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

(
# read data from Input table
(let config (DataSource 'config))

(let res_sink (DataSink 'result))

(let str1 (AsStruct '('a (Uint32 '1)) '('b (String 'a))))
(let str2 (AsStruct '('a (Uint32 '2)) '('b (String 'b))))
(let list (AsList str1 str2))

(let res (FlatMap (FlatMap (Iterator list (DependsOn (String '1))) (lambda '(r) (OptionalIf (> (Member r 'a) (Uint32 '0)) r))) (lambda '(r) (ToStream (Just r)))))
(let world (Write! world res_sink (Key) (ForwardList res) '()))

(let res (FlatMap (FlatMap (Iterator list (DependsOn (String '2))) (lambda '(r) (OptionalIf (> (Member r 'a) (Uint32 '0)) r))) (lambda '(r) (AsList r r))))
(let world (Write! world res_sink (Key) (ForwardList res) '()))

(let res (FlatMap (FlatMap (Iterator list (DependsOn (String '3))) (lambda '(r) (OptionalIf (> (Member r 'a) (Uint32 '0)) r))) (lambda '(r) (OptionalIf (> (Member r 'b) (String 'a)) r))))
(let world (Write! world res_sink (Key) (ForwardList res) '()))

(let res (FlatMap (FlatMap (Iterator list (DependsOn (String '4))) (lambda '(r) (ListIf (> (Member r 'a) (Uint32 '0)) r))) (lambda '(r) (ToStream (Just r)))))
(let world (Write! world res_sink (Key) (ForwardList res) '()))

(let res (FlatMap (FlatMap (Iterator list (DependsOn (String '5))) (lambda '(r) (ListIf (> (Member r 'a) (Uint32 '0)) r))) (lambda '(r) (AsList r r))))
(let world (Write! world res_sink (Key) (ForwardList res) '()))

(let res (FlatMap (FlatMap (Iterator list (DependsOn (String '6))) (lambda '(r) (ListIf (> (Member r 'a) (Uint32 '0)) r))) (lambda '(r) (OptionalIf (> (Member r 'b) (String 'a)) r))))
(let world (Write! world res_sink (Key) (ForwardList res) '()))

(let world (Commit! world res_sink))
(return world)
)