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// SPDX-FileCopyrightText: 2026 Stefan Majewsky <majewsky@gmx.net>
// SPDX-License-Identifier: Apache-2.0
package oblast
import (
"context"
"database/sql"
"fmt"
"reflect"
"sync"
)
// DB wraps an [sql.DB] instance for use with Oblast's query interface.
type DB struct {
*sql.DB
dialect Dialect
plans map[reflect.Type]plan
planMutex sync.Mutex
}
func NewDB(db *sql.DB, dialect Dialect) *DB {
return &DB{
DB: db,
dialect: dialect,
plans: make(map[reflect.Type]plan),
}
}
// TODO: remove
func Keks[T IsTable](ctx context.Context, db *DB) error {
_, err := db.getPlan(reflect.TypeFor[T]())
return 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
}
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