why does this query not use a parallel query - Mailing list pgsql-performance

explain analyze SELECT minion_id FROM mob_player_mob_118 WHERE player_id = 55351078;

                                                                             QUERY PLAN

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 Index Only Scan using mob_player_mob_118_pkey on mob_player_mob_118  (cost=0.44..117887.06 rows=4623076 width=4) (actual time=0.062..3716.105 rows=4625123 loops=1)

   Index Cond: (player_id = 55351078)

   Heap Fetches: 1152408

 Planning time: 0.241 ms

 Execution time: 5272.171 ms

If I just get the count it will use a parallel query

explain analyze SELECT count(minion_id) FROM mob_player_mob_118 WHERE player_id = 55351078;

Thanks