blocks|key|218561|text|出现此警告的原因是，当使用fetch+join时，结果集中的order仅按所选实体的ID定义(而不是按join+fetched)定义。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|218562|如果内存中的这种排序导致了问题，请不要将firsResult/maxResults用于JOIN+FETCH。|218563|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Reason for this warning is that when fetch join is used, order in result sets is defined only by ID of selected entity (and not by join fetched).

If this sorting in memory is causing problems, do not use firsResult/maxResults with JOIN FETCH.

blocks|key|221609|text|要避免此警告，必须将call+getSingleResult更改为getResultList().get(0)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|221610|entityMap^0|F|F|X|M|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

To avoid this WARNING you have to change the call <code>getSingleResult</code> to 
<code>getResultList().get(0)</code>

blocks|key|3085462|text|问题是你会得到笛卡尔乘积进行连接。偏移量将剪切您的记录集，而不会查看您是否仍在同一根标识类上|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3085463|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

the problem is you will get cartesian product doing JOIN. The offset will cut your recordset without looking if you are still on same root identity class

blocks|key|218622|text|我猜emp有许多部门，这是一对多的关系。Hibernate将使用获取的部门记录为该查询提取许多行。因此，只有在将结果真正提取到内存中时，才能决定结果集的顺序。因此，分页将在内存中完成。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|218623|如果您不想使用emp获取部门，但仍然希望根据部门进行一些查询，则可以在没有警告的情况下获得结果(不需要在内存中进行排序)。为此，您必须删除"fetch“子句。因此，类似于以下内容：|218624|emp.salary+=+"from+employee+as+emp+left+join+sal+left+join+emp.department+dep+where+emp.id+=+:id+emp.salary+dep.name+=+'testing‘and+sal.salary+>+5000“|218625|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

I guess the emp has many departments which is a One to Many relationship. Hibernate will fetch many rows for this query with fetched department records. So the order of result set can not be decided until it has really fetch the results to the memory. So the pagination will be done in memory.

If you do not want to fetch the departments with emp, but still want to do some query based on the department, you can achieve the result with out warning (without doing ordering in the memory). For that simply you have to remove the "fetch" clause. So something like as follows:

QUERY = "from employee as emp left join emp.salary sal left join emp.department dep where emp.id = :id and dep.name = 'testing' and sal.salary > 5000 "

