On Tue, 2006-06-06 at 10:59 -0400, Tom Lane wrote: > Simon Riggs <[EMAIL PROTECTED]> writes: > > Why do we have a WAL record for CLOG page extension? > > Think of it as being a substitute for a full-page image, or perhaps the > init-bit in heap-insert records is the closest analogy. Your patch is > unworkable because it provides no means for recovering from > corrupt-on-disk clog pages.
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The current system only helps recover from corrupt-on-disk pages that have been newly written since last checkpoint (or maybe two checkpoints ago). If the pages were initialised before that then we've simply lost that data altogether anyhow. Seems like we're writing WAL for a fairly rare situation, yet we still have some big issues. Should we hold two copies of the clog for robustness? That way we can just switch to the second copy if we have problems. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
