Re: Index AM change proposals, redux

"Zeugswetter Andreas OSB SD" <Andreas.Zeugswetter@s-itsolutions.at> writes:
>> ... The really serious problem I've got with it is that
>> it'd foreclose the possibility of returning actual index keys from btree
>> indexes, thus basically killing the usefulness of that idea.  I'm not
>> convinced it would offer enough gain to be worth paying that price.

> I do not see the serious problem ? The one key that is stored would 
> represent all tuples it points to.

No, the entry represents a range of values for which the one key is the
lower bound.  You don't know just what the keys are for the other
tuples, unless you go to the heap and look.

We could restrict GIT to only represent tuples with exactly the same
key, but that takes away a whole lot of its use-case (especially so
now that HOT is in there).
        regards, tom lane