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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-3652) Derby does not follow the SQL Standard when trying to map SQL routines to Java methods.
Date Fri, 02 May 2008 18:08:55 GMT

     [ https://issues.apache.org/jira/browse/DERBY-3652?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Rick Hillegas updated DERBY-3652:
---------------------------------

    Attachment: derby-3652-01-ab-mixTypesOnFirstPass.diff

Attaching second rev of patch, derby-3652-01-ab-mixTypesOnFirstPass.diff. Again, no new tests
yet. This version passes the regression tests. The first version failed because the database
metadata inspection of indexes ended up relying on there being only one qualifying overload
of IndexDescriptorImpl.getKeyColumnPosition(). Unfortunately, there are two which qualify
under the ANSI method resolution rules, resulting in an ambiguity:

public int getKeyColumnPosition(int heapColumnPosition)
public java.lang.Integer getKeyColumnPosition(java.lang.Integer heapColumnPosition)

That is, internal Derby code relies on non-ANSI method resolution rules. Two approaches to
this problem occurred to me:

1) Rework the internal Derby methods to remove the ambiguities.

2) Make the method resolver sensitive to whether it is resolving an internal Derby method--user
written procedures and functions are not allowed to bind to internal Derby methods.

I thought that (1) was a bit more straightforward but also more likely to have edge cases
which we don't test for today. I opted for (2) as the less risky alternative.


> Derby does not follow the SQL Standard when trying to map SQL routines to Java methods.
> ---------------------------------------------------------------------------------------
>
>                 Key: DERBY-3652
>                 URL: https://issues.apache.org/jira/browse/DERBY-3652
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.5.0.0
>            Reporter: Rick Hillegas
>         Attachments: derby-3652-01-aa-mixTypesOnFirstPass.diff, derby-3652-01-ab-mixTypesOnFirstPass.diff,
SignatureMapping.html, SignatureMapping.html, SignatureProblems.java, signatureProblems.sql
>
>
> I have only tested this in the 10.5 trunk. However, I suspect that this affects all previous
releases of Derby as well.
> In resolving method signatures for function/procedure invocations, the SQL standard makes
the following definitions in part 13, section 4.5 (parameter mapping). These definitions,
in turn, refer to tables B-1 and B-3 in JDBC 3.0 Specification, Final Release, October 2001
([JDBC]).
>     * Simply mappable - This refers to the correspondence of SQL and Java types described
in [JDBC] table B-1. This is the table which defines the mapping of SQL types to Java primitives.
>     * Object mappable - This refers to the correspondence of SQL and Java types described
in [JDBC] table B-3. This is the table which defines the mapping of SQL types to Java wrapper
objects.
>     * Output mappable - For OUT and INOUT parameters, this refers to a single element
array whose cell is simply mappable or object mappable. E.g. Integer[] or float[].
>     * Mappable - This means simply, object, or output mappable.
>     * Result set mappable - This means a single element array whose cell is a type which
implements either java.sql.ResultSet or sqlj.runtime.ResultSetIterator.
> Putting all of this together, section 4.5 continues:
>     "A Java method with M parameters is mappable (to SQL) if and only if, for some N,
0 (zero) <= N <= M, the data types of the first N parameters are mappable, the last
M - N parameters are result set mappable, and the result type is either simply mappable, object
mappable, or void."
> Section 8.6 gives more detailed rules, but they are hard to follow. According to section
8.6, when resolving a routine invocation, Derby should expect to find one and only one static
mappable method with the expected external name (Java class + method name).
> I believe that this is a fair description of the rules. This, at least, is what some
other databases appear to do. See, for instance, http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.help.ase_15.0.java/html/java/java126.htm
and http://www.service-architecture.com/database/articles/mapping_sql_and_java_data_types.html
> We do not have a regression test which verifies that Derby applies the SQL standard resolution
rules. There may be several divergences from the standard. This JIRA is a place to track those
discrepancies. Here is one that I have noticed:
> The following SQL signature
> ( a int ) returns int
> should be mappable to any of the following Java signatures
> public static int f( int a )
> public static int f( Integer a )
> public static Integer f( int a )
> public static Integer f( Integer a )
> However, I observe that Derby is only able to resolve the first and third signatures
(the ones with primitive arguments). I will attach a test case showing this problem.
> I will also attach an html table summarizing the simply and object mappable rules.

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