73 lines
1.8 KiB
Go
73 lines
1.8 KiB
Go
// 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 (
|
|
"fmt"
|
|
|
|
"github.com/juju/errors"
|
|
"github.com/pingcap/tidb/context"
|
|
)
|
|
|
|
var (
|
|
_ Expression = (*IsNull)(nil)
|
|
)
|
|
|
|
// IsNull is the expression for null check.
|
|
type IsNull struct {
|
|
// Expr is the expression to be checked.
|
|
Expr Expression
|
|
// Not is true, the expression is "is not null".
|
|
Not bool
|
|
}
|
|
|
|
// Clone implements the Expression Clone interface.
|
|
func (is *IsNull) Clone() Expression {
|
|
expr := is.Expr.Clone()
|
|
return &IsNull{Expr: expr, Not: is.Not}
|
|
}
|
|
|
|
// IsStatic implements the Expression IsStatic interface.
|
|
func (is *IsNull) IsStatic() bool {
|
|
return is.Expr.IsStatic()
|
|
}
|
|
|
|
// String implements the Expression String interface.
|
|
func (is *IsNull) String() string {
|
|
if is.Not {
|
|
return fmt.Sprintf("%s IS NOT NULL", is.Expr)
|
|
}
|
|
|
|
return fmt.Sprintf("%s IS NULL", is.Expr)
|
|
}
|
|
|
|
// Eval implements the Expression Eval interface.
|
|
func (is *IsNull) Eval(ctx context.Context, args map[interface{}]interface{}) (v interface{}, err error) {
|
|
if err := CheckOneColumn(ctx, is.Expr); err != nil {
|
|
return nil, errors.Trace(err)
|
|
}
|
|
|
|
val, err := is.Expr.Eval(ctx, args)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
return (val == nil) != is.Not, nil
|
|
}
|
|
|
|
// Accept implements Expression Accept interface.
|
|
func (is *IsNull) Accept(v Visitor) (Expression, error) {
|
|
return v.VisitIsNull(is)
|
|
}
|