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https://issues.apache.org/jira/browse/HIVE-5436?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13808625#comment-13808625
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Hari Sankar Sivarama Subramaniyan commented on HIVE-5436:
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[~xuefu] Reasons why I thought of fixing the consistency first:
1. I wanted to see how the intermediate results are handled in case of
numericals. For example, for tiny int (1228+1228)/20 will lead to a in-range
result, where as the intermediate result 1228+1228 will be a non tiny int.
This scenario will be very common in case of exponential notation.
2. HIVE-5382 will need a baseline to compare the string cast results with
non-string cast results. My plan was to use testcases like this :
select cast('-1.5e2' as int)-cast(-1.5e2 as int) from tmp and verify that the
result is always 0. This will ensure consistency across cast from
string->numericals (and will expose any existing bugs which is fixed in future
for only one of the cast types since the non-string cast and string cast are
handled separately).
> Hive's casting behavior needs to be consistent
> ----------------------------------------------
>
> Key: HIVE-5436
> URL: https://issues.apache.org/jira/browse/HIVE-5436
> Project: Hive
> Issue Type: Bug
> Reporter: Hari Sankar Sivarama Subramaniyan
> Assignee: Hari Sankar Sivarama Subramaniyan
> Priority: Critical
>
> Hive's casting behavior is inconsistent and the behavior of casting from one
> type to another undocumented as of now when the casted value is out of range.
> For example, casting out of range values from one type to another can result
> in incorrect results.
> Eg:
> 1. select cast('1000' as tinyint) from t1;
> NULL
> 2. select 1000Y from t1;
> FAILED: SemanticException [Error 10029]: Line 1:7 Invalid numerical constant
> '1000Y'
> 3. select cast(1000 as tinyint) from t1;
> -24
> 4.select cast(1.1e3-1000/0 as tinyint) from t1;
> 0
> 5. select cast(10/0 as tinyint) from pw18;
> -1
> The hive user can accidently try to typecast an out of range value. For
> example in the e.g. 4/5 even though the final result is NaN, Hive can
> typecast to a random result. Either we should document that the end user
> should take care of overflow, underflow, division by 0, etc. by
> himself/herself or we should return NULLs when the final result is out of
> range.
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