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From "John Stecher (JIRA)" <j...@apache.org>
Subject [jira] Commented: (OPENJPA-134) Extra unneeded SQL joins for OneToMany relationship with fetch type EAGER
Date Mon, 26 Feb 2007 22:45:05 GMT

    [ https://issues.apache.org/jira/browse/OPENJPA-134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12476027
] 

John Stecher commented on OPENJPA-134:
--------------------------------------

Just curious if there has been any movement on this JIRA.  This problem actually presents
itself in the test bucket that IBM has been running trying to work through the performance
issues of OpenJPA and puts the OpenJPA runtime behind the competitive implementations in the
scenarios above.  I am interested in getting some feedback from those that understand the
code a little more about this bug and getting a possible fix generated for it.  

In my mind there is no reason that the the Orderlines->Orders Eager,Eager relationship
should ever issues a 2 join query.  It should be a single left outer join with the eager back
pointer filled by the initial orderline query.

Thoughts?


> Extra unneeded SQL joins for OneToMany relationship with fetch type EAGER
> -------------------------------------------------------------------------
>
>                 Key: OPENJPA-134
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-134
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: sql
>            Reporter: Catalina Wei
>
> Running JPAConfiguration default setting for EagerFetchMode (FetchModeValue.EAGER_PARALLEL),

> the SQL generated is sub-optimal.
> Consider the following entities:
>                                      lineitems( OneToMany ) 
>             Order  <===========================> OrderItem
>                                     order ( ManyToOne )
> Case 1:  why not combining 2 SQL to 1 SQL ?
> =================================================================================================
> Order.lineitmes(EAGER):
> OrderItem.order(LAZY):
> Executing query: select o from Order o
> 2173  demo  TRACE  [main] openjpa.jdbc.SQL - <t 1094730048, conn 1318342292> executing
prepstmnt 1299336562 
> SELECT t0.oid, t0.version, t0.amount, t0.customer_countryCode, t0.customer_id, t0.delivered,
t0.shipaddr FROM Order t0
> 2213  demo  TRACE  [main] openjpa.jdbc.SQL - <t 1094730048, conn 1318342292> [40
ms] spent
> 2223  demo  TRACE  [main] openjpa.jdbc.SQL - <t 1094730048, conn 1318342292> executing
prepstmnt 1406424020 
> SELECT t0.oid, t1.lid, t1.version, t1.cost, t1.order_oid, t1.part_partno, t1.quantity
FROM Order t0 INNER JOIN OrderItem t1 ON t0.oid = t1.order_oid ORDER BY t0.oid ASC
> Case 2: extra unneeded LEFT OUTER JOIN,  if eliminated, the selection aliase t2 should
change to t1:
> =============================================================================================
> Order.lineitmes(EAGER):
> OrderItem.order(LAZY):
> Executing query: select o from Order o left join fetch o.lineitems
> 2403  demo  TRACE  [main] openjpa.jdbc.SQL - <t 1094730048, conn 1314410072> executing
prepstmnt 1500797300 
> SELECT t0.oid, t0.version, t0.amount, t0.customer_countryCode, t0.customer_id, t0.delivered,
t0.shipaddr, t2.order_oid, t2.lid, t2.version, t2.cost, t2.part_partno, t2.quantity FROM Order
t0 LEFT OUTER JOIN OrderItem t1 ON t0.oid = t1.order_oid LEFT OUTER JOIN OrderItem t2 ON t0.oid
= t2.order_oid ORDER BY t2.order_oid ASC
> Case  3: why not generating 1 SQL ?
> ==================================================================================================
> Order.lineitmes(EAGER):
> OrderItem.order(EAGER):
> Executing query: select o from Order o
> 2343  demo  TRACE  [main] openjpa.jdbc.SQL - <t 1094730048, conn 1318342292> executing
prepstmnt 384833264 SELECT t0.oid, t0.version, t0.amount, t0.customer_countryCode, t0.customer_id,
t0.delivered, t0.shipaddr FROM Order t0
> 2383  demo  TRACE  [main] openjpa.jdbc.SQL - <t 1094730048, conn 1318342292> [40
ms] spent
> 2393  demo  TRACE  [main] openjpa.jdbc.SQL - <t 1094730048, conn 1318342292> executing
prepstmnt 1722705582 
> SELECT t0.oid, t1.lid, t1.version, t1.cost, t2.oid, t2.version, t2.amount, t2.customer_countryCode,
t2.customer_id, t2.delivered, t2.shipaddr, t1.part_partno, t1.quantity FROM Order t0 INNER
JOIN OrderItem t1 ON t0.oid = t1.order_oid LEFT OUTER JOIN Order t2 ON t1.order_oid = t2.oid
ORDER BY t0.oid ASC
> 2393  demo  TRACE  [main] openjpa.jdbc.SQL - <t 1094730048, conn 1318342292> [0
ms] spent
> 3134  demo  TRACE  [main] openjpa.jdbc.SQL - <t 1094730048, conn 1318342292> executing
prepstmnt 950548648 
> SELECT t0.lid, t0.version, t0.cost, t1.oid, t1.version, t1.amount, t1.customer_countryCode,
t1.customer_id, t1.delivered, t1.shipaddr, t0.part_partno, t0.quantity FROM OrderItem t0 LEFT
OUTER JOIN Order t1 ON t0.order_oid = t1.oid WHERE t0.order_oid = ? [params=(int) 88]
> 3134  demo  TRACE  [main] openjpa.jdbc.SQL - <t 1094730048, conn 1318342292> [0
ms] spent
> Case 4:  duplicate selections and redundant joins
> ==================================================================================================
> Order.lineitmes(EAGER):
> OrderItem.order(EAGER):
> Executing query: select o from Order o left join fetch o.lineitems
> 2273  demo  TRACE  [main] openjpa.jdbc.SQL - <t 1094730048, conn 1307463150> executing
prepstmnt 1565154634 
> SELECT t0.oid, t0.version, t0.amount, t0.customer_countryCode, t0.customer_id, t0.delivered,
t0.shipaddr, t2.order_oid, t2.lid, t2.version, t2.cost, t3.oid, t3.version, t3.amount, t3.customer_countryCode,
t3.customer_id, t3.delivered, t3.shipaddr, t2.part_partno, t2.quantity FROM Order t0 LEFT
OUTER JOIN OrderItem t1 ON t0.oid = t1.order_oid LEFT OUTER JOIN OrderItem t2 ON t0.oid =
t2.order_oid LEFT OUTER JOIN Order t3 ON t2.order_oid = t3.oid ORDER BY t2.order_oid ASC

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