mapToOne<T> method
Given a function mapping the current row to T, transform each emitted Query which returns a single row to T.
It is an StateError for a query to pass through this operator with more than 1 row in its result
set. Use LIMIT 1
on the underlying SQL query to prevent this.
Emits a StateError when result sets has 0 rows.
Implementation
Stream<T> mapToOne<T>(T Function(JSON row) rowMapper) =>
_queryToOneStreamTransformer(this, rowMapper, null);