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https://issues.apache.org/jira/browse/FLINK-40338?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18102303#comment-18102303
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sepuri sai krishna commented on FLINK-40338:
--------------------------------------------
I reported this issue and asked to be assigned on Aug 5 (comment above) with a
fix and regression tests already prepared locally. PR #28931 was opened ~12
hours later by another contributor while the ticket was still unassigned, and
its description and commit message restate the root-cause analysis from this
ticket's description.
I'd like to submit my patch as originally requested — could a committer assign
this ticket? Happy to review [~hulincup]'s PR instead if the committers prefer
to proceed with it; I mainly want the process followed so the same thing
doesn't happen on the next ticket I file.
> ELT() throws ClassCastException when the index argument is not INT
> ------------------------------------------------------------------
>
> Key: FLINK-40338
> URL: https://issues.apache.org/jira/browse/FLINK-40338
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Runtime
> Affects Versions: 2.0.0, 2.1.0, 2.2.0, 2.3.0
> Reporter: sepuri sai krishna
> Priority: Major
> Labels: pull-request-available
>
> {{ELT}} accepts any {{INTEGER_NUMERIC}} index. {{IndexArgumentTypeStrategy}}
> returns the argument's own data type unchanged (no implicit cast to {{INT}}),
> and the documentation lists the supported signatures as:
> {noformat}
> index <TINYINT | SMALLINT | INTEGER | BIGINT>, expr <CHAR | VARCHAR>, exprs
> <CHAR | VARCHAR>
> index <TINYINT | SMALLINT | INTEGER | BIGINT>, expr <BINARY | VARBINARY>,
> exprs <BINARY | VARBINARY>
> {noformat}
> But {{EltFunction#eval}} indexes the varargs array with {{exprs[(int) index -
> 1]}}, where {{index}} is declared as {{java.lang.Number}}. Per JLS 5.5,
> casting a {{Number}} reference to {{int}} compiles to a narrowing reference
> conversion to {{Integer}} followed by unboxing, i.e. {{((Integer)
> index).intValue()}}. The call therefore succeeds only when the boxed value is
> exactly an {{Integer}}; a {{Byte}}, {{Short}} or {{Long}} fails the
> {{checkcast}}.
> h3. Reproducer
> {code:sql}
> SELECT ELT(CAST(2 AS BIGINT), 'scala', 'java');
> {code}
> {noformat}
> java.lang.ClassCastException: class java.lang.Long cannot be cast to class
> java.lang.Integer
> {noformat}
> Same for {{CAST(2 AS TINYINT)}} and {{CAST(2 AS SMALLINT)}}.
> h3. Why this was not caught
> The out-of-range guard above the cast uses {{index.longValue()}}, so
> out-of-range indices of any type still return {{NULL}} correctly. The
> exception only fires on the success path, when {{1 <= index <= number of
> expressions}}. That is why the existing test {{ELT(9223372036854775807, 'ab',
> 'b')}} passes -- it returns {{NULL}} before ever reaching the cast. Every
> other existing test uses an {{INT}} literal.
> h3. Fix
> Narrow the already-unboxed {{long idx}} rather than casting the {{Number}}
> reference.
> Present since FLINK-35987 introduced ELT; confirmed absent from release-1.20
> and present from release-2.0.
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