Re: Query Performance

Ron <ronljohnsonjr@xxxxxxxxx> · Sat, 17 Sep 2022 03:48:48 -0500



    On 9/17/22 00:28, sivapostgres@xxxxxxxxx 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.