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From Pinaki Poddar <>
Subject Re: Slice Error with simple query ( Websphere 7.0 & DB2 9.1 )
Date Fri, 27 Mar 2009 19:19:41 GMT

> Can't I use slice framework with databases which not have the same structure ?

Slice assumes that data is horizontally partitioned i.e. as if a huge table is sliced row-wise
and put into many separate databases. But this assumption is not a hard one. You can use Slice
even when the slices do not have the same schema but it will not be as seamless as in the
case of identical schemas. 

What Slice can not do is if slice-1 and slice-2 both contains table named 'T' but these two
tables have different structures. 

What Slice can do is
  1. slice-1: has table T1,T2
      slice-2: has Table T2,T3
      And T2 in slice1 and slice2 have identical schema.
   2. The Java entities C1, C2, C3 maps to T1,T2,T3 respectively

   3. Your application targets query as follows
             C1: to slice-1
             C2: no need to target it will execute in all slices 
             C3: to slice-2

    4. As Jody pointed out, the DistributedPolicy should be such that new C1,C3 instances
are stored *only* in slice-1 and slice-3 respectively.

Can't I use slice framework with databases which not have the same structure ?

I have two database with different information and I must to use all these information ...

How can I make query accross slices ? or accross the two database using openjpa ?

Thanks M. Poddar

  You can target the query that has Userdb1 to slice ONE only. 

   Slice, in general, considers that the schema in every slice is identical. 


I used Websphere 7.0 ( openjpa 1.2.1 snapshot ) and DB2 UBD 9.1

I want to configure slice describe as follow ( persistence.xml )

 <persistence-unit name="persistenceUnit">

                        <property name="openjpa.BrokerFactory" value="slice" />
                        <property name="openjpa.slice.Names"   value="ONE,TWO"/>
                        <property name="openjpa.slice.Master"  value="ONE"/>
                        <property name="openjpa.slice.Lenient" value="true"/>
                        <property name="openjpa.ConnectionDriverName" value=""
                        <property name="openjpa.ConnectionURL" value="jdbc:db2://localhost:52000/DB1"/>
                        <property name="openjpa.ConnectionUserName" value="db2admin"/>
                        <property name="openjpa.ConnectionPassword" value="db2admin,001"

                        <property name="openjpa.slice.ONE.ConnectionDriverName" value=""
                        <property name="openjpa.slice.ONE.ConnectionURL" value="jdbc:db2://localhost:52000/DB1"/>
                        <property name="openjpa.slice.ONE.ConnectionUserName" value="db2admin"/>
                        <property name="openjpa.slice.ONE.ConnectionPassword" value="db2admin,001"
                <property name="openjpa.slice.TWO.ConnectionDriverName" value=""
                <property name="openjpa.slice.TWO.ConnectionURL" value="jdbc:db2://localhost:52000/DB2"/>
                <property name="openjpa.slice.TWO.ConnectionUserName" value="db2admin"/>
                <property name="openjpa.slice.TWO.ConnectionPassword" value="db2admin,001"
                <property name="openjpa.slice.DistributionPolicy" value="org.apache.openjpa.slice.policy.MyUserDistributionPolicy"/>
                <property name="openjpa.Log" value="SQL=TRACE"/>

I want to use 2 several databases. For testing I build a simple database structure with one
table in each database. Each database is connected to a slice so, Userdb1 is in slice one
and Customerdb2 is in slice two.

When I try to make a simple SELECT udb1.udb1Id, udb1.udb1Name, udb1.udb1Mail FROM Userdb1
udb1, I have this error :  DB2 SQL error: SQLCODE: -204, SQLSTATE: 42704, ...

Slice want to find Userdb1 in slice TWO but this table is in slice ONE only...

How I can do solve this problem ?

Best regards :) 

Pinaki Poddar            
OpenJPA PMC Member/Committer
JPA Expert Group Member
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