Tom Lane wrote:
> Jean-Paul ARGUDO <jean-paul(dot)argudo(at)IDEALX(dot)com> writes:
> > Since my english is not so fluent, I found on the net a little
> > explication about Reverse Key Indexes (not RTREE, sorry :).
> > As an explication, you could read there the point 9 :
> > http://oracle.oreilly.com/news/oraclepp_0900.html
> > ... Reverse key indexes reverse the
> > bytes in each index entry, causing
> > sequential entries to be dispersed across the
> > index tree.
> Hmm. I think you could implement that with a custom index opclass
> consisting of operators that flipped the bytes before comparison.
> Not clear that it'd really buy you enough to be worth the trouble,
> but if someone wants to try it...
> > ... One
> > trade-off involved with using this
> > technique is that by its nature, reverse key indexes
> > cannot be used as the basis for an index
> > range scan.
> The way this would show up in Postgres is that you would use the
> standard integer = operator as the = member of the opclass, but
> all the other members would be byte-reversed-comparison operators
> that would never be useful in real-world queries.
Never is too strong word. I guess that if index block contention is
serious enough problem for insert-intensive aplication and you need
only = access then this could be a good thing.
OTOH it will probably be not so good for cache usage and update
locality so it may not be as good as it sounds even for the above
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