blocks|key|218650|text|尽管您获得了有效的结果，但SQL查询会获取所有数据，并且效率并不像它应该的那样高。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|218651|因此，您有两个选择。|218652|修复了可以以读写模式获取实体的两个SQL查询的问题|218653|解决此问题的最简单方法是执行两个查询：|218654|。第一个查询将获取与所提供的过滤条件匹配的根实体标识符。。第二个查询将使用先前提取的根实体标识符来获取父实体和子实体。|218655|这种方法非常容易实现，如下所示：|218656|List<Long>+postIds+=+entityManager
.createQuery(
++++"select+p.id+"+%2B
++++"from+Post+p+"+%2B
++++"where+p.title+like+:titlePattern+"+%2B
++++"order+by+p.createdOn",+Long.class)
.setParameter(
++++"titlePattern",
++++"High-Performance+Java+Persistence+%25"
)
.setMaxResults(5)
.getResultList();
+
List<Post>+posts+=+entityManager
.createQuery(
++++"select+distinct+p+"+%2B
++++"from+Post+p+"+%2B
++++"left+join+fetch+p.comments+"+%2B
++++"where+p.id+in+(:postIds)+"++%2B
++++"order+by+p.createdOn",+Post.class)
.setParameter("postIds",+postIds)
.setHint(
++++"hibernate.query.passDistinctThrough",+
++++false
)
.getResultList();|code-block|syntax|javascript|218657|修复一个只能在只读模式下获取实体的SQL查询的问题|218658|第二种方法是对符合过滤条件的父实体和子实体的结果集使用SDENSE_RANK，并仅限制前N个post条目的输出。|218659|SQL查询可能如下所示：|218660|@NamedNativeQuery(
++++name+=+"PostWithCommentByRank",
++++query+=
++++++++"SELECT+*+"+%2B
++++++++"FROM+(+++"+%2B
++++++++"++++SELECT+*,+dense_rank()+OVER+(ORDER+BY+\"p.created_on\",+\"p.id\")+rank+"+%2B
++++++++"++++FROM+(+++"+%2B
++++++++"++++++++SELECT+p.id+AS+\"p.id\",+"+%2B
++++++++"+++++++++++++++p.created_on+AS+\"p.created_on\",+"+%2B
++++++++"+++++++++++++++p.title+AS+\"p.title\",+"+%2B
++++++++"+++++++++++++++pc.id+as+\"pc.id\",+"+%2B
++++++++"+++++++++++++++pc.created_on+AS+\"pc.created_on\",+"+%2B
++++++++"+++++++++++++++pc.review+AS+\"pc.review\",+"+%2B
++++++++"+++++++++++++++pc.post_id+AS+\"pc.post_id\"+"+%2B
++++++++"++++++++FROM+post+p++"+%2B
++++++++"++++++++LEFT+JOIN+post_comment+pc+ON+p.id+=+pc.post_id+"+%2B
++++++++"++++++++WHERE+p.title+LIKE+:titlePattern+"+%2B
++++++++"++++++++ORDER+BY+p.created_on+"+%2B
++++++++"++++)+p_pc+"+%2B
++++++++")+p_pc_r+"+%2B
++++++++"WHERE+p_pc_r.rank+<=+:rank+",
++++resultSetMapping+=+"PostWithCommentByRankMapping"
)
@SqlResultSetMapping(
++++name+=+"PostWithCommentByRankMapping",
++++entities+=+{
++++++++@EntityResult(
++++++++++++entityClass+=+Post.class,
++++++++++++fields+=+{
++++++++++++++++@FieldResult(name+=+"id",+column+=+"p.id"),
++++++++++++++++@FieldResult(name+=+"createdOn",+column+=+"p.created_on"),
++++++++++++++++@FieldResult(name+=+"title",+column+=+"p.title"),
++++++++++++}
++++++++),
++++++++@EntityResult(
++++++++++++entityClass+=+PostComment.class,
++++++++++++fields+=+{
++++++++++++++++@FieldResult(name+=+"id",+column+=+"pc.id"),
++++++++++++++++@FieldResult(name+=+"createdOn",+column+=+"pc.created_on"),
++++++++++++++++@FieldResult(name+=+"review",+column+=+"pc.review"),
++++++++++++++++@FieldResult(name+=+"post",+column+=+"pc.post_id"),
++++++++++++}
++++++++)
++++}
)|218661|@NamedNativeQuery获取与所提供的标题匹配的所有Post实体及其关联的PostComment子实体。DENSE_RANK窗口函数用于为每个Post和PostComment连接记录分配排名，以便我们以后可以只过滤我们感兴趣的Post记录的数量。|offset|length|style|CODE|218662|SqlResultSetMapping提供了SQL级列别名和需要填充的JPA实体属性之间的映射。|218663|现在，我们可以像这样执行PostWithCommentByRank+@NamedNativeQuery：|218664|List<Post>+posts+=+entityManager
.createNamedQuery("PostWithCommentByRank")
.setParameter(
++++"titlePattern",
++++"High-Performance+Java+Persistence+%25"
)
.setParameter(
++++"rank",
++++5
)
.unwrap(NativeQuery.class)
.setResultTransformer(
++++new+DistinctPostResultTransformer(entityManager)
)
.getResultList();|218665|现在，在缺省情况下，像PostWithCommentByRank查询这样的原生SQL查询将获取同一JDBC行中的Post和PostComment，因此我们最终将得到一个包含这两个实体的Object[]。|218666|但是，我们希望将表格Object[]数组转换为父子实体树，因此，我们需要使用Hibernate+ResultTransformer。|218667|DistinctPostResultTransformer如下所示：|218668|public+class+DistinctPostResultTransformer
