[GitHub] [calcite] julianhyde commented on a change in pull request #1117: [CALCITE-2921] support null literal in function call

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julianhyde commented on a change in pull request #1117: [CALCITE-2921] support null literal in function call
URL: https://github.com/apache/calcite/pull/1117#discussion_r309939693
 
 

 ##########
 File path: core/src/test/resources/sql/sub-query.iq
 ##########
 @@ -32,7 +32,7 @@ where t1.x not in (select t2.x from t2);
 (0 rows)
 
 !ok
-EnumerableCalc(expr#0..4=[{inputs}], expr#5=[0], expr#6=[=($t1, $t5)], expr#7=[<>($t1, $t5)], expr#8=[IS NULL($t4)], expr#9=[>=($t2, $t1)], expr#10=[IS NOT NULL($t0)], expr#11=[AND($t7, $t8, $t9, $t10)], expr#12=[OR($t6, $t11)], X=[$t0], $condition=[$t12])
+EnumerableCalc(expr#0..4=[{inputs}], expr#5=[0], expr#6=[=($t1, $t5)], expr#7=[IS NULL($t4)], expr#8=[>=($t2, $t1)], expr#9=[IS NOT NULL($t0)], expr#10=[AND($t7, $t8, $t9)], expr#11=[OR($t6, $t10)], X=[$t0], $condition=[$t11])
 
 Review comment:
   You're right to be concerned. But I did some investigation and I think this is OK.
   
   There are some places in rules (e.g. `SubQueryRemoveRule`) where we create raw null values (using `RelBuilder.literal(null)`). With this new type-inference logic, those null literals can now be converted to typed nulls, and therefore the plans get better.
   
   But we should not be relying on type-inference. I have made a pass over the code to ensure that when we create null literals internally, we give them a type.

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