CREATE TABLE t1(x);
  CREATE TABLE t2(y);
  CREATE TABLE t3(z);

  CREATE INDEX i1 ON t1(x);
  CREATE INDEX i2 ON t2(y);

  INSERT INTO t1 VALUES(1);
  INSERT INTO t2 VALUES(1);
  ANALYZE;

  SELECT * FROM t1 WHERE x=1;
  SELECT * FROM t2 WHERE y=1;