68 lines
1.7 KiB
Go
68 lines
1.7 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 expressions
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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/expression"
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)
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var (
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_ expression.Expression = (*IsNull)(nil)
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)
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// IsNull is the expression for null check.
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type IsNull struct {
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// Expr is the expression to be checked.
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Expr expression.Expression
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// Not is true, the expression is "is not null".
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Not bool
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}
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// Clone implements the Expression Clone interface.
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func (is *IsNull) Clone() (expression.Expression, error) {
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expr, err := is.Expr.Clone()
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if err != nil {
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return nil, err
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}
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return &IsNull{Expr: expr, Not: is.Not}, nil
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}
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// IsStatic implements the Expression IsStatic interface.
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func (is *IsNull) IsStatic() bool {
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return is.Expr.IsStatic()
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}
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// String implements the Expression String interface.
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func (is *IsNull) String() string {
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if is.Not {
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return fmt.Sprintf("%s IS NOT NULL", is.Expr)
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}
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return fmt.Sprintf("%s IS NULL", is.Expr)
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}
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// Eval implements the Expression Eval interface.
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func (is *IsNull) Eval(ctx context.Context, args map[interface{}]interface{}) (v interface{}, err error) {
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Val, err := is.Expr.Eval(ctx, args)
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if err != nil {
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return
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}
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return Val == nil != is.Not, nil
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}
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