Re: [ADMIN] OUTER JOIN IS SLOW - Mailing list pgsql-general

Just to make things more clear I ran EXPLAIN ANALYZE on the slow query.
I got

Merge Full Join  (cost=62.33..73.36 rows=1000 width=19) (actual
time=39.205..8521.644 rows=272 loops=1)
   Merge Cond: ("outer".pkey = "inner".d1)
   ->  Index Scan using mutualfd_weekday_qbid_pkey_idx on
mutualfd_weekday_qbid  (cost=0.00..6.01 rows=1 width=19) (actual
time=34.579..8510.801 rows=253 loops=1)
         Index Cond: ((pkey >= '2005-12-15'::date) AND (pkey <=
'2006-12-15'::date))
         Filter: (cusip = '92193920'::text)
   ->  Sort  (cost=62.33..64.83 rows=1000 width=4) (actual
time=4.604..5.674 rows=262 loops=1)
         Sort Key: d1.d1
         ->  Function Scan on "getDateRange" d1  (cost=0.00..12.50
rows=1000 width=4) (actual time=2.591..3.591 rows=262 loops=1)
Total runtime: 8522.894 ms
(9 rows)

It looks like this line:

"->  Index Scan using mutualfd_weekday_qbid_pkey_idx on
mutualfd_weekday_qbid  (cost=0.00..6.01 rows=1 width=19) (actual
time=34.579..8510.801 rows=253 loops=1)"

is the problem.  As I understand it is using the index but it is low as
dirt.  Hopefully, the -z will fix this.  I also ran the same query but
with earlier dates in the table and the query ran much faster.

Merge Full Join  (cost=3492.48..3505.60 rows=1034 width=19) (actual
time= 7.605..12.851 rows=273 loops=1)
   Merge Cond: ("outer".d1 = "inner".pkey)
   ->  Sort  (cost=62.33..64.83 rows=1000 width=4) (actual
time=4.586..5.530 rows=263 loops=1)
         Sort Key: d1.d1
         ->  Function Scan on "getDateRange" d1  (cost=0.00..12.50
rows=1000 width=4) (actual time=2.493..3.515 rows=263 loops=1)
   ->  Sort  (cost=3430.15..3432.74 rows=1034 width=19) (actual
time=2.998..3.971 rows=263 loops=1)
         Sort Key: mutualfd_weekday_qbid.pkey
         ->  Index Scan using mutualfd_weekday_qbid_pkey on
mutualfd_weekday_qbid  (cost=0.00..3378.38 rows=1034 width=19) (actual
time=0.075..1.843 rows=263 loops=1)
               Index Cond: ((cusip = '92193920'::text) AND (pkey >=
'1999-12-15'::date) AND (pkey <= '2000-12-15'::date))
Total runtime: 13.935 ms
(10 rows)

In this case it only took 13.935ms as compared to 8522.894 ms for the
newer data.

Benjamin

Shoaib Mir wrote:
> ....adding to the last email, for now try the work_mem but you should
> be adding ANALYZE along with the VACUUM (with a cron job I guess) you
> do regularly.
>
> ------------
> Shoaib Mir
> EntperpriseDB ( www.enterprisedb.com <http://www.enterprisedb.com>)
>
> On 12/24/06, *Shoaib Mir* <shoaibmir@gmail.com
> <mailto: shoaibmir@gmail.com>> wrote:
>
>     Try increasing the work_mem first to see the change, that might help.
>
>     -------------
>     Shoaib Mir
>     EnterpriseDB ( www.enterprisedb.com <http://www.enterprisedb.com>)
>
>     On 12/24/06, *Benjamin Arai* <benjamin@araisoft.com
>     <mailto:benjamin@araisoft.com>> wrote:
>
>         I have been running pieces of my PL function by hand and I
>         have found
>         that the following queries work by themselves taking less than
>         a second
>         to execute.
>
>         getDateRange"('12/1/2005','12/1/2006')  <- simply generates a
>         date
>         list.  Doesn't even access a table
>
>         SELECT * FROM mutualfd_weekday_qbid WHERE cusip='92193920'
>         AND  pkey >=
>         '12/15/2005' AND pkey <= '12/15/2006';
>
>         But when combined as below it takes 10 seconds to execute.
>
>         SELECT d1 as date, d2.data as data FROM
>         "getDateRange"('12/1/2005','12/1/2006') d1 FULL OUTER JOIN
>         (SELECT *
>         FROM mutualfd_weekday_qbid WHERE cusip='92193920' AND  pkey >=
>         '12/15/2005' AND pkey <= '12/15/2006') d2 ON d1=d2.pkey;
>
>         Do I need to increase the work_mem or is this possible still a
>         ANALYZE
>         issue?
>
>         Benjamin
>
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