Robert Treat wrote:

It is believed that the IN optimization can lead to faster IN times than
EXIST times on some queries, the extent of which is still a bit of an
unknown. (Incidentally is there an FAQ item on this that needs
updating?)

Thanks every one for clarifying. Its really a nice thing to see IN working
so well becoz its easier to read the SQL using IN.

looks like NOT IN is indifferent to indexes where is IN uses indexes , is it true?

does indexes affect the new manner in which IN works in 7.4 ?

Does the not exist query produce worse results in 7.4 than it did in
7.3?

Will surely post the overvation sometime.

Regards
Mallah.


Robert Treat

On Thu, 2003-11-13 at 02:53, Rajesh Kumar Mallah wrote:

Hi,

NOT EXISTS is taking almost double time than NOT IN .
I know IN has been optimised in 7.4 but is anything 
wrong with the NOT EXISTS?

I have vaccumed , analyze and run the query many times
still not in is faster than exists :>


Regds
Mallah.

NOT IN PLAN

tradein_clients=# explain analyze SELECT  count(*) from general.profile_master where
 profile_id not in (select  profile_id from general.account_profiles ) ;
                                                             QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------
Aggregate  (cost=32238.19..32238.19 rows=1 width=0) (actual time=5329.206..5329.207 rows=1 loops=1)
  ->  Seq Scan on profile_master  (cost=4458.25..31340.38 rows=359125 width=0) (actual time=1055.496..4637.908 rows=470386 loops=1)
        Filter: (NOT (hashed subplan))
        SubPlan
          ->  Seq Scan on account_profiles  (cost=0.00..3817.80 rows=256180 width=4) (actual time=0.061..507.811 rows=256180 loops=1)
Total runtime: 5337.591 ms
(6 rows)


tradein_clients=# explain analyze SELECT  count(*) from general.profile_master where not exists 
(select  profile_id from general.account_profiles where profile_id=general.profile_master.profile_id ) ;

                                                                          QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------------
Aggregate  (cost=1674981.97..1674981.97 rows=1 width=0) (actual time=14600.386..14600.387 rows=1 loops=1)
  ->  Seq Scan on profile_master  (cost=0.00..1674084.16 rows=359125 width=0) (actual time=13.687..13815.798 rows=470386 loops=1)
        Filter: (NOT (subplan))
        SubPlan
          ->  Index Scan using account_profiles_profile_id on account_profiles  (cost=0.00..4.59 rows=2 width=4) (actual time=0.013..0.013 rows=0 loops=718250)
                Index Cond: (profile_id = $0)
Total runtime: 14600.531 ms



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