Error when forcing checkCacheoOnly

Question

This is a routine we are using to create a named query:
public ObjectLevelReadQuery getResponsibleRolesForRegion()
ReadAllQuery lQuery = new ReadAllQuery();
ExpressionBuilder lBuilder1 = new ExpressionBuilder();
ExpressionBuilder lBuilder2 = new ExpressionBuilder();
ExpressionBuilder lBuilder3 = new ExpressionBuilder();
ReportQuery lSubQuery = new ReportQuery(Employee.class, lBuilder2);
Expression lExpression = null;
lSubQuery.checkCacheOnly();
lSubQuery.setSelectionCriteria((lBuilder2.get("region").equal(lBuilder1.getParameter("region"))).and(lBuilder1.get("userFlag").equal(lBuilder1.getParameter("userFlag"))));
lExpression = lBuilder3.in(lSubQuery);
lQuery.setName("GetResponsibleRolesForRegion");
lQuery.setReferenceClass(Role.class);
lQuery.checkCacheOnly();
lQuery.setSelectionCriteria(lExpression);
lQuery.addArgument("region");
lQuery.addArgument("userFlag");
return lQuery;
when we run this query we get the following error:
Exception EXCEPTION [TOPLINK-6074] (TopLink - 9.0.3.6 (Build 437)): oracle.toplink.exceptions.QueryException
EXCEPTION DESCRIPTION: This expression cannot determine if the object conforms in memory. You must set the query to check the database.
Can we get a better explanation of what it means to conform in memory? Also, are there some guidelines as to how to use queries and the checkCacheOnly feature? Is the in() method somehow preventing the query from being a cache only query?

Answer 1

Hi Mike,
an object conforming in memory is one that is 'in aggreement or harmony with' the selection criteria.
If this can not be determined for any object in-memory, that means the selection criteria was too complicated.
The developers guide contains a list of what expressions can be conformed in-memory.
In general TopLink handles OO expressions well.
employee.get("address").get("city").equals("Ottawa")
mirrors
employee.getAddress().getCity().equals("Ottawa")
so can be conformed naturally by TopLink on objects in the cache.
Subqueries and ReportQueries however are not OO and instead were added to support the full richness of SQL. Expressions containing these are better executed on the database.