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

["Vladimir Sitnikov (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-3457?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17224481#comment-17224481 ] 

Vladimir Sitnikov commented on CALCITE-3457:
--------------------------------------------

Hey [~volodymyr], [~danny0405], it has been a long week :)
Do you think you could have some cycles to analyze what causes an assertion error in https://github.com/apache/calcite/blob/b20e0bf6ca9b605fa4a6203bd06454abd6a98ce2/core/src/test/java/org/apache/calcite/rex/RexProgramTest.java#L512-L519 ?

> 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
>            Assignee: Danny Chen
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.22.0
>
>          Time Spent: 1h 20m
>  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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