A left join B on A.x=B.x and A.y=B.y
B.x and B.y make result tuple number scale out.
suppose A is scaled out by B.x N1 time, and scaled out by B.y N2 time, and N1 < N2.
we should choose N1 as the final scale out factor, not N2.
this pr impact on tpcds_sf100 59/17/29/25/47/40/54
before
query59 77295 75279 75230 75230
query17 22642 21566 21599 21566
query29 16508 16092 16006 16006
query25 20262 20571 21171 20571
query47 23571 23264 23107 23107
query40 3305 2849 3064 2849
query54 9052 8882 8715 8715
Total cold run time: 172635 ms
Total hot run time: 168044 ms
after
query59 56435 54717 53919 53919
query17 24167 22377 23237 22377
query29 16950 18325 16333 16333
query25 21478 22975 21358 21358
query47 24412 24611 23920 23920
query40 5491 4779 5176 4779
query54 8671 8664 8658 8658
Total cold run time: 157604 ms
Total hot run time: 151344 ms
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