*: Remove conversion function

It is useless in MySQL and will cause conflict with
year/time/datetime/date function.

expression/expressions/conversion.go

@@ -1,64 +0,0 @@
-// Copyright 2015 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 expressions
-
-import (
-	"fmt"
-
-	"github.com/pingcap/tidb/context"
-	"github.com/pingcap/tidb/expression"
-	"github.com/pingcap/tidb/util/types"
-)
-
-var (
-	_ expression.Expression = (*Conversion)(nil)
-)
-
-// Conversion is the conversion expression like "type ()".
-type Conversion struct {
-	// Tp is the conversion type.
-	Tp byte
-	// Val is the expression to be converted.
-	Val expression.Expression
-}
-
-// Clone implements the Expression Clone interface.
-func (c *Conversion) Clone() (expression.Expression, error) {
-	Val, err := c.Val.Clone()
-	if err != nil {
-		return nil, err
-	}
-
-	return &Conversion{Tp: c.Tp, Val: Val}, nil
-}
-
-// IsStatic implements the Expression IsStatic interface.
-func (c *Conversion) IsStatic() bool {
-	return c.Val.IsStatic()
-}
-
-// String implements the Expression String interface.
-func (c *Conversion) String() string {
-	return fmt.Sprintf("%s(%s)", types.TypeStr(c.Tp), c.Val)
-}
-
-// Eval implements the Expression Eval interface.
-func (c *Conversion) Eval(ctx context.Context, args map[interface{}]interface{}) (v interface{}, err error) {
-	Val, err := c.Val.Eval(ctx, args)
-	if err != nil {
-		return
-	}
-	ft := types.NewFieldType(c.Tp)
-	return types.Convert(Val, ft)
-}

expression/expressions/conversion_test.go

@@ -1,37 +0,0 @@
-package expressions
-
-import (
-	"errors"
-
-	. "github.com/pingcap/check"
-	mysql "github.com/pingcap/tidb/mysqldef"
-)
-
-var _ = Suite(&testConversionSuite{})
-
-type testConversionSuite struct {
-}
-
-func (s *testConversionSuite) TestConversion(c *C) {
-	expr := Conversion{
-		Tp:  mysql.TypeLonglong,
-		Val: Value{int64(1)},
-	}
-
-	v, err := expr.Eval(nil, nil)
-	c.Assert(err, IsNil)
-	c.Assert(v, Equals, int64(1))
-	c.Assert(expr.IsStatic(), IsTrue)
-	c.Assert(len(expr.String()), Greater, 0)
-
-	_, err = expr.Clone()
-	c.Assert(err, IsNil)
-
-	// test error
-	expr.Val = mockExpr{err: errors.New("must error")}
-	_, err = expr.Clone()
-	c.Assert(err, NotNil)
-
-	_, err = expr.Eval(nil, nil)
-	c.Assert(err, NotNil)
-}

expression/expressions/helper.go

@@ -163,8 +163,6 @@ func mentionedAggregateFuncs(e expression.Expression, m *[]expression.Expression
 		for _, e := range x.Args {
 			mentionedAggregateFuncs(e, m)
 		}
-	case *Conversion:
-		mentionedAggregateFuncs(x.Val, m)
 	case *IsNull:
 		mentionedAggregateFuncs(x.Expr, m)
 	case *PExpr:
@@ -243,8 +241,6 @@ func mentionedColumns(e expression.Expression, m map[string]bool, names *[]strin
 		for _, e := range x.Args {
 			mentionedColumns(e, m, names)
 		}
-	case *Conversion:
-		mentionedColumns(x.Val, m, names)
 	case *Ident:
 		name := x.L
 		if !m[name] {

expression/expressions/helper_test.go

@@ -27,7 +27,6 @@ func (s *testHelperSuite) TestContainAggFunc(c *C) {
 		{&BinaryOperation{L: v, R: v}, false},
 		{&Call{F: "count", Args: []expression.Expression{v}}, true},
 		{&Call{F: "abs", Args: []expression.Expression{v}}, false},
-		{&Conversion{Val: v}, false},
 		{&IsNull{Expr: v}, false},
 		{&PExpr{Expr: v}, false},
 		{&PatternIn{Expr: v, List: []expression.Expression{v}}, false},
@@ -59,7 +58,6 @@ func (s *testHelperSuite) TestMentionedColumns(c *C) {
 		{&BinaryOperation{L: v, R: v}, 0},
 		{&Ident{model.NewCIStr("id")}, 1},
 		{&Call{F: "count", Args: []expression.Expression{v}}, 0},
-		{&Conversion{Val: v}, 0},
 		{&IsNull{Expr: v}, 0},
 		{&PExpr{Expr: v}, 0},
 		{&PatternIn{Expr: v, List: []expression.Expression{v}}, 0},

parser/parser.y

@@ -270,7 +270,6 @@ import (
 	ConstraintKeywordOpt	"Constraint Keyword or empty"
 	ConstraintOpt		"optional column value constraint"
 	ConstraintOpts		"optional column value constraints"
-	Conversion		"conversion"
 	CreateDatabase		"Create {DATABASE | SCHEMA}"
 	CreateDatabaseStmt	"Create Database Statement"
 	CreateIndexStmt		"CREATE INDEX statement"
@@ -855,14 +854,6 @@ ConstraintOpts:
 		}
 	}
 
-
-Conversion:
-	Type '(' Expression ')'
-	{
-		t := $1.(*types.FieldType)
-		$$ = &expressions.Conversion{Tp: t.Tp, Val: expressions.Expr($3)}
-	}
-
 CreateIndexStmt:
 	"CREATE" CreateIndexStmtUnique "INDEX" Identifier "ON" TableIdent '(' IndexColNameList ')'
 	{
@@ -1738,7 +1729,6 @@ OrderByOptional:
 	
 PrimaryExpression:
 	Operand
-|	Conversion
 |	Function
 |	SubSelect
 |	'!' PrimaryExpression %prec neg