expression: improve unit test coverage of expression.go to 82.5%

expression/expression_test.go

@@ -0,0 +1,76 @@
+// Copyright 2017 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package expression
+
+import (
+	. "github.com/pingcap/check"
+	"github.com/pingcap/tidb/ast"
+	"github.com/pingcap/tidb/model"
+	"github.com/pingcap/tidb/mysql"
+	"github.com/pingcap/tidb/util/testleak"
+	"github.com/pingcap/tidb/util/types"
+)
+
+func (s *testEvaluatorSuite) TestNewCastFunc(c *C) {
+	defer testleak.AfterTest(c)()
+
+	res := NewCastFunc(types.NewFieldType(mysql.TypeJSON), &Constant{RetType: types.NewFieldType(mysql.TypeLonglong), Value: types.NewIntDatum(1)}, s.ctx)
+	c.Assert(res.FuncName.O, Equals, "cast")
+	c.Assert(res.RetType.Tp, Equals, mysql.TypeJSON)
+	_, ok := res.Function.(*builtinCastSig)
+	c.Assert(ok, IsTrue)
+}
+
+func (s *testEvaluatorSuite) TestNewValuesFunc(c *C) {
+	defer testleak.AfterTest(c)()
+
+	res := NewValuesFunc(0, types.NewFieldType(mysql.TypeLonglong), s.ctx)
+	c.Assert(res.FuncName.O, Equals, "values")
+	c.Assert(res.RetType.Tp, Equals, mysql.TypeLonglong)
+	_, ok := res.Function.(*builtinValuesSig)
+	c.Assert(ok, IsTrue)
+}
+
+func (s *testEvaluatorSuite) TestEvaluateExprWithNull(c *C) {
+	defer testleak.AfterTest(c)()
+
+	col0 := &Column{RetType: types.NewFieldType(mysql.TypeLonglong), FromID: "DataSource_0", Position: 0, ColName: model.NewCIStr("col0")}
+	col1 := &Column{RetType: types.NewFieldType(mysql.TypeLonglong), FromID: "DataSource_0", Position: 1, ColName: model.NewCIStr("col1")}
+	ifnullInner := newFunction(ast.Ifnull, col1, One)
+	ifnullOuter := newFunction(ast.Ifnull, col0, ifnullInner)
+
+	// ifnull(null, ifnull(col1, 1))
+	schema := &Schema{Columns: []*Column{col0}}
+	res, err := EvaluateExprWithNull(s.ctx, schema, ifnullOuter)
+	c.Assert(err, IsNil)
+	c.Assert(res.String(), Equals, "ifnull(<nil>, ifnull(col1, 1))")
+
+	schema.Columns = append(schema.Columns, col1)
+	// ifnull(null, ifnull(null, 1))
+	res, err = EvaluateExprWithNull(s.ctx, schema, ifnullOuter)
+	c.Assert(err, IsNil)
+	c.Assert(res.Equal(One, s.ctx), IsTrue)
+}
+
+func (s *testEvaluatorSuite) TestConstant(c *C) {
+	defer testleak.AfterTest(c)()
+
+	c.Assert(Zero.IsCorrelated(), IsFalse)
+	c.Assert(Zero.Decorrelate(nil).Equal(Zero, s.ctx), IsTrue)
+	c.Assert(Zero.HashCode(), DeepEquals, []byte{0x8, 0x0})
+	c.Assert(Zero.Equal(One, s.ctx), IsFalse)
+	res, err := Zero.MarshalJSON()
+	c.Assert(err, IsNil)
+	c.Assert(res, DeepEquals, []byte{0x22, 0x30, 0x22})
+}