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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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10
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] [NOTE]
==== ====
Entity graphs are the way to override the EAGER fetching associations at runtime. Although the JPA standard specifies that you can override an EAGER fetching association at runtime using the `javax.persistence.fetchgraph` hint,
With JPQL, if an EAGER association is omitted, Hibernate will issue a secondary select for every association needed to be fetched eagerly. 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]] [[fetching-strategies-dynamic-fetching-entity-subgraph]]