Greetings, * Fabien COELHO (coe...@cri.ensmp.fr) wrote: > >Note that a short read isn't an error and falls under the 'new' blocks > >discussion above. > > I'm really unsure that a short read should really be coldly skipped: > > If the check is offline, then one file is in a very bad state, this is > really a panic situation.
Why? Are we sure that's really something which can't ever happen, even if the database was shutdown with 'immediate'? I don't think it can but that's something to consider. In any case, my comments were specifically thinking about it from an 'online' perspective. > If the check is online, given that both postgres and the verify command > interact with the same OS (?) and at the pg page level, I'm not sure in > which situation there could be a partial block, because pg would only send > full pages to the OS. The OS doesn't operate at the same level that PG does- a single write in PG could get blocked and scheduled off after having only copied half of the 8k that PG sends. This isn't really debatable- we've seen it happen and everything is operating perfectly correctly, it just happens that you were able to get a read() at the same time a write() was happening and that only part of the page had been updated at that point. Thanks! Stephen
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