EXPLAIN (ANALYZE, VERBOSE)
SELECT concod,
       conparnum,
       conpardatven
  FROM contrato c
       JOIN contrato_parcela cp USING (concod)
 WHERE carcod = 100
 GROUP BY 1,2,3
HAVING count(*) > 1

/*************************************************************************************************/

GroupAggregate  (cost=1245097.18..1322824.31 rows=3454539 width=14) (actual time=80350.944..81346.022 rows=86 loops=1)
  Output: c.concod, cp.conparnum, cp.conpardatven
  Group Key: c.concod, cp.conparnum, cp.conpardatven
  Filter: (count(*) > 1)
  Rows Removed by Filter: 6787359
  ->  Sort  (cost=1245097.18..1253733.53 rows=3454539 width=14) (actual time=77979.130..79186.066 rows=6787531 loops=1)
        Output: c.concod, cp.conparnum, cp.conpardatven
        Sort Key: c.concod, cp.conparnum, cp.conpardatven
        Sort Method: external merge  Disk: 172688kB
        ->  Hash Join  (cost=34358.64..869933.18 rows=3454539 width=14) (actual time=984.934..67368.804 rows=6787531 loops=1)
              Output: c.concod, cp.conparnum, cp.conpardatven
              Inner Unique: true
              Hash Cond: (cp.concod = c.concod)
              ->  Seq Scan on public.contrato_parcela cp  (cost=0.00..804229.29 rows=11941029 width=14) (actual time=0.316..57789.284 rows=11962505 loops=1)
                    Output: cp.conparseq, cp.concod, cp.conparnum, cp.conpardatcad, cp.conpardatven, cp.conparvallan, cp.conpardadadi, cp.conparbancod, cp.conparage, cp.conparcon, cp.conparnumche, cp.conpardatapre, cp.conparborent, cp.conparali, cp.conparati, cp.conparusuinc, cp.conpardatatu, cp.conparusuatu, cp.conpardatinc, cp.conparacocod, cp.enccod, cp.conparstacal, cp.tiplancod, cp.conparidt, cp.conparvalsal, cp.conparvin, cp.conparboratu, cp.conparprocod, cp.conparpro, cp.conpartax, cp.conparvalori
              ->  Hash  (cost=23428.55..23428.55 rows=874407 width=8) (actual time=983.085..983.085 rows=879841 loops=1)
                    Output: c.concod
                    Buckets: 1048576  Batches: 1  Memory Usage: 42561kB
                    ->  Index Only Scan using contrato_iu0004 on public.contrato c  (cost=0.43..23428.55 rows=874407 width=8) (actual time=0.033..610.458 rows=879841 loops=1)
                          Output: c.concod
                          Index Cond: (c.carcod = 100)
                          Heap Fetches: 140473
Planning time: 1.142 ms
Execution time: 81361.308 ms