/
scan.go
337 lines (316 loc) · 8.91 KB
/
scan.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
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
// Copyright 2019-present Facebook Inc. All rights reserved.
// This source code is licensed under the Apache 2.0 license found
// in the LICENSE file in the root directory of this source tree.
package sql
import (
"database/sql"
"database/sql/driver"
"encoding/json"
"fmt"
"reflect"
"strings"
"time"
)
// ScanOne scans one row to the given value. It fails if the rows holds more than 1 row.
func ScanOne(rows ColumnScanner, v any) error {
columns, err := rows.Columns()
if err != nil {
return fmt.Errorf("sql/scan: failed getting column names: %w", err)
}
if n := len(columns); n != 1 {
return fmt.Errorf("sql/scan: unexpected number of columns: %d", n)
}
if !rows.Next() {
if err := rows.Err(); err != nil {
return err
}
return sql.ErrNoRows
}
if err := rows.Scan(v); err != nil {
return err
}
if rows.Next() {
return fmt.Errorf("sql/scan: expect exactly one row in result set")
}
return rows.Err()
}
// ScanInt64 scans and returns an int64 from the rows.
func ScanInt64(rows ColumnScanner) (int64, error) {
var n int64
if err := ScanOne(rows, &n); err != nil {
return 0, err
}
return n, nil
}
// ScanInt scans and returns an int from the rows.
func ScanInt(rows ColumnScanner) (int, error) {
n, err := ScanInt64(rows)
if err != nil {
return 0, err
}
return int(n), nil
}
// ScanBool scans and returns a boolean from the rows.
func ScanBool(rows ColumnScanner) (bool, error) {
var b bool
if err := ScanOne(rows, &b); err != nil {
return false, err
}
return b, nil
}
// ScanString scans and returns a string from the rows.
func ScanString(rows ColumnScanner) (string, error) {
var s string
if err := ScanOne(rows, &s); err != nil {
return "", err
}
return s, nil
}
// ScanValue scans and returns a driver.Value from the rows.
func ScanValue(rows ColumnScanner) (driver.Value, error) {
var v driver.Value
if err := ScanOne(rows, &v); err != nil {
return "", err
}
return v, nil
}
// ScanSlice scans the given ColumnScanner (basically, sql.Row or sql.Rows) into the given slice.
func ScanSlice(rows ColumnScanner, v any) error {
columns, err := rows.Columns()
if err != nil {
return fmt.Errorf("sql/scan: failed getting column names: %w", err)
}
rv := reflect.ValueOf(v)
switch {
case rv.Kind() != reflect.Ptr:
if t := reflect.TypeOf(v); t != nil {
return fmt.Errorf("sql/scan: ScanSlice(non-pointer %s)", t)
}
fallthrough
case rv.IsNil():
return fmt.Errorf("sql/scan: ScanSlice(nil)")
}
rv = reflect.Indirect(rv)
if k := rv.Kind(); k != reflect.Slice {
return fmt.Errorf("sql/scan: invalid type %s. expected slice as an argument", k)
}
scan, err := scanType(rv.Type().Elem(), columns)
if err != nil {
return err
}
if n, m := len(columns), len(scan.columns); n > m {
return fmt.Errorf("sql/scan: columns do not match (%d > %d)", n, m)
}
for rows.Next() {
values := scan.values()
if err := rows.Scan(values...); err != nil {
return fmt.Errorf("sql/scan: failed scanning rows: %w", err)
}
vv, err := scan.value(values...)
if err != nil {
return err
}
rv.Set(reflect.Append(rv, vv))
}
return rows.Err()
}
// rowScan is the configuration for scanning one sql.Row.
type rowScan struct {
// column types of a row.
columns []reflect.Type
// value functions that converts the row columns (result) to a reflect.Value.
value func(v ...any) (reflect.Value, error)
}
// values returns a []any from the configured column types.
func (r *rowScan) values() []any {
values := make([]any, len(r.columns))
for i := range r.columns {
values[i] = reflect.New(r.columns[i]).Interface()
}
return values
}
// scanType returns rowScan for the given reflect.Type.
func scanType(typ reflect.Type, columns []string) (*rowScan, error) {
switch k := typ.Kind(); {
case assignable(typ):
return &rowScan{
columns: []reflect.Type{typ},
value: func(v ...any) (reflect.Value, error) {
return reflect.Indirect(reflect.ValueOf(v[0])), nil
},
}, nil
case k == reflect.Ptr:
return scanPtr(typ, columns)
case k == reflect.Struct:
return scanStruct(typ, columns)
default:
return nil, fmt.Errorf("sql/scan: unsupported type ([]%s)", k)
}
}
var (
scannerType = reflect.TypeOf((*sql.Scanner)(nil)).Elem()
nullJSONType = reflect.TypeOf((*nullJSON)(nil)).Elem()
)
// nullJSON represents a json.RawMessage that may be NULL.
type nullJSON json.RawMessage
// Scan implements the sql.Scanner interface.
