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// SPDX-FileCopyrightText: 2026 Stefan Majewsky <majewsky@gmx.net>
// SPDX-License-Identifier: Apache-2.0
package oblast
import (
"context"
"fmt"
"reflect"
)
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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