xudong963 opened a new issue #1585:
URL: https://github.com/apache/arrow-datafusion/issues/1585


   **Is your feature request related to a problem or challenge? Please describe 
what you are trying to do.**
   Under certain conditions, convert `outer join` to `inner join` to improve 
performance.
   
   **Describe the solution you'd like**
   During predicate pushdown, if the filter condition (`where`) only references 
the **non-nullable-side** table, then it can be pushed down. But if the filter 
condition (`where`) references the **nullable-side** table, it can't be pushed 
down, things get bad, which leads to performance cracking.
   
   Fortunately, if the filtering conditions are **strict**, we can convert the 
**outer join** to **inner join**, all filter conditions can be pushed down.
   
   Broadly speaking, a function, operator, or expression is considered 
**strict** if the input argument is NULL and the output is either NULL or FALSE.
   
   **Describe alternatives you've considered**
   No
   **Additional context**
   AFAIK, Postgres has the feature.


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