UPDATE test SET x = x + 1 WHERE x >= 1000;
SELECT ctid, * FROM test WHERE x > 1000;
UPDATE test SET x = x + 1 WHERE x >= 1000;
SELECT ctid, * FROM test WHERE x > 1000;
UPDATE test SET x = x + 1 WHERE x >= 1000;
SELECT ctid, * FROM test WHERE x > 1000;
UPDATE test SET x = x + 1 WHERE x >= 1000;
SELECT ctid, * FROM test WHERE x > 1000;

CREATE INDEX i_test ON test(x);