On 6/8/2010 8:27 AM, Greg Stark wrote:
On Tue, Jun 8, 2010 at 2:26 AM, Stephen Frost <sfr...@snowman.net> wrote:
Just an off-the-wall thought, but, would it be possible to have a tool
which read WAL backwards and compared entries in the WAL against entries
on disk? I realize that you'd only see one version of a particular
block and then have to skip any updates which are earlier than it, but
it seems like you could cover a pretty large chunk of the recent changes
to the database using this approach..
I assume you mean back out the changes incrementally until you find a
full_page_write and see if it matches? And continue comparing with
full_page_writes once per checkpoint? I don't think the WAL has enough
information to replay backwards though. For example vacuum cleanup
records just list the tids to remove. They don't have the contents to
replace there.
You can't back out changes. WAL does not contain before images.
Jan
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liberty nor security. -- Benjamin Franklin
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