Re: I: About "Our CLUSTER implementation is pessimal" patch - Mailing list pgsql-hackers

From Heikki Linnakangas
Subject Re: I: About "Our CLUSTER implementation is pessimal" patch
Date
Msg-id 4B72AB00.50902@enterprisedb.com
Whole thread Raw
In response to Re: I: About "Our CLUSTER implementation is pessimal" patch  (Leonardo F <m_lists@yahoo.it>)
Responses Re: I: About "Our CLUSTER implementation is pessimal" patch
Re: I: About "Our CLUSTER implementation is pessimal" patch
List pgsql-hackers
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


pgsql-hackers by date:

Previous
From: Federico Di Gregorio
Date:
Subject: Re: About psycopg2 (by its author)
Next
From: Leonardo F
Date:
Subject: Re: I: About "Our CLUSTER implementation is pessimal" patch