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help / color / mirror / Atom feedFrom: Andres Freund <andres@anarazel.de>
To: Fujii Masao <masao.fujii@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Martijn van Oosterhout <kleptog@svana.org>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: WAL logging problem in 9.4.3?
Date: Fri, 10 Jul 2015 12:29:02 +0200
Message-ID: <20150710102902.GL340@alap3.anarazel.de> (raw)
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On 2015-07-10 19:23:28 +0900, Fujii Masao wrote:
> Maybe I'm missing something. But I start wondering why TRUNCATE
> and INSERT (or even all the operations on the table created at
> the current transaction) need to be WAL-logged while COPY can be
> optimized. If no WAL records are generated on that table, the problem
> we're talking about seems not to occur. Also this seems safe and
> doesn't degrade the performance of data loading. Thought?
Skipping WAL logging means that you need to scan through the whole
shrared buffers to write out dirty buffers and fsync the segments. A
single insert wal record is a couple orders of magnitudes cheaper than
that. Essentially doing this juts for COPY is a heuristic.
--
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To: pgsql-hackers@postgresql.org
Cc: andres@anarazel.de, masao.fujii@gmail.com, tgl@sss.pgh.pa.us, kleptog@svana.org
Subject: Re: WAL logging problem in 9.4.3?
In-Reply-To: <20150710102902.GL340@alap3.anarazel.de>
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