/
cast.go
83 lines (74 loc) · 2.12 KB
/
cast.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
//
//
// 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 expressions
import (
"fmt"
"github.com/Dong-Chan/alloydb/context"
"github.com/Dong-Chan/alloydb/expression"
mysql "github.com/Dong-Chan/alloydb/mysqldef"
"github.com/Dong-Chan/alloydb/util/types"
)
// FunctionCast is the cast function converting value to another type, e.g, cast(expr AS signed).
// See https://dev.mysql.com/doc/refman/5.7/en/cast-functions.html#function_cast
type FunctionCast struct {
// Expr is the expression to be converted.
Expr expression.Expression
// Tp is the conversion type.
Tp *types.FieldType
}
// Clone implements the Expression Clone interface.
func (f *FunctionCast) Clone() (expression.Expression, error) {
expr, err := f.Expr.Clone()
if err != nil {
return nil, err
}
nf := &FunctionCast{
Expr: expr,
Tp: f.Tp,
}
return nf, nil
}
// IsStatic implements the Expression IsStatic interface.
func (f *FunctionCast) IsStatic() bool {
return f.Expr.IsStatic()
}
// String implements the Expression String interface.
func (f *FunctionCast) String() string {
tpStr := ""
if f.Tp.Tp == mysql.TypeLonglong {
if mysql.HasUnsignedFlag(f.Tp.Flag) {
tpStr = "UNSIGNED"
} else {
tpStr = "SIGNED"
}
} else {
tpStr = f.Tp.String()
}
return fmt.Sprintf("CAST(%s AS %s)", f.Expr.String(), tpStr)
}
// Eval implements the Expression Eval interface.
func (f *FunctionCast) Eval(ctx context.Context, args map[interface{}]interface{}) (interface{}, error) {
value, err := f.Expr.Eval(ctx, args)
if err != nil {
return nil, err
}
// Casting nil to any type returns null
if value == nil {
return nil, nil
}
nv, err := types.Convert(value, f.Tp)
if err != nil {
return nil, err
}
return nv, nil
}