Re: [HACKERS] Partial match fix for fast scan

2014-04-10 Thread Fabrízio de Royes Mello
On Thu, Apr 10, 2014 at 11:09 AM, Alexander Korotkov
aekorot...@gmail.comwrote:

 Hi,

 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(1,100) 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
 while.


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


Regards,

-- 
Fabrízio de Royes Mello
Consultoria/Coaching PostgreSQL
 Timbira: http://www.timbira.com.br
 Blog sobre TI: http://fabriziomello.blogspot.com
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Re: [HACKERS] Partial match fix for fast scan

2014-04-10 Thread Alexander Korotkov
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
  wrote:

 Hi,

 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(1,100) 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
 while.


 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.

--
With best regards,
Alexander Korotkov.


Re: [HACKERS] Partial match fix for fast scan

2014-04-10 Thread Heikki Linnakangas

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

wrote:



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(1,100) 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
while.



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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