Arroyo’s Scalar function implementations are based on Apache DataFusion and these docs are derived from the DataFusion function reference.

​
struct

Returns an Arrow struct using the specified input expressions. Fields in the returned struct use the cN naming convention. For example: c0, c1, c2, etc. 
struct(expression1[, ..., expression_n])
For example, this query converts two columns a and b to a single column with a struct type of fields c0 and c1: 
select * from t;
+---+---+
| a | b |
+---+---+
| 1 | 2 |
| 3 | 4 |
+---+---+

select struct(a, b) from t;
+-----------------+
| struct(t.a,t.b) |
+-----------------+
| {c0: 1, c1: 2}  |
| {c0: 3, c1: 4}  |
+-----------------+

​
Arguments

  • expression_n: Expression to include in the output struct. Can be a constant, column, or function, and any combination of arithmetic or string operators.