Use provider built-in result count to reuse query if possible

[quaff]

Hibernate introduce SelectionQuery::getResultCount since 6.5.0, It may be JPA Query method in the future.

[christophstrobl]

Thank you @quaff for bringing this up. Did you eventually compare the resulting database interaction triggered by getResultCount to the count as it is done right now? Before we change the current behaviour I'd like to understand potential implications on both what the count query looks like as well as potential runtime implications.

[quaff]

Thank you @quaff for bringing this up. Did you eventually compare the resulting database interaction triggered by getResultCount to the count as it is done right now? Before we change the current behaviour I'd like to understand potential implications on both what the count query looks like as well as potential runtime implications.

Please refer to https://github.com/hibernate/hibernate-orm/blob/8c3b68cd784076a06a4bc2a7a3d67fc32904dba3/hibernate-core/src/main/java/org/hibernate/query/sqm/tree/select/SqmSelectStatement.java#L465

[mp911de]

This PR isn't complete. I took a look at a complete implementation and pushed my variant on https://github.com/spring-projects/spring-data-jpa/tree/issue/3456.

[mp911de]

Using SelectionQuery.getResultCount() only works when there's an enclosing transaction, otherwise the underlying Session will be closed.

[mp911de]

Thanks for the suggestion. We've implemented a variant via cdcac86.