Re: GiST seems to drop left-branch leaf tuples

From: Peter Tanski <ptanski(at)raditaz(dot)com>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: GiST seems to drop left-branch leaf tuples
Date: 2010-11-23 16:39:33
Message-ID: 0B1250AB-55F8-4475-9A0B-982B567A923B@raditaz.com
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Picksplit() seems to be an exceptional case here: the first and last
numbers in entryvec are invalid so

entryvec->vector[entryvec->n - 1]

is invalid. All the other GiST code Picksplit() functions use the
same convention. For example, see the btree_gist picksplit function, at
http://doxygen.postgresql.org/btree__utils__num_8c-source.html#l00241

OffsetNumber i,
maxoff = entryvec->n - 1;

On Nov 23, 2010, at 10:22 AM, Alvaro Herrera wrote:

> Excerpts from Peter Tanski's message of mar nov 23 12:00:52 -0300
> 2010:
>
>> There are checks inside the Picksplit() function for the number of
>> entries:
>>
>> OffsetNumber maxoff = entryvec->n - 1;
>> int n_entries, j;
>> n_entries = Max(maxoff, 1) - 1;
>>
>> j = 0;
>> for (i = FirstOffsetNumber; i < maxoff; i = OffsetNumberNext(i)) {
>> FPrint* v = deserialize_fprint(entv[i].key);
>
> Isn't this off by one? Offset numbers are 1-based, so the maxoff
> computation is wrong.
>
> --
> Álvaro Herrera <alvherre(at)commandprompt(dot)com>
> The PostgreSQL Company - Command Prompt, Inc.
> PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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