Method Query

storage/storage.go:258–323

Query implements read-only query feature.

(ctx context.Context, queries []Query)

// Query implements read-only query feature.
func (s *Storage) Query(ctx context.Context, queries []Query) (columns []string, types []string,
	data [][]interface{}, err error) {
	data = make([][]interface{}, 0)

	if len(queries) == 0 {
		return
	}

	var tx *sql.Tx
	var txOptions = &sql.TxOptions{
		ReadOnly: true,
	}

	if tx, err = s.db.BeginTx(ctx, txOptions); err != nil {
		return
	}

	// always rollback on complete
	defer tx.Rollback()

	q := queries[len(queries)-1]

	// convert arguments types
	args := make([]interface{}, len(q.Args))

	for i, v := range q.Args {
		args[i] = v
	}

	var rows *sql.Rows
	if rows, err = tx.Query(q.Pattern, args...); err != nil {
		return
	}

	// free result set
	defer rows.Close()

	// get rows meta
	if columns, err = rows.Columns(); err != nil {
		return
	}

	// if there is empty columns, treat result as empty
	if len(columns) == 0 {
		return
	}

	// get types meta
	if types, err = s.transformColumnTypes(rows.ColumnTypes()); err != nil {
		return
	}

	rs := newRowScanner(len(columns))

	for rows.Next() {
		err = rows.Scan(rs.ScanArgs()...)
		if err != nil {
			return