++++++++extends+BasicTransformerAdapter+{
+
++++private+final+EntityManager+entityManager;
+
++++public+DistinctPostResultTransformer(
++++++++++++EntityManager+entityManager)+{
++++++++this.entityManager+=+entityManager;
++++}
+
++++@Override
++++public+List+transformList(
++++++++++++List+list)+{
+++++++++++++
++++++++Map<Serializable,+Identifiable>+identifiableMap+=
++++++++++++new+LinkedHashMap<>(list.size());
+++++++++++++
++++++++for+(Object+entityArray+:+list)+{
++++++++++++if+(Object[].class.isAssignableFrom(entityArray.getClass()))+{
++++++++++++++++Post+post+=+null;
++++++++++++++++PostComment+comment+=+null;
+
++++++++++++++++Object[]+tuples+=+(Object[])+entityArray;
+
++++++++++++++++for+(Object+tuple+:+tuples)+{
++++++++++++++++++++if(tuple+instanceof+Identifiable)+{
++++++++++++++++++++++++entityManager.detach(tuple);
+
++++++++++++++++++++++++if+(tuple+instanceof+Post)+{
++++++++++++++++++++++++++++post+=+(Post)+tuple;
++++++++++++++++++++++++}
++++++++++++++++++++++++else+if+(tuple+instanceof+PostComment)+{
++++++++++++++++++++++++++++comment+=+(PostComment)+tuple;
++++++++++++++++++++++++}
++++++++++++++++++++++++else+{
++++++++++++++++++++++++++++throw+new+UnsupportedOperationException(
++++++++++++++++++++++++++++++++"Tuple+"+%2B+tuple.getClass()+%2B+"+is+not+supported!"
++++++++++++++++++++++++++++);
++++++++++++++++++++++++}
++++++++++++++++++++}
++++++++++++++++}
+
++++++++++++++++if+(post+!=+null)+{
++++++++++++++++++++if+(!identifiableMap.containsKey(post.getId()))+{
++++++++++++++++++++++++identifiableMap.put(post.getId(),+post);
++++++++++++++++++++++++post.setComments(new+ArrayList<>());
++++++++++++++++++++}
++++++++++++++++++++if+(comment+!=+null)+{
++++++++++++++++++++++++post.addComment(comment);
++++++++++++++++++++}
++++++++++++++++}
++++++++++++}
++++++++}
++++++++return+new+ArrayList<>(identifiableMap.values());
++++}
}|218669|DistinctPostResultTransformer必须分离正在获取的实体，因为我们正在重写子集合，而我们不希望将其作为实体状态转换传播：|218670|post.setComments(new+ArrayList<>());|218671|entityMap|0|LINK|mutability|MUTABLE|url|https://vladmihalcea.com/why-you-should-use-the-hibernate-resulttransformer-to-customize-result-set-mappings/|1|https://vladmihalcea.com/fix-hibernate-hhh000104-entity-fetch-pagination-warning-message/^0|0|0|0|0|0|0|0|0|0|0|0|0|H|16|B|1L|A|29|B|0|0|J|0|C|L|Y|H|0|0|B|L|1P|B|2K|8|0|A|8|1C|H|1C|H|0|0|0|T|0|0|0|T|0|T|1|0|0^^$0|@$1|2|3|4|5|6|7|1W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1X|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|1Y|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|20|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|21|8|@]|9|@]|A|$]]|$1|L|3|M|5|N|7|22|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|23|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|24|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|25|8|@]|9|@]|A|$]]|$1|W|3|X|5|N|7|26|8|@]|9|@]|A|$O|P]]|$1|Y|3|Z|5|6|7|27|8|@$10|28|11|29|12|13]|$10|2A|11|2B|12|13]|$10|2C|11|2D|12|13]|$10|2E|11|2F|12|13]]|9|@]|A|$]]|$1|14|3|15|5|6|7|2G|8|@$10|2H|11|2I|12|13]]|9|@]|A|$]]|$1|16|3|17|5|6|7|2J|8|@$10|2K|11|2L|12|13]|$10|2M|11|2N|12|13]]|9|@]|A|$]]|$1|18|3|19|5|N|7|2O|8|@]|9|@]|A|$O|P]]|$1|1A|3|1B|5|6|7|2P|8|@$10|2Q|11|2R|12|13]|$10|2S|11|2T|12|13]|$10|2U|11|2V|12|13]]|9|@]|A|$]]|$1|1C|3|1D|5|6|7|2W|8|@$10|2X|11|2Y|12|13]|$10|2Z|11|30|12|13]]|9|@$10|31|11|32|1|33]]|A|$]]|$1|1E|3|1F|5|6|7|34|8|@$10|35|11|36|12|13]]|9|@]|A|$]]|$1|1G|3|1H|5|N|7|37|8|@]|9|@]|A|$O|P]]|$1|1I|3|1J|5|6|7|38|8|@$10|39|11|3A|12|13]]|9|@$10|3B|11|3C|1|3D]]|A|$]]|$1|1K|3|1L|5|N|7|3E|8|@]|9|@]|A|$O|P]]|$1|1M|3|-4|5|6|7|3F|8|@]|9|@]|A|$]]]|1N|$1O|$5|1P|1Q|1R|A|$1S|1T]]|1U|$5|1P|1Q|1R|A|$1S|1V]]]]

