Gather  (cost=1000.57..708213.47 rows=599273 width=34) (actual time=0.598..2202.731 rows=656324 loops=1)
   Workers Planned: 4
   Workers Launched: 4
   Buffers: shared hit=3296018 read=262261
   ->  Nested Loop  (cost=0.56..647286.17 rows=149818 width=34) (actual time=0.127..2101.260 rows=131265 loops=5)
         Buffers: shared hit=3296018 read=262261
         ->  Parallel Seq Scan on "AO_8542F1_IFJ_OBJ_ATTR" oa  (cost=0.00..423521.28 rows=150508 width=8) (actual time=0.070..1007.676 rows=131265 loops=5)
               Filter: ("OBJECT_TYPE_ATTRIBUTE_ID" = ANY ('{529,10,506,143}'::integer[]))
               Rows Removed by Filter: 7891993
               Buffers: shared hit=10822 read=262261
         ->  Index Scan using index_ao_8542f1_ifj228666017 on "AO_8542F1_IFJ_OBJ_ATTR_VAL" oav  (cost=0.56..1.48 rows=1 width=42) (actual time=0.008..0.008 rows=1 loops=656324)
               Index Cond: ("OBJECT_ATTRIBUTE_ID" = oa."ID")
               Buffers: shared hit=3285196
 Planning time: 0.431 ms
 Execution time: 2225.289 ms
(15 rows) 

                                   Table "public.AO_8542F1_IFJ_OBJ_ATTR"
          Column          |  Type   |                               Modifiers
--------------------------+---------+-----------------------------------------------------------------------
 ID                       | bigint  | not null default nextval('"AO_8542F1_IFJ_OBJ_ATTR_ID_seq"'::regclass)
 OBJECT_ID                | integer |
 OBJECT_TYPE_ATTRIBUTE_ID | integer |
 UPDATED                  | bigint  |
Indexes:
    "AO_8542F1_IFJ_OBJ_ATTR_pkey" PRIMARY KEY, btree ("ID")
    "index_ao_8542f1_ifj268009346" btree ("OBJECT_TYPE_ATTRIBUTE_ID")
    "index_ao_8542f1_ifj43488772" btree ("OBJECT_ID")
    "index_ao_insight_2" btree ("ID") WHERE "OBJECT_TYPE_ATTRIBUTE_ID" = ANY (ARRAY[529, 10, 506, 143])
Foreign-key constraints:
    "fk_ao_8542f1_ifj_obj_attr_object_id" FOREIGN KEY ("OBJECT_ID") REFERENCES "AO_8542F1_IFJ_OBJ"("ID")
    "fk_ao_8542f1_ifj_obj_attr_object_type_attribute_id" FOREIGN KEY ("OBJECT_TYPE_ATTRIBUTE_ID") REFERENCES "AO_8542F1_IFJ_OBJ_TYPE_ATTR"("ID")
Referenced by:
    TABLE ""AO_8542F1_IFJ_OBJ_ATTR_VAL"" CONSTRAINT "fk_ao_8542f1_ifj_obj_attr_val_object_attribute_id" FOREIGN KEY ("OBJECT_ATTRIBUTE_ID") REFERENCES "AO_8542F1_IFJ_OBJ_ATTR"("ID")

 
              total        used        free      shared  buff/cache   available
Mem:          24947        2118         207        5803       22620       16659
Swap:          3071           0        3071
Total:        28019        2118        3279 

max_wal_size = 4GB
min_wal_size = 1GB
checkpoint_completion_target = 0.7
effective_io_concurrency = 200          # 1-1000; 0 disables prefetching
max_worker_processes = 8                # (change requires restart)
max_parallel_workers_per_gather = 4
work_mem = 8987kB
maintenance_work_mem = 1408MB
shared_buffers = 6240MB

with max_salary_table as (
    SELECT Employee.name,
           D.name as name_company,
           Employee.salary,
           dense_rank() OVER (PARTITION BY Employee.departmentId order by salary DESC) as rating
    from Employee
             join Department D on D.id = Employee.departmentId
)
select name, name_company, salary
from max_salary_table
where rating = 1;