Weblabor

select version();
                                                   version                                                    
--------------------------------------------------------------------------------------------------------------
 PostgreSQL 9.1.10 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu/Linaro 4.8.1-10ubuntu7) 4.8.1, 64-bit
(1 row)



CREATE TABLE update_test (
  outer_ref_id SERIAL,
  author_id BIGINT NOT NULL,
  author_seq INTEGER NOT NULL,
  CONSTRAINT update_test_outer_ref_id_key UNIQUE(outer_ref_id),
  CONSTRAINT update_test_pkey PRIMARY KEY(author_id, author_seq)
);

do $$                            
declare 
author_id integer;
author_seq integer;
begin
  for author_id in 1..1000 loop
    for author_seq in 1..1000 loop
      insert into update_test (author_id, author_seq) values (author_id, author_seq);
    end loop;
  end loop;
end;
$$;
DO
Time: 20970.795 ms

commit;
COMMIT
Time: 0.729 ms

delete from update_test where author_id=888 and author_seq=500;
DELETE 1
Time: 0.903 ms

update update_test set author_seq=author_seq-1 where author_id=888 and author_seq>500;
UPDATE 500
Time: 15.749 ms

commit;
COMMIT
Time: 1.256 ms

select * from update_test where author_id=888 and author_seq in (35,250,333,420,950);
 outer_ref_id | author_id | author_seq 
--------------+-----------+------------
     20642000 |       888 |         35
     20642215 |       888 |        250
     20642298 |       888 |        333
     20642385 |       888 |        420
     20642916 |       888 |        950
(5 rows)

Time: 1.092 ms

explain analyze select * from update_test where author_id=888 and author_seq in (35,250,333,420,950);
                                                         QUERY PLAN                                                          
-----------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on update_test  (cost=36.31..1733.99 rows=2896 width=16) (actual time=0.180..0.224 rows=5 loops=1)
   Recheck Cond: ((author_id = 888) AND (author_seq = ANY ('{35,250,333,420,950}'::integer[])))
   ->  Bitmap Index Scan on update_test_pkey  (cost=0.00..35.58 rows=2896 width=0) (actual time=0.134..0.134 rows=6 loops=1)
         Index Cond: ((author_id = 888) AND (author_seq = ANY ('{35,250,333,420,950}'::integer[])))
 Total runtime: 0.287 ms
(5 rows)

Time: 2.449 ms