Although you are getting valid results, the SQL query fetches all data and it's not as efficient as it should.
So, you have two options.
<h2>Fixing the issue with two SQL queries that can fetch entities in read-write mode</h2>
The easiest way to fix this issue is to execute two queries:
. The first query will fetch the root entity identifiers matching the provided filtering criteria.
. The second query will use the previously extracted root entity identifiers to fetch the parent and the child entities.
This approach is very easy to implement and looks as follows:
<pre><code>List&lt;Long&gt; postIds = entityManager
.createQuery(
 &quot;select p.id &quot; +
 &quot;from Post p &quot; +
 &quot;where p.title like :titlePattern &quot; +
 &quot;order by p.createdOn&quot;, Long.class)
.setParameter(
 &quot;titlePattern&quot;,
 &quot;High-Performance Java Persistence %&quot;
)
.setMaxResults(5)
.getResultList();
 
List&lt;Post&gt; posts = entityManager
.createQuery(
 &quot;select distinct p &quot; +
 &quot;from Post p &quot; +
 &quot;left join fetch p.comments &quot; +
 &quot;where p.id in (:postIds) &quot; +
 &quot;order by p.createdOn&quot;, Post.class)
.setParameter(&quot;postIds&quot;, postIds)
.setHint(
 &quot;hibernate.query.passDistinctThrough&quot;, 
 false
)
.getResultList();
</code></pre>
<h2>Fixing the issue with one SQL query that can only fetch entities in read-only mode</h2>
The second approach is to use SDENSE_RANK over the result set of parent and child entities that match our filtering criteria and restrict the output for the first N post entries only.
The SQL query can look as follows:
<pre><code>@NamedNativeQuery(
 name = &quot;PostWithCommentByRank&quot;,
 query =
 &quot;SELECT * &quot; +
 &quot;FROM ( &quot; +
 &quot; SELECT *, dense_rank() OVER (ORDER BY \&quot;p.created_on\&quot;, \&quot;p.id\&quot;) rank &quot; +
 &quot; FROM ( &quot; +
 &quot; SELECT p.id AS \&quot;p.id\&quot;, &quot; +
 &quot; p.created_on AS \&quot;p.created_on\&quot;, &quot; +
 &quot; p.title AS \&quot;p.title\&quot;, &quot; +
 &quot; pc.id as \&quot;pc.id\&quot;, &quot; +
 &quot; pc.created_on AS \&quot;pc.created_on\&quot;, &quot; +
 &quot; pc.review AS \&quot;pc.review\&quot;, &quot; +
 &quot; pc.post_id AS \&quot;pc.post_id\&quot; &quot; +
 &quot; FROM post p &quot; +
 &quot; LEFT JOIN post_comment pc ON p.id = pc.post_id &quot; +
 &quot; WHERE p.title LIKE :titlePattern &quot; +
 &quot; ORDER BY p.created_on &quot; +
 &quot; ) p_pc &quot; +
 &quot;) p_pc_r &quot; +
 &quot;WHERE p_pc_r.rank &lt;= :rank &quot;,
 resultSetMapping = &quot;PostWithCommentByRankMapping&quot;
)
@SqlResultSetMapping(
 name = &quot;PostWithCommentByRankMapping&quot;,
 entities = {
 @EntityResult(
 entityClass = Post.class,
 fields = {
 @FieldResult(name = &quot;id&quot;, column = &quot;p.id&quot;),
 @FieldResult(name = &quot;createdOn&quot;, column = &quot;p.created_on&quot;),
 @FieldResult(name = &quot;title&quot;, column = &quot;p.title&quot;),
 }
 ),
 @EntityResult(
 entityClass = PostComment.class,
 fields = {
 @FieldResult(name = &quot;id&quot;, column = &quot;pc.id&quot;),
 @FieldResult(name = &quot;createdOn&quot;, column = &quot;pc.created_on&quot;),
 @FieldResult(name = &quot;review&quot;, column = &quot;pc.review&quot;),
 @FieldResult(name = &quot;post&quot;, column = &quot;pc.post_id&quot;),
 }
 )
 }
)
</code></pre>
The <code>@NamedNativeQuery</code> fetches all Post entities matching the provided title along with their associated <code>PostComment</code> child entities. The <code>DENSE_RANK</code> Window Function is used to assign the rank for each Post and <code>PostComment</code> joined record so that we can later filter just the amount of Post records we are interested in fetching.
The <code>SqlResultSetMapping</code> provides the mapping between the SQL-level column aliases and the JPA entity properties that need to be populated.
Now, we can execute the <code>PostWithCommentByRank</code> <code>@NamedNativeQuery</code> like this:
<pre><code>List&lt;Post&gt; posts = entityManager
.createNamedQuery(&quot;PostWithCommentByRank&quot;)
.setParameter(
 &quot;titlePattern&quot;,
 &quot;High-Performance Java Persistence %&quot;
)
.setParameter(
 &quot;rank&quot;,
 5
)
.unwrap(NativeQuery.class)
.setResultTransformer(
 new DistinctPostResultTransformer(entityManager)
)
.getResultList();
</code></pre>
Now, by default, a native SQL query like the <code>PostWithCommentByRank</code> one would fetch the Post and the <code>PostComment</code> in the same JDBC row, so we will end up with an <code>Object[]</code> containing both entities.
However, we want to transform the tabular <code>Object[]</code> array into a tree of parent-child entities, and for this reason, we need to use the Hibernate <a href="https://vladmihalcea.com/why-you-should-use-the-hibernate-resulttransformer-to-customize-result-set-mappings/" rel="noreferrer"><code>ResultTransformer</code></a>.
The <code>DistinctPostResultTransformer</code> looks as follows:
<pre><code>public class DistinctPostResultTransformer
 extends BasicTransformerAdapter {
 
