seems similar to this problem:
http://stackoverflow.com/questions/5198380/improving-postgres-psycopg2-query-performance-for-python-to-the-same-level-of-ja
but no solution yet.
On Thu, Jan 12, 2012 at 5:00 PM, Yan Chunlu <springrider@gmail.com> wrote:
> I also tried explain but found nothing special:
>
> explain select * from data_table where thing_id in
> (164438,112478,102941,112377,164442,181764,104028);
> QUERY PLAN
> -------------------------------------------------------------------------------------------------------
> Bitmap Heap Scan on data_table (cost=31.75..579.10 rows=141 width=53)
> Recheck Cond: (thing_id = ANY
> ('{164438,112478,102941,112377,164442,181764,104028}'::bigint[]))
> -> Bitmap Index Scan on idx_data_table (cost=0.00..31.71 rows=141 width=0)
> Index Cond: (thing_id = ANY
> ('{164438,112478,102941,112377,164442,181764,104028}'::bigint[]))
>
>
>
> On Thu, Jan 12, 2012 at 4:47 PM, Yan Chunlu <springrider@gmail.com> wrote:
>> I am transforming a db with millions records to anther schema. for
>> some reason I need to select the records using IN (xx,xx).
>>
>> the ids in the IN was about 1000 recored every time, but I found the
>> query was getting slow while the selection moving on.
>>
>> the shared buffer is 2048M. and the cpu and io usage is as normal.
>>
>> But while I am processing a smaller db on another machine, which only
>> has the default 24MB, the selection went very smooth.
>>
>>
>> here is the logs:
>>
>> start... 0 limit:1000
>> selection time: 0.140721082687
>> sort_options
>> msgtime
>> start... 1000 limit:1000
>> selection time: 0.122759103775
>> start... 2000 limit:1000
>> selection time: 0.150802850723
>> start... 3000 limit:1000
>> selection time: 0.173918008804
>> start... 4000 limit:1000
>> selection time: 0.212812900543
>> start... 5000 limit:1000
>> selection time: 0.255054950714
>> start... 6000 limit:1000
>> selection time: 0.230540037155
>> start... 7000 limit:1000
>> selection time: 0.24426317215
>> start... 8000 limit:1000
>> selection time: 0.326669931412
>> start... 9000 limit:1000
>> selection time: 0.351358175278
>> start... 10000 limit:1000
>> selection time: 0.386382102966
>> start... 11000 limit:1000
>> selection time: 0.440491914749
>> start... 12000 limit:1000
>> selection time: 0.443608045578
>> start... 13000 limit:1000
>> selection time: 0.49751496315
>> start... 14000 limit:1000
>> selection time: 12.0050361156
>> start... 15000 limit:1000
>> selection time: 26.3596658707
>>
>> start... 16000 limit:1000
>> selection time: 43.5269529819