Function process_flat_map_row 

fn process_flat_map_row<T>(
    input_row: &RowRef,
    time: &T,
    diff: &Diff,
    exprs: &[LirScalarExpr],
    func: &TableFunc,
    mfp_plan: &MfpPlan<LirScalarExpr>,
    until: &Antichain<Timestamp>,
    datums: &mut DatumVec,
    datums_mfp: &mut DatumVec,
    table_func_output: &mut Vec<(Row, Diff)>,
    ok_session: &mut Session<'_, '_, T, ConsolidatingColumnBuilder<Row, T, Diff>, Capability<T>>,
    err_session: &mut Session<'_, '_, T, ConsolidatingContainerBuilder<Vec<(DataflowErrorSer, T, Diff)>>, Capability<T>>,
    budget: &mut usize,
)
where
    T: RenderTimestamp,

Expands one input record’s table function and drains it through the mfp.

The expansion is chunked so drain_through_mfp amortizes the input-row decode. Argument or function evaluation errors emit to the err session and return early.