[expression] coalesce shoudl cast return values (#2853)

Author: max-hoffman

enginetest/queries/queries.go

@@ -842,6 +842,26 @@ var QueryTests = []QueryTest{
 		Query:    "SELECT 1 WHERE ((1 IN (NULL * 1)) IS NULL);",
 		Expected: []sql.Row{{1}},
 	},
+	{
+		Query:    "select coalesce(1, 0.0);",
+		Expected: []sql.Row{{"1"}},
+	},
+	{
+		Query:    "select coalesce(1, '0');",
+		Expected: []sql.Row{{"1"}},
+	},
+	{
+		Query:    "select coalesce(1, 'x');",
+		Expected: []sql.Row{{"1"}},
+	},
+	{
+		Query:    "select coalesce(1, 1);",
+		Expected: []sql.Row{{1}},
+	},
+	{
+		Query:    "select coalesce(1, CAST('2017-08-29' AS DATE))",
+		Expected: []sql.Row{{"1"}},
+	},
 	{
 		Query:    "SELECT count(*) from mytable WHERE ((i IN (NULL >= 1)) IS NULL);",
 		Expected: []sql.Row{{3}},

sql/expression/function/coalesce.go

@@ -27,6 +27,7 @@ import (
 // Coalesce returns the first non-NULL value in the list, or NULL if there are no non-NULL values.
 type Coalesce struct {
 	args []sql.Expression
+	typ  sql.Type
 }
 
 var _ sql.FunctionExpression = (*Coalesce)(nil)
@@ -38,7 +39,7 @@ func NewCoalesce(args ...sql.Expression) (sql.Expression, error) {
 		return nil, sql.ErrInvalidArgumentNumber.New("COALESCE", "1 or more", 0)
 	}
 
-	return &Coalesce{args}, nil
+	return &Coalesce{args: args}, nil
 }
 
 // FunctionName implements sql.FunctionExpression
@@ -54,6 +55,9 @@ func (c *Coalesce) Description() string {
 // Type implements the sql.Expression interface.
 // The return type of Type() is the aggregated type of the argument types.
 func (c *Coalesce) Type() sql.Type {
+	if c.typ != nil {
+		return c.typ
+	}
 	retType := types.Null
 	for i, arg := range c.args {
 		if arg == nil {
@@ -120,6 +124,7 @@ func (c *Coalesce) Type() sql.Type {
 		}
 	}
 
+	c.typ = retType
 	return retType
 }
 
@@ -201,6 +206,12 @@ func (c *Coalesce) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
 			continue
 		}
 
+		if !types.IsEnum(c.Type()) && !types.IsSet(c.Type()) {
+			val, _, err = c.Type().Convert(val)
+			if err != nil {
+				return nil, err
+			}
+		}
 		return val, nil
 	}
 

