[hibernate-issues] [JIRA] (HHH-15719) Hint UniqueSematics.NONE for entity queries without collection join fetches

Christian Beikov ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) *created* an issue Hibernate ORM ( https://hibernate.atlassian.net/browse/HHH?atlOrigin=eyJpIjoiYWEwM2YxNTg5... ) / Improvement ( https://hibernate.atlassian.net/browse/HHH-15719?atlOrigin=eyJpIjoiYWEwM2... ) HHH-15719 ( https://hibernate.atlassian.net/browse/HHH-15719?atlOrigin=eyJpIjoiYWEwM2... ) Hint UniqueSematics.NONE for entity queries without collection join fetches ( https://hibernate.atlassian.net/browse/HHH-15719?atlOrigin=eyJpIjoiYWEwM2... ) Issue Type: Improvement Assignee: Christian Beikov ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) Components: hibernate-core Created: 15/Nov/2022 01:59 AM Fix Versions: 6.1.6 Priority: Major Reporter: Christian Beikov ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) In the constructor of org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan we currently always choose ListResultsConsumer.UniqueSemantic.ALLOW , but it would be better to use this instead: sqm.containsCollectionFetches() ? ListResultsConsumer.UniqueSemantic.ALLOW : ListResultsConsumer.UniqueSemantic.NONE The deduplication showed up on some flame graphs and I realized that in that particular case it is not even necessary, because only collection join fetches alter the cardinality such that duplicates are possible. Maybe non-attribute joins could alter the cardinality as well, so it might be worth being pessimistic about this for now. We could detect some non-cardinality altering cases though if we want. ( https://hibernate.atlassian.net/browse/HHH-15719#add-comment?atlOrigin=ey... ) Add Comment ( https://hibernate.atlassian.net/browse/HHH-15719#add-comment?atlOrigin=ey... ) Get Jira notifications on your phone! Download the Jira Cloud app for Android ( https://play.google.com/store/apps/details?id=com.atlassian.android.jira.... ) or iOS ( https://itunes.apple.com/app/apple-store/id1006972087?pt=696495&ct=Em... ) This message was sent by Atlassian Jira (v1001.0.0-SNAPSHOT#100210- sha1:28a3636 )