wangyum opened a new pull request #29728:
URL: https://github.com/apache/spark/pull/29728


   ### What changes were proposed in this pull request?
   
   This pr prohibit binary comparisons chain.
   
   ### Why are the changes needed?
   
   1. There are potential issues in enabling the binary comparison chain. Wrong 
SQL written by users will affect the stability of the entire thrift server 
because of Spark sql will use `BroadcastNestedLoopJoin `. This is a real case:
   
![image](https://user-images.githubusercontent.com/5399861/92910722-e980fc80-f45a-11ea-9e17-5c4ff9eee54f.png)
   
   2. Most SQL engine do not support
   ```
   postgres=# create table t3(a int, b int, c int);
   CREATE TABLE
   postgres=# select * from t3 where a = b =c;
   ERROR:  syntax error at or near "="
   ```
   
   ### Does this PR introduce _any_ user-facing change?
   
   No.
   
   
   ### How was this patch tested?
   
   Unit test.
   


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