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    <p>JPA's concept of inheritance is based on ordinary tables. It doesn't really "get" the idea of PostgreSQL's table inheritance. That's one of the costs of working with a spec designed to expose the lowest common denominator of features and do so portably.</p> <p>See <a href="http://java.dzone.com/articles/jpa-implementation-patterns-mapping" rel="noreferrer">this guide</a> for a decent summary of JPA inheritance strategies. Note that in the <a href="http://docs.oracle.com/javaee/6/api/javax/persistence/Inheritance.html" rel="noreferrer">newer Java 6 JavaDoc for @Inheritance</a> there is a note saying that:</p> <blockquote> <p>If the Inheritance annotation is not specified or if no inheritance type is specified for an entity class hierarchy, the SINGLE_TABLE mapping strategy is used.</p> </blockquote> <p>... and if you look at how <code>SINGLE_TABLE</code> works, it's not surprising it doesn't work for you; it's expecting all subclasses to be in one big table with a magic discriminator value.</p> <p><code>InheritanceType.TABLE_PER_CLASS</code> is closer to how Pg behaves, but I suspect that the JPA impl will get a bit confused when the base type tables have entries for each entity of a leaf type. It tries to do things like <code>UNION</code> queries across the subclass tables when querying on the superclass, and that could produce odd results - at least duplication if <code>UNION</code> is used and performance issues if it uses <code>UNION ALL</code>. Depending on exactly how the provider implements the strategy it may work at least partially. You'd have to test, and the results would possibly be fairly provider specific.</p> <p>A really good implementation of PG inheritance support for JPA would probably require JPA provider extensions for a new inheritance strategy that understood the PostgreSQL extensions for inheritance and for <code>ONLY</code> queries.</p> <p>If you can convince your JPA implementation to use <code>SELECT ... FROM ONLY subclass_table</code> when in <code>InheritanceType.TABLE_PER_CLASS</code> mode then it should inter-operate OK with PostgreSQL inheritance. It would see only the non-inherited rows in each table and work with them as if they were ordinary tables. Your other non-JPA code could then keep using the inheritance features. I guess it's possible you could modify the PostgreSQL dialect code for Hibernate to do this, but personally I wouldn't go there unless I absolutely <em>had</em> to make JPA support existing PostgreSQL schema that relied heavily on inheritance.</p>
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    1. COWell, saying that actually gave us a view of what we've tried to implement, so we decide to simplify the idea by restructuring the tables... Thanks anyway!
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