indexes, then it must use operator number so-and-so for equality.  But
there are lots of GiST opclasses that don't include equality at all; we
can't break that case.


There is a GiST support function for equality of keys, in btree_gist it's named as gbt_*_same. Equality function has support number 7 and is used for stored keys.

But the real issue in unique GiST index is unique :). First, the algorithm of insertion doesn't compare indexed keys on leaf page at all. Values on the same page are compared only when page is splitting (picksplit support method). Second, GiST implementation supports only unordered trees (btree_gist is a some kind of emulation) and it cannot guarantee that equal keys will be close in index. That's related to picksplit and gistpenalty method problem/optimization and data set.

--
Teodor Sigaev                                   E-mail: [EMAIL PROTECTED]
                                                   WWW: http://www.sigaev.ru/

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