From: Masahiro Ikeda <ikedamsh@oss.nttdata.com>
To: lchch1990@sina.cn
Cc: Amit Kapila <amit.kapila16@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Add statistics to pg_stat_wal view for wal related parameter tuning
Date: Thu, 22 Oct 2020 10:34:28 +0900
Message-ID: <ac8b1f5e589932254efe373e252e5dcb@oss.nttdata.com> (raw)
In-Reply-To: <2020102114544806663477@sina.cn>
References: <35ef960128b90bfae3b3fdf60a3a860f@oss.nttdata.com>
<CAA4eK1JbbP-QmZWiXwK+H-ZauJCGR6vbAVoGdyx_TTxRPuXzhQ@mail.gmail.com>
<06bc2d405b086a72fb14657de9befae8@oss.nttdata.com>
<2020102114544806663477@sina.cn>
On 2020-10-21 15:54, lchch1990@sina.cn wrote:
> I think it's really a more convenient way to collect wal usage
> information,
> with it we can query when I want. Several points on my side:
Thanks for your comments.
> 1. It will be nice If you provide a chance to reset the information in
> WalStats,
> so that we can reset it without restart the database.
I agree.
Now, pg_stat_wal supports reset all informantion in WalStats
using pg_stat_reset_shared('wal') function.
Isn't it enough?
> 2. I think 'wal_write_backend' is mean wal write times happen in
> backends. The describe in document is not so clear, suggest rewrite
> it.
OK, I'll rewrite to "Total number of times backends write WAL data to
the disk".
> 3. I do not think it's a correct describe in document for
> 'wal_buffers_full'.
Where should I rewrite the description? If my understanding is not
correct, please let me know.
> 4. Quite strange to collect twice in XLogInsertRecord() for
> xl_tot_len,
> m_wal_records, m_wal_fpi.
Yes, Amit-san pointed me that too.
I'll remove them from pg_stat_wal since pg_stat_statements and vacuum
log
already shows the related statistics and there is a comment it's enough.
Anyway, if you need to the accumulated above statistics in pg_stat_wal,
please let me know.
> 5. I notice some code in issue_xlog_fsync() function to collect sync
> info,
> a standby may call the issue_xlog_fsync() too, which do not want to
> to collect this info. I think this need some change avoid run by
> standby
> side.
Thanks, I will fix it.
Regards,
--
Masahiro Ikeda
NTT DATA CORPORATION
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To: pgsql-hackers@postgresql.org
Cc: ikedamsh@oss.nttdata.com, lchch1990@sina.cn, amit.kapila16@gmail.com
Subject: Re: Add statistics to pg_stat_wal view for wal related parameter tuning
In-Reply-To: <ac8b1f5e589932254efe373e252e5dcb@oss.nttdata.com>
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