Re: CREATE INDEX and HOT - revised design

Bruce Momjian wrote:
> Bruce Momjian wrote:
> > > Also, I am wondering whether the information that which index is used to
> > > fetch a tuple is always available. I haven't checked, but do we have that
> > > information in lossy bitmap heapscan ?
> >
> > Oh, that is an interesting problem because an index might have one index
> > entry representing an entire HOT chain, while another index might
> > represent each chain member by individual index entries. When we do the
> > bitmaps, don't we access them by heap tid, meaning we would find all
> > entries anyway?
>
> I thinking some more, it would be a problem because while we are merging
> the tids, we are using index entries and haven't looked at the heap yet.
> I am guessing we would have to exclude the new index from bitmap joins
> with other indexes until the VACUUM happens.

Thinking some more, bitmap scans have a mode that tracks just the page
numbers, rather than the tids --- if the index visibilities do not
match, we would need to fall back to that mode.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://www.enterprisedb.com

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