SP-GiST bug.

Hi!

create table xxx ( t text);

insert into xxx select 'x' || v::text from generate_series(1, 291) as v;
insert into xxx values ('');

create index xxxidx on xxx using spgist (t);

And postgres will eat memory forever. It seems to me that checkAllTheSame
wrongly decides that all tuples are the same. All tuples except tuple to be
inserted have the same character 'x' and only new tuple has '\0'. But
checkAllTheSame() removes new tuple because set of tuples is too big to fit page
and founds that all tuples are the same. Patch attached, suppose, all branches
with spgist should be fixed.

Original data is too big to send in e-mail list or even send link, and the bug
caused not in root page as in example above.

--
Teodor Sigaev E-mail: teodor(at)sigaev(dot)ru
WWW: http://www.sigaev.ru/