Re: Re: GiST optimizing memmoves in gistplacetopage for fixed-size updates [PoC]

Here is BRIN-compatible version of patch. Now function
PageIndexTupleOverwrite consumes tuple size as a parameter, this
behavior is coherent with PageAddItem.
Also, i had to remove asserstion that item has a storage in the loop
that adjusts line pointers. It would be great if someone could check
that place (commented Assert(ItemIdHasStorage(ii)); in
PageIndexTupleOverwrite). I suspect that there might be a case when
linp's should not be adjusted.

Best regards, Andrey Borodin, Octonica & Ural Federal University.