sql/expression/function/coalesce_test.go

@@ -45,7 +45,7 @@ func TestCoalesce(t *testing.T) {
 				expression.NewLiteral(2, types.Int32),
 				expression.NewLiteral(3, types.Int32),
 			},
-			expected: 1,
+			expected: int32(1),
 			typ:      types.Int32,
 			nullable: false,
 		},
@@ -56,7 +56,7 @@ func TestCoalesce(t *testing.T) {
 				nil,
 				expression.NewLiteral(3, types.Int32),
 			},
-			expected: 3,
+			expected: int32(3),
 			typ:      types.Int32,
 			nullable: false,
 		},
@@ -100,7 +100,7 @@ func TestCoalesce(t *testing.T) {
 				expression.NewLiteral(decimal.NewFromFloat(2.0), types.MustCreateDecimalType(10, 0)),
 				expression.NewLiteral("3", types.LongText),
 			},
-			expected: 1,
+			expected: "1",
 			typ:      types.LongText,
 			nullable: false,
 		},
@@ -110,7 +110,7 @@ func TestCoalesce(t *testing.T) {
 				expression.NewLiteral(1, types.Int32),
 				expression.NewLiteral(2, types.Uint32),
 			},
-			expected: 1,
+			expected: decimal.New(1, 0),
 			typ:      types.MustCreateDecimalType(20, 0),
 			nullable: false,
 		},
@@ -120,7 +120,7 @@ func TestCoalesce(t *testing.T) {
 				expression.NewLiteral(1, types.Int32),
 				expression.NewLiteral(2, types.Uint32),
 			},
-			expected: 1,
+			expected: decimal.New(1, 0),
 			typ:      types.MustCreateDecimalType(20, 0),
 			nullable: false,
 		},
@@ -130,7 +130,7 @@ func TestCoalesce(t *testing.T) {
 				expression.NewLiteral(1, types.MustCreateDecimalType(10, 0)),
 				expression.NewLiteral(2, types.Float64),
 			},
-			expected: 1,
+			expected: float64(1),
 			typ:      types.Float64,
 			nullable: false,
 		},
@@ -139,7 +139,7 @@ func TestCoalesce(t *testing.T) {
 			input: []sql.Expression{
 				expression.NewLiteral(2, types.Float64),
 			},
-			expected: 2,
+			expected: float64(2),
 			typ:      types.Float64,
 			nullable: false,
 		},
@@ -148,7 +148,7 @@ func TestCoalesce(t *testing.T) {
 			input: []sql.Expression{
 				expression.NewLiteral(1, types.Float64),
 			},
-			expected: 1,
+			expected: float64(1),
 			typ:      types.Float64,
 			nullable: false,
 		},
@@ -158,7 +158,7 @@ func TestCoalesce(t *testing.T) {
 				expression.NewLiteral(1, types.NewSystemIntType("int1", 0, 10, false)),
 				expression.NewLiteral(2, types.NewSystemIntType("int2", 0, 10, false)),
 			},
-			expected: 1,
+			expected: int64(1),
 			typ:      types.Int64,
 			nullable: false,
 		},
@@ -168,7 +168,7 @@ func TestCoalesce(t *testing.T) {
 				expression.NewLiteral(1, types.NewSystemIntType("int1", 0, 10, false)),
 				expression.NewLiteral(2, types.NewSystemUintType("int2", 0, 10)),
 			},
-			expected: 1,
+			expected: decimal.New(1, 0),
 			typ:      types.MustCreateDecimalType(20, 0),
 			nullable: false,
 		},
@@ -178,7 +178,7 @@ func TestCoalesce(t *testing.T) {
 				expression.NewLiteral(1, types.NewSystemUintType("int1", 0, 10)),
 				expression.NewLiteral(2, types.NewSystemUintType("int2", 0, 10)),
 			},
-			expected: 1,
+			expected: uint64(1),
 			typ:      types.Uint64,
 			nullable: false,
 		},
@@ -188,7 +188,7 @@ func TestCoalesce(t *testing.T) {
 				expression.NewLiteral(1.0, types.NewSystemDoubleType("dbl1", 0.0, 10.0)),
 				expression.NewLiteral(2.0, types.NewSystemDoubleType("dbl2", 0.0, 10.0)),
 			},
-			expected: 1.0,
+			expected: float64(1),
 			typ:      types.Float64,
 			nullable: false,
 		},
@@ -249,19 +249,19 @@ func TestComposeCoalasce(t *testing.T) {
 	require.Equal(t, types.Int32, c2.Type())
 	v, err = c2.Eval(ctx, nil)
 	require.NoError(t, err)
-	require.Equal(t, 1, v)
+	require.Equal(t, int32(1), v)
 
 	c3, err := NewCoalesce(nil, c1, c2)
 	require.NoError(t, err)
 	require.Equal(t, types.Int32, c3.Type())
 	v, err = c3.Eval(ctx, nil)
 	require.NoError(t, err)
-	require.Equal(t, 1, v)
+	require.Equal(t, int32(1), v)
 
 	c4, err := NewCoalesce(expression.NewLiteral(nil, types.Null), c1, c2)
 	require.NoError(t, err)
 	require.Equal(t, types.Int32, c4.Type())
 	v, err = c4.Eval(ctx, nil)
 	require.NoError(t, err)
-	require.Equal(t, 1, v)
+	require.Equal(t, int32(1), v)
 }