在Postgres中处理列可为空时索引上的冲突

假设我有一张这样的桌子:

CREATE TABLE test (id SERIAL, first VARCHAR(10), second VARCHAR(10), other VARCHAR(10));
CREATE UNIQUE INDEX unique_index ON test (first, second);

INSERT INTO test (first, second, other)
  VALUES ('lorem', null, 'old');

INSERT INTO test (first, second, other)
  VALUES ('lorem', null, 'new')
ON CONFLICT (first, second)
  DO UPDATE SET
    other = EXCLUDED.other;

1   lorem   (null)  old
2   lorem   (null)  new