func (j *nullJSON) Scan(v interface{}) error {
if v == nil {
return nil
}
*j = v.([]byte)
return nil
}
// assignable reports if the given type can be assigned directly by `Rows.Scan`.
func assignable(typ reflect.Type) bool {
switch k := typ.Kind(); {
case typ.Implements(scannerType):
case k == reflect.Interface && typ.NumMethod() == 0:
case k == reflect.String || k >= reflect.Bool && k <= reflect.Float64:
case (k == reflect.Slice || k == reflect.Array) && typ.Elem().Kind() == reflect.Uint8:
default:
return false
}
return true
}
// scanStruct returns the configuration for scanning a sql.Row into a struct.
func scanStruct(typ reflect.Type, columns []string) (*rowScan, error) {
var (
scan = &rowScan{}
idxs = make([][]int, 0, typ.NumField())
names = make(map[string][]int, typ.NumField())
)
for i := 0; i < typ.NumField(); i++ {
f := typ.Field(i)
// Skip unexported fields.
if f.PkgPath != "" {
continue
}
// Support 1-level embedding to accept types as `type T struct {ent.T; V int}`.
if typ := f.Type; f.Anonymous && typ.Kind() == reflect.Struct {
for j := 0; j < typ.NumField(); j++ {
names[columnName(typ.Field(j))] = []int{i, j}
}
continue
}
names[columnName(f)] = []int{i}
}
for _, c := range columns {
var idx []int
// Normalize columns if necessary,
// for example: COUNT(*) => count.
switch name := strings.Split(c, "(")[0]; {
case names[name] != nil:
idx = names[name]
case names[strings.ToLower(name)] != nil:
idx = names[strings.ToLower(name)]
default:
return nil, fmt.Errorf("sql/scan: missing struct field for column: %s (%s)", c, name)
}
idxs = append(idxs, idx)
rtype := typ.Field(idx[0]).Type
if len(idx) > 1 {
rtype = rtype.Field(idx[1]).Type
}
switch {
// If the field is not support by the standard
// convertAssign, assume it is a JSON field.
case !supportsScan(rtype):
rtype = nullJSONType
// Create a pointer to the actual reflect
// types to accept optional struct fields.
case !nillable(rtype):
rtype = reflect.PtrTo(rtype)
}
scan.columns = append(scan.columns, rtype)
}
scan.value = func(vs ...any) (reflect.Value, error) {
st := reflect.New(typ).Elem()
for i, v := range vs {
rv := reflect.Indirect(reflect.ValueOf(v))
if rv.IsNil() {
continue
}
idx := idxs[i]
rvalue, ft := st.Field(idx[0]), st.Type().Field(idx[0])
if len(idx) > 1 {
// Embedded field.
rvalue, ft = rvalue.Field(idx[1]), ft.Type.Field(idx[1])
}
switch {
case rv.Type() == nullJSONType:
if rv = reflect.Indirect(rv); rv.IsNil() {
continue
}
if err := json.Unmarshal(rv.Bytes(), rvalue.Addr().Interface()); err != nil {
return reflect.Value{}, fmt.Errorf("unmarshal field %q: %w", ft.Name, err)
}
case !nillable(rvalue.Type()):
rv = reflect.Indirect(rv)
fallthrough
default:
rvalue.Set(rv)
}
}
return st, nil
}
return scan, nil
}
// columnName returns the column name of a struct-field.
func columnName(f reflect.StructField) string {
name := strings.ToLower(f.Name)
if tag, ok := f.Tag.Lookup("sql"); ok {
name = tag
} else if tag, ok := f.Tag.Lookup("json"); ok {
name = strings.Split(tag, ",")[0]
}
return name
}
// nillable reports if the reflect-type can have nil value.
func nillable(t reflect.Type) bool {
switch t.Kind() {
case reflect.Interface, reflect.Slice, reflect.Map, reflect.Ptr, reflect.UnsafePointer:
return true
}
return false
}
// scanPtr wraps the underlying type with rowScan.
func scanPtr(typ reflect.Type, columns []string) (*rowScan, error) {
typ = typ.Elem()
scan, err := scanType(typ, columns)
if err != nil {
return nil, err
}
wrap := scan.value
scan.value = func(vs ...any) (reflect.Value, error) {
v, err := wrap(vs...)
if err != nil {
return reflect.Value{}, err
}
pt := reflect.PtrTo(v.Type())
pv := reflect.New(pt.Elem())
pv.Elem().Set(v)
return pv, nil
}
return scan, nil
}
func supportsScan(t reflect.Type) bool {
if t.Implements(scannerType) || reflect.PtrTo(t).Implements(scannerType) {
return true
}
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
switch t.Kind() {
case reflect.Bool, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
reflect.Float32, reflect.Float64, reflect.Pointer, reflect.String:
return true
case reflect.Slice:
return t == reflect.TypeOf(sql.RawBytes(nil)) || t == reflect.TypeOf([]byte(nil))
case reflect.Interface:
return t == reflect.TypeOf((*any)(nil)).Elem()
default:
return t == reflect.TypeOf(time.Time{}) || t.Implements(scannerType)
}
}