JPA PagingItemReader with PostgreSQL - sql

Question

I have done a job that reads data from a db and writes it in a file. It works fine with an Oracle DB. However, when I use it with Postgres I get the following error:
org.postgresql.util.PSQLException: ERROR: subquery in FROM must have an alias
Hint: Por ejemplo, FROM (SELECT ...) [AS] foo.
Position: 15
Error Code: 0
The reader is defined as follows:
<bean id="myReader"
class="org.springframework.batch.item.database.Jpa PagingItemReader">
<property name="entityManagerFactory" ref="entityManagerFactory" />
<property name="queryString" value="select c from CountryEntity c" />
<property name="pageSize" value="1000"/>
</bean>
Does anybody know if this is a common issue related with Postgres? Do I need to use a specific configuration?

Answer 1

You need to configure your JPA provider to use the PostGreSQL dialect.
E.g. for Hibernate, you would use a setup (persistence.xml) like this:
<persistence-unit name="somename" transaction-type="RESOURCE_LOCAL">
<properties>
<property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect"/>
<property name="hibernate.connection.url" value="jdbc:postgresql:sample"/>
<property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver"/>
<property name="hibernate.format_sql" value="true"/>
<property name="hbm2ddl.auto" value="update"/>
</properties>
</persistence-unit>