Re: Query Performance

On 9/17/22 00:28, sivapostgres(at)yahoo(dot)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?

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