102 lines
2.7 KiB
Go
102 lines
2.7 KiB
Go
// Copyright 2015 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package expression
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import (
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"fmt"
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"github.com/pingcap/tidb/context"
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"github.com/pingcap/tidb/mysql"
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"github.com/pingcap/tidb/util/types"
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)
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// castOperatopr is the operator type for cast function.
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type castFunctionType int
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const (
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// CastFunction is CAST function.
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CastFunction castFunctionType = iota + 1
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// ConvertFunction is CONVERT function.
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ConvertFunction
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// BinaryOperator is BINARY operator.
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BinaryOperator
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)
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// FunctionCast is the cast function converting value to another type, e.g, cast(expr AS signed).
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// See https://dev.mysql.com/doc/refman/5.7/en/cast-functions.html
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type FunctionCast struct {
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// Expr is the expression to be converted.
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Expr Expression
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// Tp is the conversion type.
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Tp *types.FieldType
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// Cast, Convert and Binary share this struct.
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FunctionType castFunctionType
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}
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// Clone implements the Expression Clone interface.
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func (f *FunctionCast) Clone() Expression {
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expr := f.Expr.Clone()
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nf := &FunctionCast{
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Expr: expr,
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Tp: f.Tp,
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FunctionType: f.FunctionType,
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}
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return nf
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}
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// IsStatic implements the Expression IsStatic interface.
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func (f *FunctionCast) IsStatic() bool {
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return f.Expr.IsStatic()
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}
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// String implements the Expression String interface.
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func (f *FunctionCast) String() string {
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tpStr := ""
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if f.Tp.Tp == mysql.TypeLonglong {
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if mysql.HasUnsignedFlag(f.Tp.Flag) {
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tpStr = "UNSIGNED"
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} else {
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tpStr = "SIGNED"
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}
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} else {
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tpStr = f.Tp.String()
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}
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if f.FunctionType == ConvertFunction {
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return fmt.Sprintf("CONVERT(%s, %s)", f.Expr.String(), tpStr)
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} else if f.FunctionType == BinaryOperator {
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return fmt.Sprintf("BINARY %s", f.Expr.String())
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}
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return fmt.Sprintf("CAST(%s AS %s)", f.Expr.String(), tpStr)
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}
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// Eval implements the Expression Eval interface.
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func (f *FunctionCast) Eval(ctx context.Context, args map[interface{}]interface{}) (interface{}, error) {
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value, err := f.Expr.Eval(ctx, args)
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if err != nil {
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return nil, err
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}
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// Casting nil to any type returns null
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if value == nil {
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return nil, nil
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}
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return types.Cast(value, f.Tp), nil
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}
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// Accept implements Expression Accept interface.
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func (f *FunctionCast) Accept(v Visitor) (Expression, error) {
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return v.VisitFunctionCast(f)
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}
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