On 04/10/2014 10:00 PM, Alexander Korotkov wrote:
On Thu, Apr 10, 2014 at 8:22 PM, Fabrízio de Royes Mello <
fabriziome...@gmail.com> wrote:

On Thu, Apr 10, 2014 at 11:09 AM, Alexander Korotkov <aekorot...@gmail.com

GIN partial match appears to be broken after fast scan. Following simple
test case raises assertion failure.

create extension btree_gin;
create table test as (select id, random() as val from
generate_series(1,1000000) id);
create index test_idx on test using gin (val);
vacuum test;
select * from test where val between 0.1 and 0.9;

Attached patch fixes bugs in entryGetItem function.
I would especially point that "continue;" checks "while" condition even
if it's postfix "while". That's why I surrounded tbm_iterate with another

Interesting... to me (using current master) your test case doesn't fail...

fabrizio=# select * from test where val between 0.1 and 0.9;
    id   |        val
       1 | 0.554413774050772
       2 | 0.767866868525743
       3 | 0.601187175605446

But fail if I change the values of between clause:

fabrizio=# select * from test where val between 0.1 and 0.19;
ERROR:  tuple offset out of range: 8080

It must be compiled with --enable-cassert to fail on assertion.

I'm actually getting the "tuple offset out of range" with Fabrizio's query, even after your fix (not every time, run it a few times, launching a new connection each time). So there's another bug lurking there. The problem seems to be that even though we've checked in the innermost loop that not all of the items on the page are <= advancePast, that situation can change later if advancePast is advanced. So on next invocation entryGetItem, the loop to skip past advancePast might read bogus offsets in the array.

I pushed a patch, which includes Alexander's fix, and also fixes the second issue.

- Heikki

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