From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com>, Jeff Davis <pgsql(at)j-davis(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: page corruption on 8.3+ that makes it to standby |
Date: | 2010-07-28 19:37:49 |
Message-ID: | 21699.1280345869@sss.pgh.pa.us |
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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
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