Re: weired behavior... after pg_resetxlog-> dump->initdb-->reload.

Tom Lane wrote:

>Rajesh Kumar Mallah <mallah(at)trade-india(dot)com> writes:
>
>
>>It does.
>>
>>
>
>And?
>
>
>
Yep the problem of original posting could be replicated on
disabling hash aggregates. On disabling i could get the repeated rows.

Regds
Mallah.

rt2=# SET enable_hashagg TO off;
SET
Time: 329.533 ms
rt2=# explain analyze SELECT name from users_sample group by name having
count(*) > 1 ;
+------------------------------------------------------------------------------------------------------------------------------+
| QUERY
PLAN |
+------------------------------------------------------------------------------------------------------------------------------+
| GroupAggregate (cost=69.83..78.33 rows=200 width=78) (actual
time=2411.411..2749.733 rows=4 loops=1) |
| Filter: (count(*) >
1)
|
| -> Sort (cost=69.83..72.33 rows=1000 width=78) (actual
time=2411.300..2532.821 rows=100489 loops=1) |
| Sort Key:
name
|
| -> Seq Scan on users_sample (cost=0.00..20.00 rows=1000
width=78) (actual time=0.024..170.258 rows=100489 loops=1) |
| Total runtime: 2915.439
ms
|
+------------------------------------------------------------------------------------------------------------------------------+
(6 rows)

Time: 3265.102 ms
rt2=# SELECT name from users_sample group by name having count(*) > 1 ;
+----------------------+
| name |
+----------------------+
| ??? |
| ????163.com |
| ?(at)hotmail(dot)com |
| p? |
+----------------------+
(4 rows)

Time: 3358.030 ms
rt2=# SET enable_hashagg TO on;
SET
Time: 330.148 ms
rt2=# SELECT name from users_sample group by name having count(*) > 1 ;
+------+
| name |
+------+
+------+
(0 rows)

Time: 752.395 ms
rt2=#

>>Tom Lane wrote:
>>
>>
>>>Hm. Does EXPLAIN show that the GROUP BY query is using hash
>>>aggregation? Does its behavior change if you turn off enable_hashagg?
>>>
>>>
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> regards, tom lane
>
>
>