Re: Parallel hints in PostgreSQL with consistent perfromance

[mohini mane <mohini.android@xxxxxxxxx>]

On Thu, Jan 4, 2024 at 7:13 AM Jeff Janes <jeff.janes@xxxxxxxxx> wrote:

 

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.

  >> Thanks Jeff for the response !   It worked with "A" alias 

Cheers,

Jeff