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From Mark Rose <mr...@email.arc.nasa.gov>
Subject Using table results dynamically generated by Java classes
Date Thu, 13 Apr 2006 21:43:27 GMT
I'm interested in importing data into Derby databases from other  
sources, and the ability in Derby to have Java classes return  
ResultSets that can be used as dynamic tables seemed promising:

INSERT INTO sometable
FROM new somejavaclass(constructorParameters) t;

The class "somejavaclass" must implement java.sql.ResultSet.

I've gotten it to work, but only by having my class be in some  
subpackage of org.apache.derby.diag. There is code in the parser  
source that implements a special check if the java class is not in  
one of a few special packages (sqlgrammer.jj line 1644):

if (!javaClassName.startsWith("org.apache.derby.diag.") && ! 
javaClassName.startsWith("org.apache.derby.catalog.") && ! 

I don't like the fact that I must have my class in some special  
package, but I haven't been able to find out how to turn off the  
check for "foreign" Java classes. (It seems to be hard-coded in  
CompilerContext, checking for the bit INTERNAL_SQL_ILLEGAL in the  
flag set by setReliability().)

Does anyone know how to turn off this test so my class doesn't have  
to live in the Derby tree?

BTW, I realize you can do something similar with "CREATE PROCEDURE",  
but it seems you lose the ability to choose which columns you want-- 
or have to implement the selection yourself in Java--, and you can't  
join with other tables, etc., so I'd prefer to use the "FROM new  
javaclass()" form, if possible.

Mark Rose
QSS Group, Inc. / NASA Ames Research Center

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