set session max_parallel_workers = 0;

set session join_collapse_limit = 8;
set session geqo_threshold = 12;
set session geqo_effort = 5;

SELECT master_tbl.*
FROM master_tbl
JOIN child_tbl01 ON master_tbl.master_id = child_tbl01.master_id
JOIN child_tbl02 ON child_tbl01.child_id = child_tbl02.master_id
JOIN child_tbl03 ON child_tbl02.child_id = child_tbl03.master_id
JOIN child_tbl04 ON child_tbl03.child_id = child_tbl04.master_id
JOIN child_tbl05 ON child_tbl04.child_id = child_tbl05.master_id
JOIN child_tbl06 ON child_tbl05.child_id = child_tbl06.master_id
JOIN child_tbl07 ON child_tbl06.child_id = child_tbl07.master_id
JOIN child_tbl08 ON child_tbl07.child_id = child_tbl08.master_id
JOIN child_tbl09 ON child_tbl08.child_id = child_tbl09.master_id
JOIN child_tbl10 ON child_tbl09.child_id = child_tbl10.master_id

JOIN child_tbl11 ON child_tbl10.child_id = child_tbl11.master_id
JOIN child_tbl12 ON child_tbl11.child_id = child_tbl12.master_id
JOIN child_tbl13 ON child_tbl12.child_id = child_tbl13.master_id
JOIN child_tbl14 ON child_tbl13.child_id = child_tbl14.master_id
JOIN child_tbl15 ON child_tbl14.child_id = child_tbl15.master_id
JOIN child_tbl16 ON child_tbl15.child_id = child_tbl16.master_id
JOIN child_tbl17 ON child_tbl16.child_id = child_tbl17.master_id
JOIN child_tbl18 ON child_tbl17.child_id = child_tbl18.master_id
JOIN child_tbl19 ON child_tbl18.child_id = child_tbl19.master_id
JOIN child_tbl20 ON child_tbl19.child_id = child_tbl20.master_id

JOIN child_tbl21 ON child_tbl20.child_id = child_tbl21.master_id
JOIN child_tbl22 ON child_tbl21.child_id = child_tbl22.master_id
JOIN child_tbl23 ON child_tbl22.child_id = child_tbl23.master_id
JOIN child_tbl24 ON child_tbl23.child_id = child_tbl24.master_id
JOIN child_tbl25 ON child_tbl24.child_id = child_tbl25.master_id
JOIN child_tbl26 ON child_tbl25.child_id = child_tbl26.master_id
JOIN child_tbl27 ON child_tbl26.child_id = child_tbl27.master_id
JOIN child_tbl28 ON child_tbl27.child_id = child_tbl28.master_id
JOIN child_tbl29 ON child_tbl28.child_id = child_tbl29.master_id
JOIN child_tbl30 ON child_tbl29.child_id = child_tbl30.master_id

JOIN child_tbl31 ON child_tbl20.child_id = child_tbl31.master_id
JOIN child_tbl32 ON child_tbl20.child_id = child_tbl32.master_id
JOIN child_tbl33 ON child_tbl20.child_id = child_tbl33.master_id
JOIN child_tbl34 ON child_tbl20.child_id = child_tbl34.master_id
JOIN child_tbl35 ON child_tbl20.child_id = child_tbl35.master_id
JOIN child_tbl36 ON child_tbl20.child_id = child_tbl36.master_id
JOIN child_tbl37 ON child_tbl20.child_id = child_tbl37.master_id
JOIN child_tbl38 ON child_tbl20.child_id = child_tbl38.master_id
JOIN child_tbl39 ON child_tbl20.child_id = child_tbl39.master_id
JOIN child_tbl40 ON child_tbl30.child_id = child_tbl40.master_id

WHERE
     master_tbl.master_id=1
AND  child_tbl31.child_id=1
AND  child_tbl32.child_id=1
AND  child_tbl33.child_id=1
AND  child_tbl34.child_id=1
AND  child_tbl35.child_id=1
AND  child_tbl36.child_id=1
AND  child_tbl37.child_id=1
AND  child_tbl38.child_id=1
AND  child_tbl39.child_id=1
AND  child_tbl40.child_id=1;