INNER JOIN Fetch query incorrectly generates LEFT join SQL
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Key: OPENJPA-547
URL: https://issues.apache.org/jira/browse/OPENJPA-547
Project: OpenJPA
Issue Type: Bug
Components: query
Reporter: Catalina Wei
Fix For: 1.0.3, 1.1.0
INNER JOIN FETCH should not generate SQL LEFT join.
Example:
lineitems (ToMany, FetchType=LAZY)
Order <===================================> OrderItem
order (ToOne, FetchType=LAZY)
For Query: select o from Order left join fetch o.lineitems
SQL generated
for DB2:
SELECT t0.oid, t0.version, t0.amount, t0.delivered, t1.ORDER_OID, t1.lid,
t1.version, t1.cost, t1.quantity
FROM TORDER t0 LEFT OUTER JOIN TORDERITEM t1 ON t0.oid = t1.ORDER_OID ORDER BY
t1.ORDER_OID ASC
for Oracle:
SELECT t0.oid, t0.version, t0.amount, t0.delivered, t1.ORDER_OID, t1.lid,
t1.version, t1.cost, t1.quantity FROM TORDER t0, TORDERITEM t1 WHERE t0.oid =
t1.ORDER_OID(+) ORDER BY t1.ORDER_OID ASC
The above SQL pushdown looked good.
However, if left join fetch is changed to inner join fetch:
select o from Order o inner join fetch o.lineitems
We are generating extra redundant LEFT joins:
for DB2:
SELECT t0.oid, t0.version, t0.amount, t0.delivered, t2.ORDER_OID, t2.lid,
t2.version, t2.cost, t2.quantity
FROM TORDER t0 INNER JOIN TORDERITEM t1 ON t0.oid = t1.ORDER_OID LEFT OUTER
JOIN TORDERITEM t2 ON t0.oid = t2.ORDER_OID ORDER BY t2.ORDER_OID ASC
for Oracle:
SELECT t0.oid, t0.version, t0.amount, t0.delivered, t2.ORDER_OID, t2.lid,
t2.version, t2.cost, t2.quantity FROM TORDER t0, TORDERITEM t1, TORDERITEM t2
WHERE t0.oid = t1.ORDER_OID AND t0.oid = t2.ORDER_OID(+) ORDER BY t2.ORDER_OID
ASC
Why do we generate the extra LEFT joins even for quereis explicitly requesting
INNER join fetch ?
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