@Test
  public final void testComparatorsFromJoinQual() {
    Schema outerSchema = new Schema();
    outerSchema.addColumn("employee.id1", CatalogUtil.newSimpleDataType(Type.INT4));
    outerSchema.addColumn("employee.id2", CatalogUtil.newSimpleDataType(Type.INT4));
    Schema innerSchema = new Schema();
    innerSchema.addColumn("people.fid1", CatalogUtil.newSimpleDataType(Type.INT4));
    innerSchema.addColumn("people.fid2", CatalogUtil.newSimpleDataType(Type.INT4));

    FieldEval f1 = new FieldEval("employee.id1", CatalogUtil.newSimpleDataType(Type.INT4));
    FieldEval f2 = new FieldEval("people.fid1", CatalogUtil.newSimpleDataType(Type.INT4));
    FieldEval f3 = new FieldEval("employee.id2", CatalogUtil.newSimpleDataType(Type.INT4));
    FieldEval f4 = new FieldEval("people.fid2", CatalogUtil.newSimpleDataType(Type.INT4));

    EvalNode joinQual = new BinaryEval(EvalType.EQUAL, f1, f2);
    TupleComparator[] comparators =
        PlannerUtil.getComparatorsFromJoinQual(joinQual, outerSchema, innerSchema);

    Tuple t1 = new VTuple(2);
    t1.put(0, DatumFactory.createInt4(1));
    t1.put(1, DatumFactory.createInt4(2));

    Tuple t2 = new VTuple(2);
    t2.put(0, DatumFactory.createInt4(2));
    t2.put(1, DatumFactory.createInt4(3));

    TupleComparator outerComparator = comparators[0];
    assertTrue(outerComparator.compare(t1, t2) < 0);
    assertTrue(outerComparator.compare(t2, t1) > 0);

    TupleComparator innerComparator = comparators[1];
    assertTrue(innerComparator.compare(t1, t2) < 0);
    assertTrue(innerComparator.compare(t2, t1) > 0);

    // tests for composited join key
    EvalNode joinQual2 = new BinaryEval(EvalType.EQUAL, f3, f4);
    EvalNode compositedJoinQual = new BinaryEval(EvalType.AND, joinQual, joinQual2);
    comparators =
        PlannerUtil.getComparatorsFromJoinQual(compositedJoinQual, outerSchema, innerSchema);

    outerComparator = comparators[0];
    assertTrue(outerComparator.compare(t1, t2) < 0);
    assertTrue(outerComparator.compare(t2, t1) > 0);

    innerComparator = comparators[1];
    assertTrue(innerComparator.compare(t1, t2) < 0);
    assertTrue(innerComparator.compare(t2, t1) > 0);
  }