OpenJPA doesn't generate SQL with efficient joins when joined inheritance
strategy is used and there is one-many relation in superclass
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Key: OPENJPA-717
URL: https://issues.apache.org/jira/browse/OPENJPA-717
Project: OpenJPA
Issue Type: Improvement
Components: query
Affects Versions: 1.2.0, 1.1.0, 1.0.3, 1.0.2, 1.0.1, 1.0.0
Reporter: Xiaoqin Feng
The test case has a subclass that extends an abstract superclass that
basically contains a single additional field 'S1', a one-to-one relation
'superOne' and a one-to-many relation 'superMany'. The superclass has an
inheritance strategy of 'JOINED'.
When executing the query:
SELECT s FROM Subclass s WHERE s.a1 = :a1
three SQL statements get generated:
SELECT t1.ID, t0.id, t1.S1, t2.ID, t2.S1, t0.A1, t3.ID, t3.A1
FROM SUBCLASS t0, SUPERCLASS t1, SUPERCLASSONE t2, SUBCLASSONE t3
WHERE (t0.A1 = ?) AND t0.SUBCLASSONE_ID = t3.ID(+) AND t0.id = t1.ID AND
t1.SUPERCLASSONE_ID = t2.ID(+)
SELECT t0.id, t1.ID, t1.A1
FROM SUBCLASS t0, SUBCLASSMANY t1
WHERE (t0.A1 = ?) AND t0.id = t1.SUBCLASS_ID ORDER BY t0.id ASC
SELECT t1.ID, t2.ID, t2.S1
FROM SUBCLASS t0, SUPERCLASS t1, SUPERCLASSMANY t2
WHERE (t0.A1 = ?) AND t1.ID = t2.SUPERCLASS_ID ORDER BY t1.ID ASC
The third one doesn't contain the condition t0.ID = t1.ID
Although final returned result set is correct because of the logical union, the
third SQL returns more rows so it has bad performance.
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