Toplink outer join issue using ExpressionBuilder getAlllowingNull

Question

I am trying to retrieve some records through a Toplink outer join expression using ExpressionBuilder's getAllowingNull() with an IN clause but I don't get the correct results.
In my setup I have the following structure
CREATE TABLE BOX
MY_BOX_ID NUMBER(10) PRIMARY KEY
, MY_CODE VARCHAR2(30) NOT NULL CONSTRAINT u_code UNIQUE
CREATE TABLE ITEM
MY_ITEM_ID NUMBER(10) PRIMARY KEY
,MY_TYPE NUMBER(6) NOT NULL
,BOX_ID REFERENCES BOX(MY_BOX_ID)
INSERT INTO BOX values (1, '001');
INSERT INTO ITEM values (1, 1, 1);
INSERT INTO ITEM values (2, 1, null);
The Toplink mappings are the most common ones and the code that retrieves the results is
Vector vals = new Vector();
vals.add(new String('001'));
Vector dbList = null;
try
DatabaseSession dbSession = getToplinkSession();
ReadAllQuery query = new ReadAllQuery();
query.setReferenceClass(Item.class);
ExpressionBuilder expBuilder = new ExpressionBuilder();
Expression exp = expBuilder.getAllowingNull("Box").get("myCode").in(vals);
query.setSelectionCriteria(exp);
dbList = (Vector) dbSession.executeQuery(query);
catch(Exception e)
e.printStackTrace();
When I run the piece of code Toplink generates the following DB query
SELECT t1.MY_ITEM_ID, t1.MY_TYPE FROM BOX t0, ITEM t1 WHERE ((t0.MY_CODE IN ('001')) AND (t0.MY_BOX_ID (+) = t1.BOX_ID))
which returns just the record for which the foreign key is not null
MY_ITEM_ID MY_TYPE
1 1
However I would have expected to get back two records including the one where the foreign key box_id is null. That have happened if the generated SQL would have been:
SELECT t1.MY_ITEM_ID, t1.MY_TYPE FROM BOX t0, ITEM t1 WHERE ((t0.MY_CODE (+) IN ('001')) AND (t0.MY_BOX_ID (+) = t1.BOX_ID))
with the outer join operator applied to the query key as well.
I was wondering if someone could provide some advice on how to get the correct result.
Thanks for any help,
Lucian

Answer 1

Hello,
Calling builder.getAllowingNull("name_of_field_in_MyJDO"); returns an expression that is not used anywhere in the following code, and so it is not used in the query.
The addJoinedAttribute(String) on ReadAllQuery will make a simple join expression using the String as the query key. If you want to use an outerJoin instead of the simple inner join created, try:
readAllQry.addJoinedAttribute(builder.getAllowingNull("name_of_field_in_MyJDO"));
instead. You will also want to remove any joining statements added at the mapping level made in trying to get this to work, otherwise the inner join specified though those options will still be used.
Best Regards,
Chris