Date: Mon, 21 May 2018 04:13:20 -0700 (MST)
From: pavan95 <pavan.postgresdba@gmail.com>
To: pgsql-performance@postgresql.org
Message-ID: <1526901200599-0.post@n3.nabble.com>
In-Reply-To: <1526889830358-0.post@n3.nabble.com>
References: <1526883356469-0.post@n3.nabble.com>
 <1526889830358-0.post@n3.nabble.com>
Subject: Re: Help me in reducing the CPU cost for the high cost query below,
 as it is hitting production seriously!!
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Hi mlunon,

A great thanks for your timely response. And yes it worked when I rewritten
the query.

The query got enhanced with approximate of 1000 planner seeks. You can find
it from the explain plan below:

amp_test=# explain select
sum (
CASE MOD(cast(effort_hours as decimal),1)
        WHEN 0.45 THEN cast(effort_hours as int)+0.75
        WHEN 0.15 THEN cast(effort_hours as int)+0.25
        WHEN 0.30 THEN cast(effort_hours as int)+0.5
        WHEN 0 THEN cast(effort_hours as int)
END
)
from tms_timesheet_details detail , tms_wsr_header header  where
wsr_header_id=header.id and work_order_no != 'CORPORATE';
                                           QUERY PLAN
------------------------------------------------------------------------------------------------
 Aggregate  (cost=8813.60..8813.61 rows=1 width=8)
   ->  Hash Join  (cost=608.27..5647.67 rows=70354 width=8)
         Hash Cond: (detail.wsr_header_id = header.id)
         ->  Seq Scan on tms_timesheet_details detail  (cost=0.00..3431.14
rows=72378 width=12)
               Filter: ((work_order_no)::text <> 'CORPORATE'::text)
         ->  Hash  (cost=399.23..399.23 rows=16723 width=4)
               ->  Seq Scan on tms_wsr_header header  (cost=0.00..399.23
rows=16723 width=4)
(7 rows)


But is this the optimum, can we reduce the cost more at least to around 5000
planner seeks. As it is only a subpart of the query which is called multiple
number of times in the main query.

And to send the main query along with tables description and explain plan it
will be a vast message so send you a sub-part.

Please help me to tune it more. Thanks in Advance.

Regards,
Pavan


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