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add a TIP about subqueries in filter conditions 

Signed-off-by: Gavin King <gavin@hibernate.org>
This commit is contained in:
Gavin King 2024-05-03 13:22:42 +02:00
parent 0cfb52d127
commit 927b046f13
1 changed files with 11 additions and 0 deletions
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11
documentation/src/main/asciidoc/introduction/Advanced.adoc
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@ -92,6 +92,17 @@ Note that the restriction specified by the `condition` or `defaultCondition` is
| `@Filter` | Specifies how a filter applies to a given entity or collection (many per filter)
|===
[TIP]
====
A filter `condition` may not specify joins to other tables, but it may contain a subquery.
[source,java]
----
@Filter(name="notDeleted"
condition="(select r.deletionTimestamp from Record r where r.id = record_id) is not null")
----
Only unqualified column names like `record_id` in this example are interpreted as belonging to the table of the filtered entity.
====
By default, a new session comes with every filter disabled.
A filter may be explicitly enabled in a given session by calling link:{doc-javadoc-url}org/hibernate/Session.html#enableFilter(java.lang.String)[`enableFilter()`] and assigning arguments to the parameters of the filter using the returned instance of link:{doc-javadoc-url}org/hibernate/Filter.html[`Filter`].
You should do this right at the _start_ of the session.