github.com/dolthub/go-mysql-server@v0.18.0/sql/expression/boolean.go (about)

     1  // Copyright 2020-2021 Dolthub, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package expression
    16  
    17  import (
    18  	"fmt"
    19  
    20  	"github.com/dolthub/go-mysql-server/sql"
    21  	"github.com/dolthub/go-mysql-server/sql/types"
    22  )
    23  
    24  // Not is a node that negates an expression.
    25  type Not struct {
    26  	UnaryExpression
    27  }
    28  
    29  var _ sql.Expression = (*Not)(nil)
    30  var _ sql.CollationCoercible = (*Not)(nil)
    31  
    32  // NewNot returns a new Not node.
    33  func NewNot(child sql.Expression) *Not {
    34  	return &Not{UnaryExpression{child}}
    35  }
    36  
    37  // Type implements the Expression interface.
    38  func (e *Not) Type() sql.Type {
    39  	return types.Boolean
    40  }
    41  
    42  // CollationCoercibility implements the interface sql.CollationCoercible.
    43  func (*Not) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
    44  	return sql.Collation_binary, 5
    45  }
    46  
    47  // Eval implements the Expression interface.
    48  func (e *Not) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
    49  	v, err := e.Child.Eval(ctx, row)
    50  	if err != nil {
    51  		return nil, err
    52  	}
    53  	if v == nil {
    54  		return nil, nil
    55  	}
    56  
    57  	b, ok := v.(bool)
    58  	if !ok {
    59  		b, err = sql.ConvertToBool(ctx, v)
    60  		if err != nil {
    61  			return nil, err
    62  		}
    63  	}
    64  
    65  	return !b, nil
    66  }
    67  
    68  func (e *Not) String() string {
    69  	return fmt.Sprintf("(NOT(%s))", e.Child)
    70  }
    71  
    72  func (e *Not) DebugString() string {
    73  	pr := sql.NewTreePrinter()
    74  	_ = pr.WriteNode("NOT")
    75  	children := []string{sql.DebugString(e.Child)}
    76  	_ = pr.WriteChildren(children...)
    77  	return pr.String()
    78  }
    79  
    80  // WithChildren implements the Expression interface.
    81  func (e *Not) WithChildren(children ...sql.Expression) (sql.Expression, error) {
    82  	if len(children) != 1 {
    83  		return nil, sql.ErrInvalidChildrenNumber.New(e, len(children), 1)
    84  	}
    85  	return NewNot(children[0]), nil
    86  }