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HHH-11793 - Change docs to point out that EAGER associations cannot be turn to LAZY with entity graphs

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Vlad Mihalcea 2017-06-08 08:53:17 +03:00
parent 2867e070ea
commit 6049131218
1 changed files with 8 additions and 2 deletions
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documentation/src/main/asciidoc/userguide/chapters/fetching/Fetching.adoc
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@ -204,8 +204,14 @@ include::{sourcedir}/GraphFetchingTest.java[tags=fetching-strategies-dynamic-fet
[NOTE]
====
Entity graphs are the way to override the EAGER fetching associations at runtime.
With JPQL, if an EAGER association is omitted, Hibernate will issue a secondary select for every association needed to be fetched eagerly.
Although the JPA standard specifies that you can override an EAGER fetching association at runtime using the `javax.persistence.fetchgraph` hint,
currently, Hibernate does not implement this feature, so EAGER associations cannot be fetched lazily.
For more info, check out the https://hibernate.atlassian.net/browse/HHH-8776[HHH-8776] Jira issue.
When executing a JPQL query, if an EAGER association is omitted, Hibernate will issue a secondary select for every association needed to be fetched eagerly,
which can lead dto N+1 query issues.
For this reason, it's better to use LAZY associations, and only fetch them eagerly on a per-query basis.
====
[[fetching-strategies-dynamic-fetching-entity-subgraph]]