25.6. Fetching

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Fetching too much data is the number one performance issue for the vast majority of JPA applications.

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Hibernate supports both entity queries (JPQL/HQL and Criteria API) and native SQL statements.
Entity queries are useful only if you need to modify the fetched entities, therefore benefiting from the automatic dirty checking mechanism.

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For read-only transactions, you should fetch DTO projections because they allow you to select just as many columns as you need to fulfill a certain business use case.
This has many benefits like reducing the load on the currently running Persistence Context because DTO projections don&#8217;t need to be managed.

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