In-memory query evaluation : support correlated subqueries

[andyjefferson]

See JDO2 TCK tests

CorrelatedSubqueries.testPositive CorrelatedSubqueriesWithParameters.testPositive

query: SELECT FROM org.apache.jdo.tck.pc.company.Employee WHERE this.weeklyhours > (SELECT AVG(e.weeklyhours) FROM this.department.employees e) [java] expected: java.util.ArrayList of size 6 [java] [FullTimeEmployee(1, emp1Last, emp1First, born 10/Jun/1970, phone {}, hired 1/Jan/1999, weeklyhours 40.0, $30000.0), FullTimeEmployee(2, emp2Last, emp2First, born 22/Dec/1975, phone {}, hired 1/Jul/2003, weeklyhours 40.0, $20000.0), FullTimeEmployee(4, emp4Last, emp4First, born 6/Sep/1973, phone {}, hired 15/Apr/2001, weeklyhours 40.0, $25000.0), FullTimeEmployee(6, emp6Last, emp6First, born 10/Jun/1969, phone {}, hired 1/Jun/2002, weeklyhours 40.0, $22000.0), FullTimeEmployee(7, emp7Last, emp7First, born 10/Jun/1970, phone {}, hired 1/Jan/2000, weeklyhours 40.0, $40000.0), FullTimeEmployee(10, emp10Last, emp10First, born 5/Sep/1972, phone {}, hired 1/Oct/2002, weeklyhours 40.0, $24000.0)] [java] got: java.util.ArrayList of size 7 [java] [FullTimeEmployee(1, emp1Last, emp1First, born 10/Jun/1970, phone {}, hired 1/Jan/1999, weeklyhours 40.0, $30000.0), FullTimeEmployee(2, emp2Last, emp2First, born 22/Dec/1975, phone {}, hired 1/Jul/2003, weeklyhours 40.0, $20000.0), FullTimeEmployee(7, emp7Last, emp7First, born 10/Jun/1970, phone {}, hired 1/Jan/2000, weeklyhours 40.0, $40000.0), FullTimeEmployee(10, emp10Last, emp10First, born 5/Sep/1972, phone {}, hired 1/Oct/2002, weeklyhours 40.0, $24000.0), FullTimeEmployee(4, emp4Last, emp4First, born 6/Sep/1973, phone {}, hired 15/Apr/2001, weeklyhours 40.0, $25000.0), PartTimeEmployee(5, emp5Last, emp5First, born 5/Jul/1962, phone {}, hired 1/Nov/2002, weeklyhours 35.0, $18000.0), FullTimeEmployee(6, emp6Last, emp6First, born 10/Jun/1969, phone {}, hired 1/Jun/2002, weeklyhours 40.0, $22000.0)] [java] at org.apache.jdo.tck.JDO_Test.fail(JDO_Test.java:682) [java] at org.apache.jdo.tck.query.QueryTest.queryFailed(QueryTest.java:518) [java] at org.apache.jdo.tck.query.QueryTest.checkQueryResultWithoutOrder(QueryTest.java:548) [java] at org.apache.jdo.tck.query.QueryTest.execute(QueryTest.java:1293) [java] at org.apache.jdo.tck.query.QueryTest.executeJDOQuery(QueryTest.java:1161) [java] at org.apache.jdo.tck.query.jdoql.subqueries.CorrelatedSubqueries.testPositive(CorrelatedSubqueries.java:83)

A problem is that the candidates of the subquery will need retrieval and input before evaluation.

• If the candidates of the subquery are of a different class to the candidate of the outer query then we need to retrieve them first.
• If the candidates of the subquery relate to the outer query then this isn't necessary and we can nest the subquery evaluation in the outer query evaluation.