21.6.7. EJBQL 2.1 and SQL92 queries

The default query compiler doesn't fully support EJB-QL 2.1 or the SQL92 standard. If you need either of these functions, you can replace the query compiler. The default compiler is specified in standardjbosscmp-jdbc.xml. 
<defaults>
    ...
    <ql-compiler>org.jboss.ejb.plugins.cmp.jdbc.JDBCEJBQLCompiler</ql-compiler>
    ...
</defaults>
To use the SQL92 compiler, simply specify the SQL92 compiler in ql-compiler element. 
<defaults>
    ...
    <ql-compiler>org.jboss.ejb.plugins.cmp.jdbc.EJBQLToSQL92Compiler</ql-compiler>
    ...
</defaults>
This changes the query compiler for all beans in the entire system. You can also specify the ql-compiler for each element in jbosscmp-jdbc.xml. Here is an example using one of our earlier queries. 
<query>
    <query-method>
        <method-name>findBadDudes_ejbql</method-name>
        <method-params>
            lt;method-param>int</method-param>
        </method-params>
    </query-method>
    <ejb-ql><![CDATA[
        SELECT OBJECT(g)
        FROM gangster g
        WHERE g.badness > ?1]]>
    </ejb-ql>
    <ql-compiler>org.jboss.ejb.plugins.cmp.jdbc.EJBQLToSQL92Compiler</ql-compiler>
</query>
One important limitation of SQL92 query compiler is that it always selects all the fields of an entity regardless the read-ahead strategy in use. For example, if a query is configured with the on-loadread-ahead strategy, the first query will include all the fields, not just primary key fields but only the primary key fields will be read from the ResultSet. Then, on load, other fields will be actually loaded into the read-ahead cache. The on-findread-ahead with the default load group * works as expected.