Testing WAL replay by comparing before and after images again

From: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
To: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Testing WAL replay by comparing before and after images again
Date: 2015-09-04 12:45:56
Message-ID: 55E99284.2020107@iki.fi
Views: Raw Message | Whole Thread | Download mbox | Resend email
Lists: pgsql-hackers

I rerun my little testing tool that compares buffer page contents after
every modification, in master and in WAL replay. Previously discussed
here: http://www.postgresql.org/message-id/5357B582.7060707@vmware.com.
Here's an updated version of my original hack, for current git master.
(Michael posted less-hacky versions of that, but unfortunately I haven't
gotten around to review his stuff.)

I did not find any new bugs. There were a couple of false positives
however. Firstly, the post-processing tool needed to be taught that BRIN
pages can have the PD_HAS_FREE_LINES flag set, and ignore that (like it
does for heap and other indexam pages).

Another issue was with the new speculative insertions. Replaying a
speculative insertion record sets the tuple's CTID to point to itself,
like in a regular insertion. But in the original system, the CTID is set
to a special speculative insertion token. The tool flagged up that

I propose the attached patch
(mark-speculative-insertions-in-replay.patch) to fix that in the replay
routine. This is not required for correctness, but helps this tool, and
seems like a good idea for debugging purposes anyway.

Any objections?

- Heikki

Attachment Content-Type Size
mark-speculative-insertions-in-replay.patch text/x-diff 1.2 KB
0001-Write-buffer-image-before-and-after-every-WAL-record.patch text/x-diff 27.6 KB


Browse pgsql-hackers by date

  From Date Subject
Next Message Thomas Munro 2015-09-04 13:21:17 Making tab-complete.c easier to maintain
Previous Message Teodor Sigaev 2015-09-04 12:11:12 Re: [PATCH] Microvacuum for gist.