-- { echoOn }

EXPLAIN header = 1, optimize = 0 SELECT avgWeighted(x, y) FROM (SELECT NULL, 255 AS x, 1 AS y UNION ALL SELECT y, NULL AS x, 1 AS y);
Expression (Project names)
Header: avgWeighted(x, y) Nullable(Float64)
  Expression (Projection)
  Header: avgWeighted(x_0, y_1) Nullable(Float64)
    Aggregating
    Header: avgWeighted(x_0, y_1) Nullable(Float64)
      Expression (Before GROUP BY)
      Header: x_0 Nullable(UInt8)
              y_1 UInt8
        Expression (Change column names to column identifiers)
        Header: x_0 Nullable(UInt8)
                y_1 UInt8
          Union
          Header: NULL Nullable(UInt8)
                  x Nullable(UInt8)
                  y UInt8
            Expression (Conversion before UNION)
            Header: NULL Nullable(UInt8)
                    x Nullable(UInt8)
                    y UInt8
              Expression (Project names)
              Header: NULL Nullable(Nothing)
                      x UInt8
                      y UInt8
                Expression (Projection)
                Header: NULL_Nullable(Nothing) Nullable(Nothing)
                        255_UInt8 UInt8
                        1_UInt8 UInt8
                  Expression (Change column names to column identifiers)
                  Header: system.one.dummy_0 UInt8
                    ReadFromStorage (SystemOne)
                    Header: dummy UInt8
            Expression (Conversion before UNION)
            Header: NULL Nullable(UInt8)
                    x Nullable(UInt8)
                    y UInt8
              Expression (Project names)
              Header: y UInt8
                      x Nullable(Nothing)
                      y UInt8
                Expression (Projection)
                Header: 1_UInt8 UInt8
                        NULL_Nullable(Nothing) Nullable(Nothing)
                        1_UInt8 UInt8
                  Expression (Change column names to column identifiers)
                  Header: system.one.dummy_0 UInt8
                    ReadFromStorage (SystemOne)
                    Header: dummy UInt8
SELECT avgWeighted(x, y) FROM (SELECT NULL, 255 AS x, 1 AS y UNION ALL SELECT y, NULL AS x, 1 AS y);
255