[eclipselink-users] How to force a query to use default(write) connectio

[Kohei Nozaki <kohei.nozaki@xxxxxxxxxx>]

Hello,

I'm looking for a way to force a query to use default(write) connection  
pool.

Let's say we have following properties in persistence.xml:

...
<property name="javax.persistence.jdbc.driver"  
value="org.apache.derby.jdbc.EmbeddedDriver"/>
<property name="javax.persistence.jdbc.url"  
value="jdbc:derby:memory:masterDB;create=true"/>
<property name="eclipselink.connection-pool.read.url"  
value="jdbc:derby:memory:slaveDB;create=true" />
...

This makes read queries to be executed in "slaveDB" but I need to  
forcibly execute some read queries on "masterDB" to avoid replication  
lag (I use a MySQL cluster for my real usecase).

What's the best way to achieve this requirement? it would be great if  
there is a query hint to set the destination of a query to "master"  
forcibly, something like this:

  String mycol = em.createQuery("select m from MyTable m", MyTable.class)
    .setHint("eclipselink.forceMaster", true) // this hint does not exist
    .getSingleResult().getMycol();

(taken from
https://github.com/lbtc-xxx/eclipselink-force-write/blob/master/src/test/java/main/ConnectionDestinationTest.java#L68-L75  
)

I have found a solution which is beginning a transaction then issue a  
native query (e.g. SELECT 1 FROM SYSIBM.SYSDUMMY1) finally issue a JPQL  
query, but looks kludgy.

(complete testcase:
https://github.com/lbtc-xxx/eclipselink-force-write/blob/master/src/test/java/main/ConnectionDestinationTest.java#L111-L120  
)

Thanks,
Kohei