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From "A B (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-1904) COALESCE with NULL parameter problem
Date Tue, 03 Oct 2006 16:14:24 GMT
    [ http://issues.apache.org/jira/browse/DERBY-1904?page=comments#action_12439557 ] 
            
A B commented on DERBY-1904:
----------------------------

Thanks for continuing to investigate this problem, Cédric.

> I can confirm that in your JDBC Client driver source, the case where arg is null in the
> method setObject(idx, arg) is not treated.  Your should call internally in this case
the
> method setNull(idx, type); 

The problem with this approach is that we don't know what "type" should be.  If the object
in setObject(idx, arg) is a Java null, how does one figure out the corresponding SQL type?

I know very (very) little about what JDBC expects here, but I did look at the JDBC API for
1.4.2 and the description of setObject(parameterIndex, x) says the following:

"The JDBC specification specifies a standard mapping from Java Object types to SQL types.
The given argument will be converted to the corresponding SQL type before being sent to the
database. [...]  This method throws an exception if there is an ambiguity, for example, if
the object is of a class implementing more than one of the interfaces named above."

Does JDBC specify a mapping for a typeless null Java object?  If not, that seems to suggest
"ambiguity" to me and hence Derby would be doing the right thing by throwing an exception.
 But again, I don't know enough about JDBC to say for sure.

Note that there is another JDBC call, setObject(parameterIndex, x, targetSqlType), which allows
the caller to explicitly give a target SQL type, thus removing ambiguity.  In that case Derby
correctly binds the parameter and executes without error (I wrote up a quick test to verify)...

> COALESCE with NULL parameter problem
> ------------------------------------
>
>                 Key: DERBY-1904
>                 URL: http://issues.apache.org/jira/browse/DERBY-1904
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC, SQL
>    Affects Versions: 10.1.3.1
>         Environment: Windows 2000 SP4
> JSTL 1.0.6 on J2EE 1.3
> Tomcat 5.0.28  using a SUN JVM 1.4.2_03
>            Reporter: Cédric Gérard
>            Priority: Blocker
>         Attachments: dblook.log, stackfromderby.log
>
>
> Hi,
> My  initial objective was to execute this query with  the JSTL sql tag library  :
>   
> SELECT  ID_ITM, ITM_NAME, ITM_CODE
>     FROM  ITEMS
>     WHERE  ITM_CODE = COALESCE(?,ITM_CODE)
>   
> ITM_CODE is a NUMERIC column, here's the DDL script of the ITEMS  table :
> CREATE  TABLE  ITEMS (  
>          ID_ITM                BIGINT NOT  NULL  GENERATED ALWAYS AS  IDENTITY, 
>          ITM_CODE         NUMERIC  (22) NOT  NULL
>  );
> When ITM_CODE is not set in my application, JSTL bind the parameter as null. When ITM_CODE
is set, it works.
>   
>  I  got this message error : 
>  : Invalid  data conversion: Parameter object type is invalid for requested conversion.
 (Apache
> Derby  release 10.1.3.1 client  driver)
> => We try to use CAST(? AS NUMERIC) in place of ?. We obtain the same error when NULL
is passed.
>  : The  exception 'java.lang.ArrayIndexOutOfBoundsException: -1' was thrown while  evaluating
> an expression. SQLSTATE: XJ001: Java exception: '-1:  java.lang.ArrayIndexOutOfBoundsException'.
> (Apache Derby snapshot-10.2.0.4  client driver)
> With ij, we have the same problem (but not the same message)
> ij> SELECT ID_ITM, ITM_NAME, ITM_CODE
>      FROM ITEMS
>      WHERE ITM_CODE = COALESCE(NULL,ITM_CODE );
> ERROR 42X01: Syntax error: Encountered "NULL" at line 3, column 31.
> ij> SELECT ID_ITM, ITM_NAME, ITM_CODE
>      FROM ITEMS
>      WHERE ITM_CODE = COALESCE(NULLIF(1,1),ITM_CODE );
> ID_ITM              |ITM_NAME                                          |ITM_CODE
> ------------------------------------------------------------------------------------------------
> ERROR 38000: The exception 'java.lang.NullPointerException' was thrown while evaluating
an expression. SQLSTATE: XJ001: Java exception: ': java.lang.NullPointerException'.
> ij> SELECT ID_ITM, ITM_NAME, ITM_CODE
>      FROM ITEMS
>      WHERE ITM_CODE = COALESCE(CAST(NULLIF(1,1) AS BIGINT), ITM_CODE);
> ID_ITM              |ITM_NAME                                          |ITM_CODE
> ------------------------------------------------------------------------------------------------
> ERROR 38000: The exception 'java.lang.NullPointerException' was thrown while evaluating
an expression. SQLSTATE: XJ001: Java exception: ': java.lang.NullPointerException'.
> We have the same errors using 10.2.0.4 snapshot.
> The coalesce function should accept NULL parameter.
> Of course, My sample is very simple and I have n search criteria; so I don't want to
create 2^n SQL queries to deal with null or not null criterion.
> I try to replace the coalesce function with a CASE statement but I encountered the same
problems...
> So I don't actually have any workaround.
> Regards,
> Cédric

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