ydb/yql/essentials/tests/s-expressions/suites/Builtins/UnionAll.yql

(
#comment
(let mr_source (DataSource 'yt 'plato))
(let x (Read! world mr_source (Key '('table (String 'Input))) '('key 'subkey 'value) '()))
(let world (Left! x))
(let table1 (Right! x))
(let list1 (Map table1 (lambda '(row) (block '(
    (let res (AsStruct '('foo (FromString (Member row 'key) 'Int32)) '('bar (FromString (Member row 'subkey) 'Int32))))
    (return res)
)
))))
(let x (Read! world mr_source (Key '('table (String 'Input))) '('key 'subkey 'value) '()))
(let world (Left! x))
(let table2 (Right! x))
(let list2 (Map table2 (lambda '(row) (block '(
    (let res (AsStruct '('foo (FromString (Member row 'key) 'Double)) '('jar (Member row 'value))))
    (return res)
)
))))
(let result (UnionAll list1 list2))
(let res_sink (DataSink 'result))
(let world (Write! world res_sink (Key) (FormatType (TypeOf result)) '()))
(let world (Write! world res_sink (Key) result '()))
(let world (Commit! world res_sink))
(return world)
)