ydb/yql/essentials/tests/s-expressions/suites/Optimizers/EmptyOverListWithComplexUniq.yqls

(
(let config (DataSource 'config))
(let res_sink (DataSink 'result))

(let list (AsList
    (AsStruct '('key (Uint32 '1)) '('value (Uint32 '2)))
    (AsStruct '('key (Uint32 '2)) '('value (Uint32 '3)))
))

(let res (Aggregate list '('key 'value) '() '()))
(let res (Map res (lambda '(item)
    (AsStruct
        '('composite (AsStruct
            '('k (Member item 'key))
            '('v (Member item 'value))
        ))
        '('key (Member item 'key))
        '('value (Member item 'value))
    )
)))
(let res (Take res (Uint64 '0)))
(let res (FlatMap res (lambda '(item)
    (Just (AsStruct
        '('packed (StablePickle (Member item 'composite)))
        '('composite (Member item 'composite))
        '('key (Member item 'key))
        '('value (Member item 'value))
    ))
)))
(let world (Write! world res_sink (Key) res '('('type))))
(let world (Commit! world res_sink))
(return world)
)