Jeff, On 11/12/2012 06:52 PM, Jeff Davis wrote: > OK, so here's my proposal for a first patch (changes from Simon's > patch): > > * Add a flag to the postgres executable indicating that it should use > checksums on everything. This would only be valid if bootstrap mode is > also specified. > * Add a multi-state checksums flag in pg_control, that would have > three states: OFF, ENABLING, and ON. It would only be set to ON during > bootstrap, and in this first patch, it would not be possible to set > ENABLING. > * Remove GUC and use this checksums flag everywhere. > * Use the TLI field rather than the version field of the page header. > * Incorporate page number into checksum calculation (already done). > > Does this satisfy the requirements for a first step? Does it interfere > with potential future work?
As described before in this thread, I think we might be able to do without the "has checksum"-bit, as yet another simplification. But I don't object to adding it, either. > It's slightly better than that. It's more like: "we can tell you if any > of your data gets corrupted after transaction X". If old data is > corrupted before transaction X, then there's nothing we can do. But if > it's corrupted after transaction X (even if it's old data), the > checksums should catch it. I (mis?)read that as Greg referring to the intermediate (enabling) state, where pages with old data may or may not have a checksum, yet. So I think it was an argument against staying in that state any longer than necessary. Regards Markus Wanner -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
