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

     1  // Copyright 2022 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 types
    16  
    17  import (
    18  	"reflect"
    19  
    20  	"github.com/dolthub/vitess/go/sqltypes"
    21  	"github.com/dolthub/vitess/go/vt/proto/query"
    22  	"gopkg.in/src-d/go-errors.v1"
    23  
    24  	"github.com/dolthub/go-mysql-server/sql"
    25  )
    26  
    27  var (
    28  	Null sql.NullType = nullType{}
    29  
    30  	// ErrValueNotNil is thrown when a value that was expected to be nil, is not
    31  	ErrValueNotNil = errors.NewKind("value not nil: %#v")
    32  )
    33  
    34  type nullType struct{}
    35  
    36  // Compare implements Type interface. Note that while this returns 0 (equals)
    37  // for ordering purposes, in SQL NULL != NULL.
    38  func (t nullType) Compare(a interface{}, b interface{}) (int, error) {
    39  	return 0, nil
    40  }
    41  
    42  // Convert implements Type interface.
    43  func (t nullType) Convert(v interface{}) (interface{}, sql.ConvertInRange, error) {
    44  	if v != nil {
    45  		return nil, sql.InRange, ErrValueNotNil.New(v)
    46  	}
    47  
    48  	return nil, sql.InRange, nil
    49  }
    50  
    51  // MaxTextResponseByteLength implements the Type interface
    52  func (t nullType) MaxTextResponseByteLength(_ *sql.Context) uint32 {
    53  	return 0
    54  }
    55  
    56  // MustConvert implements the Type interface.
    57  func (t nullType) MustConvert(v interface{}) interface{} {
    58  	value, _, err := t.Convert(v)
    59  	if err != nil {
    60  		panic(err)
    61  	}
    62  	return value
    63  }
    64  
    65  // Equals implements the Type interface.
    66  func (t nullType) Equals(otherType sql.Type) bool {
    67  	_, ok := otherType.(nullType)
    68  	return ok
    69  }
    70  
    71  // Promote implements the Type interface.
    72  func (t nullType) Promote() sql.Type {
    73  	return t
    74  }
    75  
    76  // SQL implements Type interface.
    77  func (t nullType) SQL(*sql.Context, []byte, interface{}) (sqltypes.Value, error) {
    78  	return sqltypes.NULL, nil
    79  }
    80  
    81  // String implements Type interface.
    82  func (t nullType) String() string {
    83  	return "null"
    84  }
    85  
    86  // Type implements Type interface.
    87  func (t nullType) Type() query.Type {
    88  	return sqltypes.Null
    89  }
    90  
    91  // ValueType implements Type interface.
    92  func (t nullType) ValueType() reflect.Type {
    93  	return nil
    94  }
    95  
    96  // Zero implements Type interface.
    97  func (t nullType) Zero() interface{} {
    98  	return nil
    99  }
   100  
   101  // CollationCoercibility implements sql.CollationCoercible interface.
   102  func (nullType) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
   103  	return sql.Collation_binary, 6
   104  }