 private final EntityManager entityManager;
 
 public DistinctPostResultTransformer(
 EntityManager entityManager) {
 this.entityManager = entityManager;
 }
 
 @Override
 public List transformList(
 List list) {
 
 Map&lt;Serializable, Identifiable&gt; identifiableMap =
 new LinkedHashMap&lt;&gt;(list.size());
 
 for (Object entityArray : list) {
 if (Object[].class.isAssignableFrom(entityArray.getClass())) {
 Post post = null;
 PostComment comment = null;
 
 Object[] tuples = (Object[]) entityArray;
 
 for (Object tuple : tuples) {
 if(tuple instanceof Identifiable) {
 entityManager.detach(tuple);
 
 if (tuple instanceof Post) {
 post = (Post) tuple;
 }
 else if (tuple instanceof PostComment) {
 comment = (PostComment) tuple;
 }
 else {
 throw new UnsupportedOperationException(
 &quot;Tuple &quot; + tuple.getClass() + &quot; is not supported!&quot;
 );
 }
 }
 }
 
 if (post != null) {
 if (!identifiableMap.containsKey(post.getId())) {
 identifiableMap.put(post.getId(), post);
 post.setComments(new ArrayList&lt;&gt;());
 }
 if (comment != null) {
 post.addComment(comment);
 }
 }
 }
 }
 return new ArrayList&lt;&gt;(identifiableMap.values());
 }
}
</code></pre>
The <a href="https://vladmihalcea.com/fix-hibernate-hhh000104-entity-fetch-pagination-warning-message/" rel="noreferrer"><code>DistinctPostResultTransformer</code></a> must detach the entities being fetched because we are overwriting the child collection and we don’t want that to be propagated as an entity state transition:
<pre><code>post.setComments(new ArrayList&lt;&gt;());
</code></pre>

