Re: page is uninitialized --- fixing

On Tue, 2009-06-09 at 17:28 -0400, Tom Lane wrote:
> Simon Riggs <simon@2ndQuadrant.com> writes:
> > A corrupt record of a block number would do this in XLogReadBuffer() if
> > we had full page writes enabled. But it would have to be corrupt between
> > setting it correctly and the CRC check on the WAL record. Which is a
> > fairly small window of believability.
> 
> > Should there be a sanity check on how far a relation can be extended in
> > recovery?
> 
> As you say, that's not a highly believable theory.  I'd prefer not to
> put an arbitrary limit into the recovery code unless we can positively
> pin this down as the source of the problem.
> 
> Is there any particular reason to suppose that the empty pages appeared
> during a crash recovery?

Probably because my Rorschach tests all look like database recoveries.

> Have you read through md.c?  I seem to recall there are some slightly
> squirrelly choices made there about segment-extension behavior.  Maybe
> it could've done the wrong thing here during normal operation.

Yes, but will do again if you think I should check.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support