Re: I: About "Our CLUSTER implementation is pessimal" patch

Leonardo F wrote:
> static void
> writetup_rawheap(Tuplesortstate *state, int tapenum, SortTuple *stup)
> {
> HeapTuple tuple = (HeapTuple) stup->tuple;

I think you're confusing HeapTuple and HeapTupleHeader. SortTuple->tuple
field should point to a HeapTupleHeader, not a HeapTuple.

The right mental model is that HeapTupleHeader is a physical tuple, one
that you store on disk for example. A HeapTuple is an in-memory wrapper,
or pointer if you will, to a HeapTupleHeader, and holds some additional
information on the tuple that's useful when operating on it.

To add to the confusion, MinimalTuple is a shortened counterpart of
HeapTuple*Header*, not HeapTuple. And SortTuple is an in-memory wrapper
similar to HeapTuple, containing additional information on the tuple
that helps with sorting.

I didn't look at the rest of the code in detail, but I think that's
where your problems are stemming from.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com