Re: Parallel hints in PostgreSQL with consistent perfromance

> *1st time query executed with PARALLEL DEGREE 2 *
> explain analyze select /*+* PARALLEL(A 2)* */ * from
> test_compare_all_col_src1 A;
> QUERY
> PLAN
>
> ----------------------------------------------------------------------------------------------------------------------------------------------------
> Gather (cost=10.00..45524.73 rows=949636 width=97) (actual
> time=0.673..173.017 rows=955000 loops=1)
> Workers Planned: 4
> * Workers Launched: 4*
> -> Parallel Seq Scan on test_compare_all_col_src1 a
> (cost=0.00..44565.09 rows=237409 width=97) (actual time=0.039..51.941
> rows=191000 loops=5)
> Planning Time: 0.093 ms
> * Execution Time: 209.745 ms*
> (6 rows)
>

Your alias is not enclosed in double quotes, so it is downcased to "a" (as
can be seen from the alias printed in the plan). But pg_hint_plan hints
don't follow the downcasing convention, so the hint on "A" does not match
the alias "a", and so is ignored.

Cheers,

Jeff

>