Re: [HACKERS] pg_upgrade may be mortally wounded

> Cached copies of system tables obviously are no problem, since
> pg_upgrade doesn't overwrite those.  I'm concerned whether there can
> be cached copies of pages from user tables or indexes.  Since we've
> just done a bunch of CREATE INDEXes (and a VACUUM, if my latest hack
> is right), it seems at least possible that this would happen.
> 
> Now all those user tables will be empty (zero-length files), so there is
> nothing to cache.  But the user indexes are *not* zero-length --- it looks
> like they are at least 2 pages long even when empty.  So there seems
> to be a real risk of having a cached copy of one of the pages of a user
> index while pg_upgrade is overwriting the index file with new data...

Oh, I see.  That would be a problem.

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