On Thu, Aug 18, 2016 at 1:41 PM, Claudio Freire <klaussfre...@gmail.com> wrote:
> In fact, that's why non-leaf index tuples need a different format,
> because while leaf index tuples contain the heap pointer already,
> non-leaf ones contain only the downlink, not the pointer into the
> heap. To be able to do comparisons and pick the right downlink, the
> original heap pointer in the leaf index tuple is copied into the
> downlink index tuple when splitting pages into an additional
> IndexTupleData header that is prepended only to non-leaf index tuples.

I think that this is a bad idea. We need to implement suffix
truncation of internal page index tuples at some point, to make them
contain less information from the original leaf page index tuple.
That's an important optimization, because it increases fan-in. This
seems like a move in the opposite direction.

ISTM that the way to address this problem is with a duplicate list
and/or prefix compression in leaf pages.

Peter Geoghegan

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