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https://issues.apache.org/jira/browse/HIVE-18421?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16351212#comment-16351212
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Vihang Karajgaonkar commented on HIVE-18421:
--------------------------------------------
Updated the Jira description appropriately. This patch doesn't add code to
handle overflows in a "right" manner. It only makes vectorized code execution
handle overflow in a "consistent" manner when compared to non-vectorized
execution.
I feel that handling overflows according to a configurable policy (wraparound,
warn, error, set to null) would be a good addition and it can be taken up as a
separate effort.
Attaching the first version of this patch. I reviewed almost all the vector
expressions (phew ..;)) and found a subset of expressions which do not handle
overflows in a consistent manner. As discussed above, it introduces a new
config which enables usage of checked expressions when available.
> Vectorized execution handles overflows in a different manner than
> non-vectorized execution
> ------------------------------------------------------------------------------------------
>
> Key: HIVE-18421
> URL: https://issues.apache.org/jira/browse/HIVE-18421
> Project: Hive
> Issue Type: Bug
> Components: Vectorization
> Affects Versions: 2.1.1, 2.2.0, 3.0.0, 2.3.2
> Reporter: Vihang Karajgaonkar
> Assignee: Vihang Karajgaonkar
> Priority: Major
> Attachments: HIVE-18421.01.patch
>
>
> In vectorized execution arithmetic operations which cause integer overflows
> can give wrong results. Issue is reproducible in both Orc and parquet.
> Simple test case to reproduce this issue
> {noformat}
> set hive.vectorized.execution.enabled=true;
> create table parquettable (t1 tinyint, t2 tinyint) stored as parquet;
> insert into parquettable values (-104, 25), (-112, 24), (54, 9);
> select t1, t2, (t1-t2) as diff from parquettable where (t1-t2) < 50 order by
> diff desc;
> +-------+-----+-------+
> | t1 | t2 | diff |
> +-------+-----+-------+
> | -104 | 25 | 127 |
> | -112 | 24 | 120 |
> | 54 | 9 | 45 |
> +-------+-----+-------+
> {noformat}
> When vectorization is turned off the same query produces only one row.
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