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https://issues.apache.org/jira/browse/FLINK-34656?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17826917#comment-17826917
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Benchao Li commented on FLINK-34656:
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Although the {{resultTerm}} is a default value instead of {{NULL}}, the
{{nullTerm}} is correct, the the {{GeneratedExpression}} for
{{generateArrayElementAt}} should be correct. Could you provide a test case
that reproduce the problem you described?
> Generated code for `ITEM` operator should return null when getting element of
> a null map/array/row
> --------------------------------------------------------------------------------------------------
>
> Key: FLINK-34656
> URL: https://issues.apache.org/jira/browse/FLINK-34656
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Planner
> Affects Versions: 1.20.0
> Reporter: yisha zhou
> Priority: Major
>
> In FieldAccessFromTableITCase we can find that the expected result of f0[1]
> is null when f0 is a null array.
> However, behavior in generated code for ITEM is not consistent with case
> above. The main code is:
>
> {code:java}
> val arrayAccessCode =
> s"""
> |${array.code}
> |${index.code}
> |boolean $nullTerm = ${array.nullTerm} || ${index.nullTerm} ||
> | $idxStr < 0 || $idxStr >= ${array.resultTerm}.size() || $arrayIsNull;
> |$resultTypeTerm $resultTerm = $nullTerm ? $defaultTerm : $arrayGet;
> |""".stripMargin {code}
> If `array.nullTerm` is true, a default value of element type will be
> returned, for example -1 for null bigint array.
> The reason why FieldAccessFromTableITCase can get expected result is that the
> ReduceExpressionsRule generated an expression code for that case like:
> {code:java}
> boolean isNull$0 = true || false ||
> ((int) 1) - 1 < 0 || ((int) 1) - 1 >=
> ((org.apache.flink.table.data.ArrayData) null).size() ||
> ((org.apache.flink.table.data.ArrayData) null).isNullAt(((int) 1) - 1);
> long result$0 = isNull$0 ? -1L : ((org.apache.flink.table.data.ArrayData)
> null).getLong(((int) 1) - 1);
> if (isNull$0) {
> out.setField(0, null);
> } else {
> out.setField(0, result$0);
> } {code}
> The reduced expr will be a null literal.
>
> I think the behaviors for getting element of a null value should be unified.
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