105 lines
2.9 KiB
Go
105 lines
2.9 KiB
Go
// Copyright 2013 The ql Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSES/QL-LICENSE file.
|
|
|
|
// 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 expression
|
|
|
|
import (
|
|
"github.com/juju/errors"
|
|
"github.com/pingcap/tidb/context"
|
|
"github.com/pingcap/tidb/expression/builtin"
|
|
|
|
"github.com/pingcap/tidb/model"
|
|
)
|
|
|
|
var (
|
|
_ Expression = (*Ident)(nil)
|
|
)
|
|
|
|
const (
|
|
// IdentReferSelectList means the identifier reference is in select list.
|
|
IdentReferSelectList = 1
|
|
// IdentReferFromTable means the identifier reference is in FROM table.
|
|
IdentReferFromTable = 2
|
|
)
|
|
|
|
// Ident is the identifier expression.
|
|
type Ident struct {
|
|
// model.CIStr contains origin identifier name and its lowercase name.
|
|
model.CIStr
|
|
|
|
// ReferScope means where the identifer reference is, select list or from.
|
|
ReferScope int
|
|
|
|
// ReferIndex is the index to get the identifer data.
|
|
ReferIndex int
|
|
}
|
|
|
|
// Clone implements the Expression Clone interface.
|
|
func (i *Ident) Clone() Expression {
|
|
newI := *i
|
|
return &newI
|
|
}
|
|
|
|
// IsStatic implements the Expression IsStatic interface, always returns false.
|
|
func (i *Ident) IsStatic() bool {
|
|
return false
|
|
}
|
|
|
|
// String implements the Expression String interface.
|
|
func (i *Ident) String() string {
|
|
return i.O
|
|
}
|
|
|
|
// Equal checks equation with another Ident expression using lowercase identifier name.
|
|
func (i *Ident) Equal(x *Ident) bool {
|
|
return i.L == x.L
|
|
}
|
|
|
|
// Eval implements the Expression Eval interface.
|
|
func (i *Ident) Eval(ctx context.Context, args map[interface{}]interface{}) (v interface{}, err error) {
|
|
if _, ok := args[builtin.ExprEvalArgAggEmpty]; ok {
|
|
// select c1, max(c1) from t where c1 = null, must get "NULL", "NULL" for empty table
|
|
return nil, nil
|
|
}
|
|
|
|
// TODO: we will unify ExprEvalIdentReferFunc and ExprEvalIdentFunc later,
|
|
// now just put them here for refactor step by step.
|
|
if f, ok := args[ExprEvalIdentReferFunc]; ok {
|
|
if got, ok := f.(func(string, int, int) (interface{}, error)); ok {
|
|
return got(i.L, i.ReferScope, i.ReferIndex)
|
|
}
|
|
}
|
|
|
|
if f, ok := args[ExprEvalIdentFunc]; ok {
|
|
if got, ok := f.(func(string) (interface{}, error)); ok {
|
|
return got(i.L)
|
|
}
|
|
}
|
|
|
|
// defer func() { log.Errorf("Ident %q -> %v %v", i.S, v, err) }()
|
|
v, ok := args[i.L]
|
|
if !ok {
|
|
err = errors.Errorf("unknown field %s %v", i.O, args)
|
|
}
|
|
return
|
|
}
|
|
|
|
// Accept implements Expression Accept interface.
|
|
func (i *Ident) Accept(v Visitor) (Expression, error) {
|
|
return v.VisitIdent(i)
|
|
}
|