query performance – Postgresql update slow on a relative small/medium table

I’m trying to run an update on a table with 10 million rows (I just need to update a few), but the query is taking more time than I would like.

This is the table deinifition:

CREATE TABLE det_price_list
      price_list_id     BIGINT NOT NULL
        CONSTRAINT fk_det_list_precio_venta_2
        REFERENCES price_list

      det_price_list_id BIGINT NOT NULL,
      product_id        VARCHAR(25),
      account_id        BIGINT,
      price             NUMERIC(22, 8),
      currency_id       BIGINT,
      last_updated      TIMESTAMP,
      CONSTRAINT pk_det_price_list
      PRIMARY KEY (price_list_id, det_price_list_id),
      CONSTRAINT fk_det_list_precio_venta_1
      FOREIGN KEY (product_id, account_id) REFERENCES product
      CONSTRAINT fk_det_price_list_4
      FOREIGN KEY (currency_id, account_id) REFERENCES currency

With this index:

CREATE UNIQUE INDEX indice_det_lista_item
  ON det_price_list (product_id, price_list_id);

CREATE INDEX ix_det_price_list_5
  ON det_price_list (price_list_id, account_id, product_id);

CREATE INDEX ix_det_price_list_1
  ON det_price_list (price_list_id);

CREATE INDEX ix_det_price_list_2
  ON det_price_list (product_id);

CREATE INDEX ix_det_price_list_6
  ON det_price_list (account_id, product_id, price_list_id, last_updated);

CREATE INDEX ix_det_price_list_3
  ON det_price_list (account_id);

CREATE INDEX ix_det_price_list_4
  ON det_price_list (last_updated);

CREATE INDEX det_price_list_account_id_price_list_id_currency_id_i
  ON det_price_list (account_id, price_list_id, currency_id);

And this is the query:

update det_price_list d
    set last_updated = current_timestamp
  where d.account_id = 994
  AND   price_list_id = 4338
  and d.currency_id= 2;

Also here is the query plan using EXPLAIN (ANALYZE, BUFFERS):

Update on det_price_list d  (cost=0.56..219.89 rows=60 width=77) (actual time=1806.823..1806.823 rows=0 loops=1)
  Buffers: shared hit=1040857 read=1704 dirtied=8839
  I/O Timings: read=1.814
  ->  Index Scan using det_price_list_account_id_price_list_id_currency_id_i  on det_price_list d  (cost=0.56..219.89 rows=60 width=77) (actual time=0.034..28.386 rows=26776 loops=1)
        Index Cond: ((account_id  = 994) AND (price_list_id  = 4338) AND (currency_id = 2))
        Buffers: shared hit=2740 dirtied=621
Planning time: 0.157 ms
Execution time: 1806.873 ms

The query is using the index. I’ve already tried to vacumm, vacumm full, reindex and analyze but i can’t reduce that time. I can’t copy into another table and drop the old one because it is not a complete update and also the table is used constantly.