On Tue, Apr 08, 2003 at 12:29:00AM -0400, Neil Conway wrote:
> > I know in other RDBMS's it's very useful to
> > have index covering because it eliminates needing to load the base pages
> > into memory at all
>
> Storing visibility information in index entries (in addition to heap
> tuples) doesn't strike me as a good idea: for one thing, an
> UPDATE/DELETE would require touching both heap tuples and any index
> entries that point to them. It would also bloat the size of indexes.
True, though these could require touching the indexes anyway due to the
data changes (or at least I assume so, given how other RDBMS's work). It
might be a useful option to allow; in certain situations this could
provide fairly substantial gains, depending on how fat the index is
compared to the raw data rows.
It might also be worth allowing for a dirty read option if you don't
care about transactions that are in progress.
--
Jim C. Nasby (aka Decibel!) jim@nasby.net
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