[GitHub] [arrow-datafusion] ygf11 commented on a diff in pull request #4826: Support non-tuple expression for in-subquery to join

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ygf11 commented on code in PR #4826:
URL: https://github.com/apache/arrow-datafusion/pull/4826#discussion_r1068006850


##########
datafusion/optimizer/src/decorrelate_where_in.rs:
##########
@@ -554,14 +636,12 @@ mod tests {
             .project(vec![col("customer.c_custkey")])?
             .build()?;
 
-        // Query will fail, but we can still transform the plan
         let expected = "Projection: customer.c_custkey [c_custkey:Int64]\
-        \n  LeftSemi Join: customer.c_custkey = __correlated_sq_1.o_custkey 
[c_custkey:Int64, c_name:Utf8]\
+        \n  LeftSemi Join:  Filter: customer.c_custkey = 
__correlated_sq_1.o_custkey AND customer.c_custkey = customer.c_custkey 
[c_custkey:Int64, c_name:Utf8]\

Review Comment:
   No, I do not handle this special case, just treat `customer.c_custkey = 
customer.c_custkey` as join filter.
   
   I think it is better to add this to the filter of outer table, then the plan 
will be like:
   ```
   "Projection: customer.c_custkey [c_custkey:Int64]\
      LeftSemi Join: customer.c_custkey = __correlated_sq_1.o_custkey 
[c_custkey:Int64, c_name:Utf8]
        Filter: customer.c_custkey = customer.c_custkey [..]\
           TableScan: customer [c_custkey:Int64, c_name:Utf8]\
        SubqueryAlias: __correlated_sq_1 [o_custkey:Int64]\
           Projection: orders.o_custkey AS o_custkey [o_custkey:Int64]\
             TableScan: orders [o_orderkey:Int64, o_custkey:Int64, 
o_orderstatus:Utf8, o_totalprice:Float64;N]"
   ``` 
   
   Is this the right direction?



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