How is bushy plans generated in join_search_one_lev

Greeting. 

plans in real life (for example tpc-h Q20) like below. However I don't know

how it is generated with the algorithm in join_search_one_lev since it always

make_rels_by_clause_join with joinrel[1] which is initial_rels which is baserel. 

Am I missing something?

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 Sort
   Sort Key: supplier.s_name
   ->  Nested Loop Semi Join
         ->  Nested Loop
               Join Filter: (supplier.s_nationkey = nation.n_nationkey)
               ->  Index Scan using supplier_pkey on supplier
               ->  Materialize
                     ->  Seq Scan on nation
                           Filter: (n_name = 'KENYA'::bpchar)
         ->  Nested Loop
               ->  Index Scan using idx_partsupp_suppkey on partsupp
                     Index Cond: (ps_suppkey = supplier.s_suppkey)
                     Filter: ((ps_availqty)::numeric > (SubPlan 1))
                     SubPlan 1
                       ->  Aggregate
                             ->  Index Scan using idx_lineitem_part_supp on lineitem
                                   Index Cond: ((l_partkey = partsupp.ps_partkey) AND (l_suppkey = partsupp.ps_suppkey))
                                   Filter: ((l_shipdate >= '01-JAN-97 00:00:00'::timestamp without time zone) AND (l_shipdate < '01-JAN-98 00:00:00'::timestamp without time zone))
               ->  Index Scan using part_pkey on part
                     Index Cond: (p_partkey = partsupp.ps_partkey)
                     Filter: ((p_name)::text ~~ 'lavender%'::text)
(21 rows)

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