cannot simultaneously fetch multiple bags
November 25, 2014
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ref from http://stackoverflow.com/questions/17566304/multiple-fetches-with-eager-type-in-hibernate-with-jpa
The root cause of the problem is that when Hibernate fetches SQL query results there is no simple way to tell which child element belongs to which collection. See this blog entry for more detailed explanation with an example. To summarize you have following workarounds:
- Load each collection separately using subselect
- Force usage of list instead of bag by adding index column
- Use unordered collection like Set.