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https://issues.apache.org/jira/browse/HIVE-6327?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13887281#comment-13887281
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Xuefu Zhang commented on HIVE-6327:
-----------------------------------
I'm not talking about method matching. I'm talking about data type in general.
Double data and decimal data are intrinsically different, and Hive shouldn't
implicit convert from one to the other. An an example, let's say there is a UDF
just returns the input and it only has "double evaluate(double input)" defined.
For this, if user passes decimal input to the UDF, hoping to get its decimal
number back. In this case, I'd argue that Hive should return an error rather
than converting the input to a double and return it. I'd also contend the
reverse is also true. GenericUDF overcomes the shortcomings of UDF, where
everything becomes explicit.
{quote}
I thought the point of FunctionRegistry.getMethodInternal() was to find best
matching method signature given the arguments, while doing type conversion if
necessary.
{quote}
Yes, that's what hive is doing, but it doesn't mean in order to find a match,
any conversion can be performed. And the conversion is implicit. I was arguing
that conversion between double and decimal should be explicit. Thus, when
finding a match, Hive shouldn't treat double and decimal exchangeable,
regardless whether hive is actually doing it or not.
I don't know what this debate is leading to, but Hive has the problem as
described in the JIRA and I'm solving it. If you have any feedback, I'd be
happy to see it once you actually see the solution.
> A few mathematic functions don't take decimal input
> ---------------------------------------------------
>
> Key: HIVE-6327
> URL: https://issues.apache.org/jira/browse/HIVE-6327
> Project: Hive
> Issue Type: Improvement
> Affects Versions: 0.11.0, 0.12.0
> Reporter: Xuefu Zhang
> Assignee: Xuefu Zhang
>
> A few mathematical functions, such as sin() cos(), etc. don't take decimal as
> argument.
> {code}
> hive> show tables;
> OK
> Time taken: 0.534 seconds
> hive> create table test(d decimal(5,2));
> OK
> Time taken: 0.351 seconds
> hive> select sin(d) from test;
> FAILED: SemanticException [Error 10014]: Line 1:7 Wrong arguments 'd': No
> matching method for class org.apache.hadoop.hive.ql.udf.UDFSin with
> (decimal(5,2)). Possible choices: _FUNC_(double)
> {code}
> HIVE-6246 covers only sign() function. The remaining ones, including sin,
> cos, tan, asin, acos, atan, exp, ln, log, log10, log2, radians, and sqrt.
> These are non-generic UDFs.
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