Re: Query Performance - Mailing list pgsql-general

From Ron
Subject Re: Query Performance
Date
Msg-id ab198555-1b4a-521f-d5a1-2674852b5e35@gmail.com
Whole thread Raw
In response to Re: Query Performance  ("sivapostgres@yahoo.com" <sivapostgres@yahoo.com>)
List pgsql-general
On 9/17/22 00:28, sivapostgres@yahoo.com wrote:
Hello,

My query is like this   

Select a.field1, a.field2, a.field3
From   (Select a.field1, b.field2, c.field3
        From   table1 a
        Join   table2 b
        on     b.something = a.something
        Join   table3 c
        On     c.something = a.something 
        Where  a.field7 = 'value'

        UNION ALL

        Select a.field4, a.field5, a.field6
        From   table11 a
        Join   table21 b
        On     b.something = a.something
        Where  a.field8 = 'something' ) a
Join   table10 b
On     b.field11 = (Select c.field11
                    From   table10 c
                    Where  c.field10 = a.field1 )                     <- instead of a.field1, if I hardcode value (eg. '100') query runs faster
Join   table21 c
On     c.something = a.something
...


In the above query, If I substitute a value for a.field1, query runs faster.   
Any suggestion/guidance/links to improve the query performance without substituting the value ?

Is there an index on table1.field1?
Have you vacuumed or analyzed table1 lately?
Have you decomposed the query into the smallest possible query that demonstrates the problem?


--
Angular momentum makes the world go 'round.

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