From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Drazen Kacar <drazen(dot)kacar(at)oradian(dot)com> |
Cc: | pgsql-admin(at)postgresql(dot)org |
Subject: | Re: Zeroed out pages at the end of the database files |
Date: | 2013-10-30 16:48:40 |
Message-ID: | 4981.1383151720@sss.pgh.pa.us |
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Lists: | pgsql-admin |
Drazen Kacar <drazen(dot)kacar(at)oradian(dot)com> writes:
> It turned out that pg_filedump reported errors for 34 database files, but
> that was because all those files had one or more database pages (8k) at the
> end of the file zeroed out.
This can definitely happen after a database crash; it's not a problem
since the wasted space will be recovered by VACUUM.
I don't recall at the moment if there are any code paths that can cause
it without a crash. However, if you're looking directly at the disk
files it's definitely possible for there to be zeroes in a page that
has been obtained from the OS but never yet flushed out of shared
buffers.
regards, tom lane
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