> Can you give a specific example where INNER JOIN would give the wrong answer? There are likely many examples over the 8 years that this query generation mechanism has been in place; all defaults have been set based on what was needed to get a reliable mechanism for the vast majority of queries (and to cater for JDOQL and JPQL). I don't have time to go back through old history and work out some.
What you can do is get the latest SNAPSHOT of "datanucleus-rdbms" and specify the persistence property "datanucleus.query.jdoql.navigationJoinTypeForFilter" as INNERJOIN (rather than the current default of working it out based on the NULLability of the field). This only applies to the FILTER of the query, so the SELECT clause will use the current default still. You can then run the TCK like that and see the effect. One I did see was a failure on org.apache.jdo.tck.query.jdoql.IfElseInFilter testPositive (which passes with current default join type strategy). This query has JDOQL of the form SELECT FROM org.apache.jdo.tck.pc.company.Employee WHERE (IF (this.manager == null) this.mentor.department.deptid ELSE this.manager.department.deptid) == this.department.deptid ORDER BY this.personid so likely the "IF THEN ELSE" expression in that example causing the difference. Anyone who wants to pursue this can look at the following classes The JDOQL query itself, look for method "compileQueryFull" https://github.com/datanucleus/datanucleus-rdbms/blob/master/src/main/java/org/datanucleus/store/rdbms/query/JDOQLQuery.java which then uses QueryToSQLMapper to convert the JDOQL compilation into an SQL query https://github.com/datanucleus/datanucleus-rdbms/blob/master/src/main/java/org/datanucleus/store/rdbms/query/QueryToSQLMapper.java And then kindly provide a Pull Request on GitHub that works for all situations. Regards -- Andy DataNucleus (Web: http://www.datanucleus.org Twitter: @datanucleus)
