Re: page corruption on 8.3+ that makes it to standby

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>, Jeff Davis <pgsql@j-davis.com>, pgsql-hackers@postgresql.org
Date: 2010-07-28T19:37:49Z
Lists: pgsql-hackers
I wrote:
>>> I think it is appropriate to be setting the LSN/TLI in the case of a
>>> page that's been constructed by the caller as part of the WAL-logged
>>> action, but doing so in copy_relation_data seems rather questionable.

BTW, I thought of an argument that explains why that's sane: it marks
the copied page as having been recently WAL-logged.  If we do some
action on the copied relation shortly after completing the
copy_relation_data transaction, we will see that its LSN is later than
the last checkpoint and know that we don't need to emit a full-page WAL
image for it, which is correct because in case of crash+restart the
HEAP_NEWPAGE record will provide the full-page image.  If we left the
source relation's page's LSN in there, we would frequently make the
wrong decision and emit an unnecessary extra full-page image.

So nevermind that distraction.  I'm back to thinking that fix1 is
the way to go.

			regards, tom lane