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

From: Leonardo F <m_lists(at)yahoo(dot)it>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: I: About "Our CLUSTER implementation is pessimal" patch
Date: 2010-02-10 13:24:33
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
> I think you're confusing HeapTuple and HeapTupleHeader. SortTuple->tuple
> field should point to a HeapTupleHeader, not a HeapTuple.

Mmh, I don't get it: that would mean I might be using more info than required,
but I still don't understand why it's not working... at the end, CLUSTER is going
to need full HeapTuple(s) (if I'm not mistaken).
SortTuple->tuple can be any of MinimalTuple, IndexTuple, even a Datum.
So I added my own read/write_rawtuple (I'm not that good, they were in the
original patch and I copy&pasted them).

I can write and read those tuples (using some Asserts I think everything goes

as expected in write/readtup_rawheap). But when calling tuplesort_getrawtuple,
after some "right" tuples, the call to tuplesort_gettuple_common fails because
the lines:

/* pull next preread tuple from list, insert in heap */
newtup = &state->memtuples[tupIndex];

give a wrong initialized "newtup" (in other words, newtup is random memory).
Since write/readtup_rawheap seems fine, I can't understand what's going on...

I write the HeapTuples with:

(in writetup_rawheap):
HeapTuple    tuple = (HeapTuple) stup->tuple;
tuple->t_len += HEAPTUPLESIZE; /* write out the header as well */

LogicalTapeWrite(state->tapeset, tapenum,
 				      tuple, HEAPTUPLESIZE);
LogicalTapeWrite(state->tapeset, tapenum, tuple->t_data, 

then I read them with:
(in readtup_rawheap):
HeapTuple    tuple = (HeapTuple) palloc(tuplen);
USEMEM(state, GetMemoryChunkSpace(tuple));

tuple->t_len = tuplen - HEAPTUPLESIZE;
if (LogicalTapeRead(state->tapeset, tapenum, &tuple->t_self, 
          HEAPTUPLESIZE-sizeof(tuplen)) != HEAPTUPLESIZE-sizeof(tuplen))
          elog(ERROR, "unexpected end of data");
if (LogicalTapeRead(state->tapeset, tapenum, tuple->t_data, tuple->t_len) != tuple->t_len)
          elog(ERROR, "unexpected end of data");


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Subject: Re: Some belated patch review for "Buffers" explain analyze patch
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Subject: Re: I: About "Our CLUSTER implementation is pessimal" patch

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