diff options
Diffstat (limited to 'select.go')
| -rw-r--r-- | select.go | 56 |
1 files changed, 38 insertions, 18 deletions
@@ -9,6 +9,8 @@ import ( "errors" "fmt" "reflect" + + . "go.xyrillian.de/gg/option" ) // Select executes the provided SQL query and fills an instance of the record type R for each row in the result set, @@ -158,24 +160,26 @@ func collectRow(rows *sql.Rows, plan plan, v reflect.Value, slots []any, indexes // SelectOne executes the provided SQL query and fills an instance of the record type R if there is exactly one row in the result set, // according to the column names reported by the database as part of the result set. // -// If there are no rows in the result set, [sql.ErrNoRows] is returned. +// If there are no rows in the result set, [None] is returned. // // Warning: Because of limitations in the interface of database/sql, this function is built on [Store.Select] and cannot be any faster than it. // For maximum performance, use [Store.SelectOneWhere] which avoids the overhead of potentially having to read multiple rows. -func (s Store[R]) SelectOne(ctx context.Context, db Handle, query string, args ...any) (result R, err error) { +func (s Store[R]) SelectOne(ctx context.Context, db Handle, query string, args ...any) (Option[R], error) { // NOTE: This function body should be as short as possible to reduce the binary size after monomorphization. // Any expression that does not depend on type R should be factored out into a reusable function. - - var results []R - results, err = s.Select(ctx, db, query, args...) - if err == nil { - if len(results) == 0 { - err = sql.ErrNoRows - } else { - result = results[0] - } + // + // NOTE: The "limitation in the interface of database/sql" is that type sql.Row does not have the Columns() method, + // which we need when mapping result columns to struct fields for user-provided queries. + + results, err := s.Select(ctx, db, query, args...) + switch { + case err != nil: + return None[R](), err + case len(results) == 0: + return None[R](), nil + default: + return Some(results[0]), nil } - return } // SelectOneWhere is like [Store.SelectOne], but you only provide the part of the SELECT query that comes after the WHERE. @@ -183,12 +187,20 @@ func (s Store[R]) SelectOne(ctx context.Context, db Handle, query string, args . // // This method is more efficient than [Store.SelectOne] on CPU runtime, but has a slight memory allocation overhead per call from query preparation. // This can be avoided by using [Store.PrepareSelectQueryWhere] instead. -func (s Store[R]) SelectOneWhere(ctx context.Context, db Handle, partialQuery string, args ...any) (result R, err error) { +func (s Store[R]) SelectOneWhere(ctx context.Context, db Handle, partialQuery string, args ...any) (Option[R], error) { // NOTE: This function body should be as short as possible to reduce the binary size after monomorphization. // Any expression that does not depend on type R should be factored out into a reusable function. - err = selectOneWhere(ctx, db, s.plan, reflect.ValueOf(&result).Elem(), partialQuery, args) - return + var result R + err := selectOneWhere(ctx, db, s.plan, reflect.ValueOf(&result).Elem(), partialQuery, args) + switch { + case err == nil: + return Some(result), nil + case errors.Is(err, sql.ErrNoRows): + return None[R](), nil + default: + return None[R](), err + } } func selectOneWhere(ctx context.Context, db Handle, plan plan, v reflect.Value, partialQuery string, args []any) error { @@ -271,10 +283,18 @@ func (q PreparedSelectQuery[R]) Select(ctx context.Context, db Handle, args ...a } // SelectOne behaves the same as [Store.SelectOneWhere], but uses the query that was precomputed when q was constructed. -func (q PreparedSelectQuery[R]) SelectOne(ctx context.Context, db Handle, args ...any) (result R, err error) { +func (q PreparedSelectQuery[R]) SelectOne(ctx context.Context, db Handle, args ...any) (Option[R], error) { // NOTE: This function body should be as short as possible to reduce the binary size after monomorphization. // Any expression that does not depend on type R should be factored out into a reusable function. - err = selectOne(ctx, db, q.store.plan, reflect.ValueOf(&result).Elem(), q.query, args) - return + var result R + err := selectOne(ctx, db, q.store.plan, reflect.ValueOf(&result).Elem(), q.query, args) + switch { + case err == nil: + return Some(result), nil + case errors.Is(err, sql.ErrNoRows): + return None[R](), nil + default: + return None[R](), err + } } |