Re: [PATCH] Covering SPGiST index

But let's change macro a bit. When I see
SGLT_SET_OFFSET(leafTuple->nextOffset, InvalidOffsetNumber);
I expect that leafTuple->nextOffset is function argument by value and will not be changed.
For example see ItemPointerSetOffsetNumber() - it's not exposing ip_posid.

Also, I'd propose instead of
>*(leafChainDatums + i * natts) and leafChainIsnulls + i * natts
using something like
>int some_index = i * natts;
>leafChainDatumsp[some_index] and &leafChainIsnulls[some_index]
But, probably, it's a matter of taste...

Also I'm not sure would it be helpful to use instead of
>isnull[0] and leafDatum[0]
more complex
>#define SpgKeyIndex 0
>isnull[SpgKeyIndex] and leafDatum[SpgKeyIndex]
There is so many [0] in the patch...