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
|
// SPDX-FileCopyrightText: 2026 Stefan Majewsky <majewsky@gmx.net>
// SPDX-License-Identifier: Apache-2.0
package oblast
import (
"context"
"database/sql"
"fmt"
"reflect"
"sync"
"go.xyrillian.de/oblast/internal"
)
// DB wraps an [sql.DB] instance for use with Oblast's query interface.
type DB struct {
*sql.DB
dialect Dialect
plans map[reflect.Type]internal.Plan
planMutex sync.Mutex
}
func NewDB(db *sql.DB, dialect Dialect) *DB {
return &DB{
DB: db,
dialect: dialect,
plans: make(map[reflect.Type]internal.Plan),
}
}
func (d *DB) getPlan(t reflect.Type) (internal.Plan, error) {
d.planMutex.Lock()
defer d.planMutex.Unlock()
p, ok := d.plans[t]
if ok {
return p, nil
}
p, err := internal.BuildPlan(t, d.dialect)
if err == nil {
d.plans[t] = p
}
return p, err
}
// TODO: Begin() -> custom Tx type; add interface to allow Select() et all to take either *DB or *Tx
func Select[T any](ctx context.Context, db *DB, query string, args ...any) ([]T, error) {
// TODO: minimize function body to avoid binary size blowup from monomorphization
// TODO: catch error from rows.Close(), if any
// TODO: add context to errors
plan, err := db.getPlan(reflect.TypeFor[T]())
if err != nil {
return nil, err
}
rows, err := db.Query(query, args...)
if err != nil {
return nil, err
}
defer rows.Close()
columnNames, err := rows.Columns()
if err != nil {
return nil, err
}
indexes := make([][]int, len(columnNames))
for idx, columnName := range columnNames {
var ok bool
indexes[idx], ok = plan.IndexByColumnName[columnName]
if !ok {
var zero T
return nil, fmt.Errorf("result has column %q in position %d, but no field in %T has `db:%[1]q`",
columnName, idx, zero)
}
}
var result []T
slots := make([]any, len(indexes))
for rows.Next() {
var target T
rvalue := reflect.ValueOf(&target).Elem()
for idx, index := range indexes {
slots[idx] = rvalue.FieldByIndex(index).Addr().Interface()
}
err := rows.Scan(slots...)
if err != nil {
return nil, err
}
result = append(result, target)
}
return result, nil
}
|
