hive on tez not convert map join to broadcast join

[r7raul1...@163.com]

In MR query plan is 

Map Join Operator 
condition map: 
Left Outer Join0 to 1 
keys: 
0 ordr_code (type: string), cart_prod_id (type: bigint) 
1 parnt_ordr_code (type: string), comb_prod_id (type: bigint) 
outputColumnNames: _col1, _col2, _col3, _col5, _col10, _col11, _col15, _col16, 

But in tez 

 Reducer 2 <- Map 1 (SIMPLE_EDGE), Map 4 (SIMPLE_EDGE)     No  broadcast edge 
Reducer 3 <- Map 5 (SIMPLE_EDGE), Reducer 2 (SIMPLE_EDGE)

Merge Join Operator 
condition map: 
Left Outer Join0 to 1 
keys: 
0 ordr_code (type: string), cart_prod_id (type: bigint) 
1 parnt_ordr_code (type: string), comb_prod_id (type: bigint)


r7raul1...@163.com