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https://issues.apache.org/jira/browse/DERBY-3119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12534941
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Alan Burlison commented on DERBY-3119:
--------------------------------------
See also http://blog.tremend.ro/2006/10/03/about-the-maturity-of-apache-derby/:
"It is important to know that Derby has a limited number of built-in functions,
so one needs to frequently resort to custom stored functions. The problem with
this is that, besides the lack of proper documentation, this support is quite
limited. Stored functions can be defined only in Java. That would be mostly
fine if it would work well. But for instance, if you want a stored function
that returns an INTEGER value, you must specify the return type of the
associated Java method as int. This means that basically you cannot return NULL
integers from your function!"
> Derby does not resolve functions to methods with Integer return type.
> ---------------------------------------------------------------------
>
> Key: DERBY-3119
> URL: https://issues.apache.org/jira/browse/DERBY-3119
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.1.1.0, 10.1.2.1, 10.1.3.1, 10.2.1.6, 10.2.2.0,
> 10.3.1.4
> Reporter: Rick Hillegas
>
> Derby can bind a function invocation to a method which returns int but not to
> a method which returns Integer. I think that both of these resolutions should
> succeed given the rules in the SQL Standard, part 13, section 8.6, syntax
> rule 5, case a, item ii. Here is some code which shows this problem. First a
> class to declare the methods:
> public class zz
> {
> public static int returnsInt()
> {
> return 1;
> }
>
> public static Integer returnsInteger()
> {
> return new Integer( 2 );
> }
>
> }
> The following ij script shows that the int-returning method is resolved but
> not the Integer-returning method:
> ij version 10.4
> ij> connect 'jdbc:derby:derby10.4;create=true';
> WARNING 01J01: Database 'derby10.4' not created, connection made to existing
> database instead.
> ij> drop function returnsInt;
> 0 rows inserted/updated/deleted
> ij> drop function returnsInteger;
> 0 rows inserted/updated/deleted
> ij> create function returnsInt()
> returns int
> language java
> parameter style java
> no sql
> external name 'zz.returnsInt'
> ;
> 0 rows inserted/updated/deleted
> ij> create function returnsInteger()
> returns int
> language java
> parameter style java
> no sql
> external name 'zz.returnsInteger'
> ;
> 0 rows inserted/updated/deleted
> ij> values ( returnsInt() );
> 1
> -----------
> 1
> 1 row selected
> ij> values ( returnsInteger() );
> ERROR 42X50: No method was found that matched the method call int
> zz.returnsInteger(), tried all combinations of object and primitive types and
> any possible type conversion for any parameters the method call may have.
> The method might exist but it is not public and/or static, or the parameter
> types are not method invocation convertible.
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