[jira] [Commented] (CALCITE-3457) RexSimplify incorrectly simplifies IS NOT NULL operator with ITEM call

["Danny Chen (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-3457?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16964494#comment-16964494 ] 

Danny Chen commented on CALCITE-3457:
-------------------------------------

Okey, it seems that CALCITE-2695 has breaks the Strong semantics somehow for operands with casts. So, at some point, the assertion is still valuable because it helps to find this problem. Maybe we can tweak CALCITE-2695 to have its simplification but still keep the Strongness.

> RexSimplify incorrectly simplifies IS NOT NULL operator with ITEM call
> ----------------------------------------------------------------------
>
>                 Key: CALCITE-3457
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3457
>             Project: Calcite
>          Issue Type: Bug
>    Affects Versions: 1.22.0
>            Reporter: Vova Vysotskyi
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.22.0
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> In CALCITE-3390 ITEM was marked with {{Policy.ANY}} strong policy, but according to its JavaDoc, the result may be null if and only if at least one of its arguments is null. This statement was used in {{RexSimplify.simplifyIsNotNull()}} method, so {{t1.c_nationkey[0] is not null}} will be simplified to {{IS NOT NULL($0)}} which is wrong, since array may be empty, or index may be less than the size of the array.
> Unit test which helps to reproduce this issue:
> {noformat}
>   @Test public void testSimplifyItemIsNotNull() {
>     String query = "select * from sales.customer as t1 where t1.c_nationkey[0] is not null";
>     sql(query)
>         .withTester(t -> createDynamicTester())
>         .withRule(ReduceExpressionsRule.FILTER_INSTANCE)
>         .check();
>   }
> {noformat}
> Returns plan with incorrectly simplified ITEM expression:
> {noformat}
> LogicalProject(**=[$1])
>   LogicalFilter(condition=[IS NOT NULL($0)])
>     LogicalTableScan(table=[[CATALOG, SALES, CUSTOMER]])
> {noformat}
> But the initial intention of CALCITE-3390 was to allow pushing ITEM expression to the right input of left-outer-join.
> I propose to add a new element to the {{Policy}} which will have a relaxed condition - expression is null if at least one of its arguments is null.



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