long is only 4 byte e.g. on windows, and it is entirely possible to wrap
> a 4 byte record counter. It's also somewhat weird that wal_bytes is
> unsigned, but the others are signed?
>
> This is made doubly weird because on the SQL level you chose to make
> wal_records, wal_fpi bigint. And wal_bytes numeric?

Some more things:
- There's both PgStat_MsgWal WalStats; and static PgStat_WalStats walStats;
  that seems *WAY* too confusing. And the former imo shouldn't be
  global.
- AdvanceXLInsertBuffer() does WalStats.m_wal_buffers_full, but as far
  as I can tell there's nothing actually sending that?

- Andres





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  Subject: Re: Add statistics to pg_stat_wal view for wal related parameter tuning
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