ozankabak commented on code in PR #12003:
URL: https://github.com/apache/datafusion/pull/12003#discussion_r1720839499


##########
datafusion/sqllogictest/test_files/joins.slt:
##########
@@ -3898,6 +3898,7 @@ SELECT * FROM (
 ) as lhs RIGHT JOIN (
     SELECT * from right_table_no_nulls
     ORDER BY b
+    LIMIT 10

Review Comment:
   We can not leave the test as is because the sort in the subquery gets 
optimized away (rightfully), breaking the intent of the test. These kind of 
tests seems to be originally written with the assumption that the sort wouldn't 
be optimized away, and the subquery with ORDER BY was mimicking a table with 
order.
   
   Placing the limit prevents the optimizer from optimizing the sort away, 
keeping the intent of the test intact. Keeping the test as is gives us a 
degenerate test with our new, more powerful optimizer.
   
   Once we get `WITH ORDER` support for memory tables, we will simply use a 
memory table with ordering in these tests, and they will be reverted back fully 
(i.e. the LIMIT will be removed).



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