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https://issues.apache.org/jira/browse/IMPALA-7967?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul Rogers reassigned IMPALA-7967:
-----------------------------------
Assignee: (was: Paul Rogers)
> Incorrect decimal size in V2 for a numeric const cast to BIGINT
> ---------------------------------------------------------------
>
> Key: IMPALA-7967
> URL: https://issues.apache.org/jira/browse/IMPALA-7967
> Project: IMPALA
> Issue Type: Bug
> Components: Frontend
> Affects Versions: Impala 3.1.0
> Reporter: Paul Rogers
> Priority: Major
>
> Decimal version 2 introduces revised rules for computing decimal width. For
> example:
> {noformat}
> CAST(1 AS DECIMAL(10, 0)) + CAST(2 AS DECIMAL(19,0)) --> DECIMAL(20,0)
> {noformat}
> The FE uses rules to convert from one type to another. The rule to convert
> from {{BIGINT}} to {{DECIMAL}} is:
> {noformat}
> BIGINT --> DECIMAL(19,0)
> {noformat}
> Put these two together:
> {noformat}
> CAST(1 AS DECIMAL(10, 0)) + CAST(2 AS BIGINT)
> {noformat}
> The result should be {{DECIMAL(20,0)}}. But, because of a bug in the way
> constant folding works, the result is actually {{DECIMAL(11,0)}} as seen in
> {{AnalyzeExprsTest.TestDecimalArithmetic()}}:
> {code:java}
> testDecimalExpr(decimal_10_0 + " + cast(1 as bigint)",
> ScalarType.createDecimalType(11, 0));
> {code}
> It seems one reason the bug was not caught is that the unit tests only check
> for constants, not for columns. Modify the tests to work against
> {{functional.alltypes}} (they currently work without a table), and substitute
> {{bigint_col}} for {{CAST(2 AS BIGINT)}}.
> Expected that the code should have followed the rules described above whether
> the values are a column, or a constant explicitly cast to the same type as
> the column. (Constants without out a cast should follow rules for their
> "natural type" which is what appears to be incorrectly happening in the test
> case above.)
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