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HHH-16931 document getResultCount()

This commit is contained in:
Gavin King 2024-02-19 22:55:22 +01:00
parent a562ab2462
commit 9bb15727e4
1 changed files with 20 additions and 7 deletions
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27
documentation/src/main/asciidoc/introduction/Interacting.adoc
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@ -838,7 +838,7 @@ So if there are any unflushed changes to ``Book``s, this query might return stal
[source,java]
----
List<Book> books =
session.createNativeQuery("select * from Books")
session.createNativeQuery("select * from Books", Book.class)
.getResultList()
----
@ -849,7 +849,7 @@ Either, we could simply force a flush by calling `flush()` or by setting the flu
[source,java]
----
List<Book> books =
session.createNativeQuery("select * from Books")
session.createNativeQuery("select * from Books", Book.class)
.setHibernateFlushMode(ALWAYS)
.getResultList()
----
@ -859,7 +859,7 @@ Or, alternatively, we could tell Hibernate which modified state affects the resu
[source,java]
----
List<Book> books =
session.createNativeQuery("select * from Books")
session.createNativeQuery("select * from Books", Book.class)
.addSynchronizedEntityClass(Book.class)
.getResultList()
----
@ -893,7 +893,7 @@ For example, this:
[source,java]
----
List<Book> books =
session.createSelectionQuery("from Book where title like ?1 order by title")
session.createSelectionQuery("from Book where title like ?1 order by title", Book.class)
.setParameter(1, titlePattern)
.setMaxResults(MAX_RESULTS)
.getResultList();
@ -903,8 +903,9 @@ is simpler than:
[source,java]
----
// a worse way to do pagination
List<Book> books =
session.createSelectionQuery("from Book where title like ?1 order by title fetch first ?2 rows only")
session.createSelectionQuery("from Book where title like ?1 order by title fetch first ?2 rows only", Book.class)
.setParameter(1, titlePattern)
.setParameter(2, MAX_RESULTS)
.getResultList();
@ -915,12 +916,23 @@ Hibernate's `SelectionQuery` has a slightly different way to paginate the query
[source,java]
----
List<Book> books =
session.createSelectionQuery("from Book where title like ?1 order by title")
session.createSelectionQuery("from Book where title like ?1 order by title", Book.class)
.setParameter(1, titlePattern)
.setPage(Page.first(MAX_RESULTS))
.getResultList();
----
The `getResultCount()` method is useful for displaying the number of pages of results:
[source,java]
----
SelectionQuery<Book> query =
session.createSelectionQuery("from Book where title like ?1 order by title", Book.class)
.setParameter(1, titlePattern);
long pages = query.getResultCount() / MAX_RESULTS;
List<Book> books = query.setMaxResults(MAX_RESULTS).getResultList();
----
A closely-related issue is ordering.
It's quite common for pagination to be combined with the need to order query results by a field that's determined at runtime.
So, as an alternative to the HQL `order by` clause, `SelectionQuery` offers the ability to specify that the query results should be ordered by one or more fields of the entity type returned by the query:
@ -928,7 +940,7 @@ So, as an alternative to the HQL `order by` clause, `SelectionQuery` offers the
[source,java]
----
List<Book> books =
session.createSelectionQuery("from Book where title like ?1")
session.createSelectionQuery("from Book where title like ?1", Book.class)
.setParameter(1, titlePattern)
.setOrder(List.of(Order.asc(Book._title), Order.asc(Book._isbn)))
.setMaxResults(MAX_RESULTS)
@ -946,6 +958,7 @@ Unfortunately, there's no way to do this using JPA's `TypedQuery` interface.
| `setFirstResult()` | Set an offset on the results returned by a query | &#10004;
| `setPage()` | Set the limit and offset by specifying a `Page` object | &#10006;
| `setOrder()` | Specify how the query results should be ordered | &#10006;
| `getResultCount()` | Determine how many results the query would return in the absence of any limit or offset | &#10006;
|===
[[projection-lists]]