92 lines
2.4 KiB
Go
92 lines
2.4 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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"strings"
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"github.com/juju/errors"
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"github.com/ngaut/log"
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"github.com/pingcap/tidb/context"
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"golang.org/x/text/transform"
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)
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// FunctionConvert provides a way to convert data between different character sets.
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// See: https://dev.mysql.com/doc/refman/5.7/en/cast-functions.html#function_convert
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type FunctionConvert struct {
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Expr Expression
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Charset string
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}
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// Clone implements the Expression Clone interface.
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func (f *FunctionConvert) Clone() Expression {
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expr := f.Expr.Clone()
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nf := &FunctionConvert{
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Expr: expr,
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Charset: f.Charset,
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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 *FunctionConvert) 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 *FunctionConvert) String() string {
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return fmt.Sprintf("CONVERT(%s AS %s)", f.Expr.String(), f.Charset)
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}
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// Eval implements the Expression Eval interface.
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func (f *FunctionConvert) 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 nil
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if value == nil {
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return nil, nil
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}
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str, ok := value.(string)
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if !ok {
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return nil, nil
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}
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if strings.ToLower(f.Charset) == "ascii" {
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return value, nil
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} else if strings.ToLower(f.Charset) == "utf8mb4" {
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return value, nil
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}
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encoding, _ := Lookup(f.Charset)
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if encoding == nil {
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return nil, fmt.Errorf("unknown encoding: %s", f.Charset)
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}
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target, _, err := transform.String(encoding.NewDecoder(), str)
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if err != nil {
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log.Errorf("Convert %s to %s with error: %v", str, f.Charset, err)
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return nil, errors.Trace(err)
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}
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return target, nil
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}
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// Accept implements Expression Accept interface.
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func (f *FunctionConvert) Accept(v Visitor) (Expression, error) {
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return v.VisitFunctionConvert(f)
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}
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