From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Dave Stibrany <dstibrany@gmail.com>
Cc: pgsql-admin@postgresql.org
Subject: Re: Does my pg_xlog directory look right?
Date: Fri, 20 May 2016 14:41:26 -0400
Message-ID: <20160520184126.GA333087@alvherre.pgsql> (raw)
In-Reply-To: <54621.1463769300@sss.pgh.pa.us>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-admin>
Tom Lane wrote:
> No, it probably means that neither one has been written at all yet.
> Typically, when a WAL segment is deemed no longer needed, the file isn't
> physically removed but is merely renamed into place as a future segment.
> The idea is to reduce unnecessary filesystem work as we create and delete
> WAL segments. You could check this out if you have pg_xlogdump at hand,
> by seeing whether the WAL file's first page header claims to belong to the
> segment indicated by the file name, or to some much-older segment.
This may be a good time to point out that pg_xlogdump fails completely
when a file's contents does not match the file name, with no indication
about what a better file name would be. In other words, if a file has
been recycled and not written to yet under the new name, it doesn't tell
you anything useful. This is pretty annoying.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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To: pgsql-admin@postgresql.org
Cc: alvherre@2ndquadrant.com, tgl@sss.pgh.pa.us, dstibrany@gmail.com
Subject: Re: Does my pg_xlog directory look right?
In-Reply-To: <20160520184126.GA333087@alvherre.pgsql>
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