84 lines
2.2 KiB
Go
84 lines
2.2 KiB
Go
// Copyright 2013 The ql Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSES/QL-LICENSE file.
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// 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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"github.com/juju/errors"
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"github.com/pingcap/tidb/context"
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"github.com/pingcap/tidb/expression/builtin"
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"github.com/pingcap/tidb/model"
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)
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var (
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_ Expression = (*Ident)(nil)
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)
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// Ident is the identifier expression.
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type Ident struct {
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// model.CIStr contains origin identifier name and its lowercase name.
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model.CIStr
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}
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// Clone implements the Expression Clone interface.
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func (i *Ident) Clone() Expression {
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newI := *i
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return &newI
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}
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// IsStatic implements the Expression IsStatic interface, always returns false.
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func (i *Ident) IsStatic() bool {
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return false
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}
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// String implements the Expression String interface.
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func (i *Ident) String() string {
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return i.O
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}
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// Equal checks equation with another Ident expression using lowercase identifier name.
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func (i *Ident) Equal(x *Ident) bool {
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return i.L == x.L
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}
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// Eval implements the Expression Eval interface.
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func (i *Ident) Eval(ctx context.Context, args map[interface{}]interface{}) (v interface{}, err error) {
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if _, ok := args[builtin.ExprEvalArgAggEmpty]; ok {
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// select c1, max(c1) from t where c1 = null, must get "NULL", "NULL" for empty table
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return nil, nil
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}
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if f, ok := args[ExprEvalIdentFunc]; ok {
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if got, ok := f.(func(string) (interface{}, error)); ok {
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return got(i.L)
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}
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}
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// defer func() { log.Errorf("Ident %q -> %v %v", i.S, v, err) }()
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v, ok := args[i.L]
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if !ok {
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err = errors.Errorf("unknown field %s %v", i.O, args)
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}
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return
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}
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// Accept implements Expression Accept interface.
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func (i *Ident) Accept(v Visitor) (Expression, error) {
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return v.VisitIdent(i)
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}
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