github.com/dolthub/go-mysql-server@v0.18.0/sql/expression/literal.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  	"strings"
    20  
    21  	"github.com/dolthub/vitess/go/vt/proto/query"
    22  	"github.com/shopspring/decimal"
    23  
    24  	"github.com/dolthub/go-mysql-server/sql"
    25  	"github.com/dolthub/go-mysql-server/sql/types"
    26  )
    27  
    28  // Literal represents a literal expression (string, number, bool, ...).
    29  type Literal struct {
    30  	value     interface{}
    31  	val2      sql.Value
    32  	fieldType sql.Type
    33  }
    34  
    35  var _ sql.Expression = &Literal{}
    36  var _ sql.Expression2 = &Literal{}
    37  var _ sql.CollationCoercible = &Literal{}
    38  
    39  // NewLiteral creates a new Literal expression.
    40  func NewLiteral(value interface{}, fieldType sql.Type) *Literal {
    41  	val2, _ := sql.ConvertToValue(value)
    42  	return &Literal{
    43  		value:     value,
    44  		val2:      val2,
    45  		fieldType: fieldType,
    46  	}
    47  }
    48  
    49  // Resolved implements the Expression interface.
    50  func (lit *Literal) Resolved() bool {
    51  	return true
    52  }
    53  
    54  // IsNullable implements the Expression interface.
    55  func (lit *Literal) IsNullable() bool {
    56  	return lit.value == nil
    57  }
    58  
    59  // Type implements the Expression interface.
    60  func (lit *Literal) Type() sql.Type {
    61  	return lit.fieldType
    62  }
    63  
    64  // CollationCoercibility implements the interface sql.CollationCoercible.
    65  func (lit *Literal) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
    66  	if types.IsText(lit.fieldType) {
    67  		collation, _ = lit.fieldType.CollationCoercibility(ctx)
    68  		return collation, 4
    69  	}
    70  	return sql.Collation_binary, 5
    71  }
    72  
    73  // Eval implements the Expression interface.
    74  func (lit *Literal) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
    75  	return lit.value, nil
    76  }
    77  
    78  func (lit *Literal) String() string {
    79  	switch litVal := lit.value.(type) {
    80  	case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:
    81  		return fmt.Sprintf("%d", litVal)
    82  	case string:
    83  		switch lit.fieldType.Type() {
    84  		// utf8 charset cannot encode binary string
    85  		case query.Type_VARBINARY, query.Type_BINARY:
    86  			return fmt.Sprintf("'0x%X'", litVal)
    87  		}
    88  		// Conversion of \' to \'\' required as this string will be interpreted by the sql engine.
    89  		// Backslash chars also need to be replaced.
    90  		escaped := strings.ReplaceAll(litVal, "'", "''")
    91  		escaped = strings.ReplaceAll(escaped, "\\", "\\\\")
    92  		return fmt.Sprintf("'%s'", escaped)
    93  	case decimal.Decimal:
    94  		return litVal.StringFixed(litVal.Exponent() * -1)
    95  	case []byte:
    96  		return fmt.Sprintf("0x%X", litVal)
    97  	case nil:
    98  		return "NULL"
    99  	default:
   100  		return fmt.Sprint(litVal)
   101  	}
   102  }
   103  
   104  func (lit *Literal) DebugString() string {
   105  	typeStr := lit.fieldType.String()
   106  	switch v := lit.value.(type) {
   107  	case string:
   108  		return fmt.Sprintf("%s (%s)", v, typeStr)
   109  	case []byte:
   110  		return fmt.Sprintf("BLOB(%s)", string(v))
   111  	case nil:
   112  		return fmt.Sprintf("NULL (%s)", typeStr)
   113  	case int, uint, int8, uint8, int16, uint16, int32, uint32, int64, uint64:
   114  		return fmt.Sprintf("%d (%s)", v, typeStr)
   115  	case float32, float64:
   116  		return fmt.Sprintf("%f (%s)", v, typeStr)
   117  	case bool:
   118  		return fmt.Sprintf("%t (%s)", v, typeStr)
   119  	default:
   120  		return fmt.Sprintf("%s (%s)", v, typeStr)
   121  	}
   122  }
   123  
   124  // WithChildren implements the Expression interface.
   125  func (lit *Literal) WithChildren(children ...sql.Expression) (sql.Expression, error) {
   126  	if len(children) != 0 {
   127  		return nil, sql.ErrInvalidChildrenNumber.New(lit, len(children), 0)
   128  	}
   129  	return lit, nil
   130  }
   131  
   132  // Children implements the Expression interface.
   133  func (*Literal) Children() []sql.Expression {
   134  	return nil
   135  }
   136  
   137  func (lit *Literal) Eval2(ctx *sql.Context, row sql.Row2) (sql.Value, error) {
   138  	return lit.val2, nil
   139  }
   140  
   141  func (lit *Literal) Type2() sql.Type2 {
   142  	t2, ok := lit.fieldType.(sql.Type2)
   143  	if !ok {
   144  		panic(fmt.Errorf("expected Type2, but was %T", lit.fieldType))
   145  	}
   146  	return t2
   147  }
   148  
   149  // Value returns the literal value.
   150  func (p *Literal) Value() interface{} {
   151  	return p.value
   152  }