Function join_data_on_field 

pub fn join_data_on_field(
    left: Stream,
    right: Stream,
    left_path: Vec<Symbol>,
    right_path: Vec<Symbol>,
    output_kind: Symbol,
) -> Result<Stream>

Inner-joins two data streams on equal field values.

Both streams are recorded to completion, then every left payload whose value at left_path equals a right payload’s value at right_path emits a packet of output_kind carrying {key, left, right} and the union of both items’ ticks. Both sources must reach done.