Re: [PATCH] Covering SPGiST index

I have a wild idea of renaming nextOffset in SpGistLeafTupleData.
Or at least documenting in comments that this field is more than just an offset.

This looks like assert rather than real runtime check in spgLeafTupleSize()

+               if (state->includeTupdesc->natts + 1 >= INDEX_MAX_KEYS)
+                       ereport(ERROR,
+                                       (errcode(ERRCODE_TOO_MANY_COLUMNS),
+                                        errmsg("number of index columns (%d) exceeds limit (%d)",
+                                                       state->includeTupdesc->natts, INDEX_MAX_KEYS)));
Even if you go with check, number of columns is state->includeTupdesc->natts  + 1.

Also I'd refactor this
+       /* Form descriptor for INCLUDE columns if any */