blocks|key|218702|text|此警告告诉您Hibernate正在内存中执行java分页。这可能会导致高JVM内存消耗。由于开发人员可能会忽略此警告，因此我为Hibernate添加了一个允许抛出异常的标志，而不是记录警告(https://hibernate.atlassian.net/browse/HHH-9965)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|218703|该标志为hibernate.query.fail_on_pagination_over_collection_fetch.|style|BOLD|218704|我建议每个人都启用它。|218705|该标志在org.hibernate.cfg.AvailableSettings中定义：|218706|++++/**
+++++*+Raises+an+exception+when+in-memory+pagination+over+collection+fetch+is+about+to+be+performed.
+++++*+Disabled+by+default.+Set+to+true+to+enable.
+++++*
+++++*+@since+5.2.13
+++++*/
++++String+FAIL_ON_PAGINATION_OVER_COLLECTION_FETCH+=+"hibernate.query.fail_on_pagination_over_collection_fetch";|code-block|syntax|javascript|218707|entityMap|0|LINK|mutability|MUTABLE|url|https://hibernate.atlassian.net/browse/HHH-9965^0|2N|1B|0|0|4|1K|0|0|4|Z|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|6|7|12|8|@$A|13|B|14|F|G]]|9|@]|C|$]]|$1|H|3|I|5|6|7|15|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|16|8|@$A|17|B|18|F|G]]|9|@]|C|$]]|$1|L|3|M|5|N|7|19|8|@]|9|@]|C|$O|P]]|$1|Q|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]]]

This warning tells you Hibernate is performing in memory java pagination. This can cause high JVM memory consumption.
Since a developer can miss this warning, I contributed to Hibernate by adding a flag allowing to throw an exception instead of logging the warning (<a href="https://hibernate.atlassian.net/browse/HHH-9965" rel="noreferrer">https://hibernate.atlassian.net/browse/HHH-9965</a>).

The flag is hibernate.query.fail_on_pagination_over_collection_fetch. 

I recommend everyone to enable it.

The flag is defined in org.hibernate.cfg.AvailableSettings :

<pre><code> /**
 * Raises an exception when in-memory pagination over collection fetch is about to be performed.
 * Disabled by default. Set to true to enable.
 *
 * @since 5.2.13
 */
 String FAIL_ON_PAGINATION_OVER_COLLECTION_FETCH = "hibernate.query.fail_on_pagination_over_collection_fetch";
</code></pre>

blocks|key|223662|text|正如其他人指出的那样，通常应该避免将"JOIN+FETCH“和firstResult/maxResults一起使用。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|223663|如果您的查询需要它，您可以使用.stream()来消除警告并避免潜在的OOM异常。|offset|length|style|CODE|223664|try+(Stream<ENTITY>+stream+=+em.createQuery(QUERY).stream())+{
++++ENTITY+first+=+stream.findFirst().orElse(null);+//+equivalents+.getSingleResult()
}|code-block|syntax|javascript|223665|//返回的Stream为IO流，需要手动关闭|223666|entityMap^0|0|F|9|0|0|5|6|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@$D|S|E|T|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|U|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|V|8|@$D|W|E|X|F|G]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|P|$]]

As others pointed out, you should generally avoid using &quot;JOIN FETCH&quot; and firstResult/maxResults together. 
If your query requires it, you can use <code>.stream()</code> to eliminate warning and avoid potential OOM exception.
<pre class="lang-java prettyprint-override"><code>try (Stream&lt;ENTITY&gt; stream = em.createQuery(QUERY).stream()) {
 ENTITY first = stream.findFirst().orElse(null); // equivalents .getSingleResult()
}
</code></pre>
// <code>Stream</code> returned is an IO stream that needs to be closed manually.

I'm getting a warning in the Server log "firstResult/maxResults specified with collection fetch; applying in memory!". However everything working fine. But I don't want this warning.

<h2>My code is</h2>

<pre class="lang-java prettyprint-override"><code>public employee find(int id) {
 return (employee) getEntityManager().createQuery(QUERY).setParameter("id", id).getSingleResult();
}
</code></pre>

<h2>My query is</h2>

<pre class="lang-java prettyprint-override"><code>QUERY = "from employee as emp left join fetch emp.salary left join fetch emp.department where emp.id = :id"
</code></pre>

How can I avoid the Warning "firstResult/maxResults specified with collection fetch; applying in memory!" when using Hibernate?

服务器

Java

我在服务器日志"firstResult/maxResults specified with collection fetch；applying in memory!"中收到警告。但是，一切都运行正常。但我不想要这个警告。我的代码是public employee find(int id) {    return (emp...

问如何避免出现警告"firstResult/maxResults specified with collection fetch；applying in memory!“什么时候使用Hibernate？
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