Query and CountQuery Concurrently Java Spring JPA?-CodePudding

I have a query that requires pagination and I want to run the query and countQuery at the same time. I also want to get the result in a Page object so I know how many items, total count, nextPage etc. I am not sure if this is possible without some sort of custom implementation.

Lets say I have something like this @Query(value="select * from users where tag=tag;" countQuery="select count(*) from (select * from users where tag=tag) as qcount") Page<User> getUsersWithTag(Tag tag, Pageable pagination) Is it possible to run both the count and query at the same time and get a Page result? I am thinking about using springs @Async annotation, I guess these methods would have to be split apart.

I have tried just adding @Async onto the method but that seems to actually hurt the performance. I am aware I may need to use Future or CompletableFuture to do this, just not sure how I can get the Page information together.

Update: I have found somewhat of a hacky soltuion but basically using java Futures and Spring Async I have done this.

@Query(value="select * from users;")
@Async 
Future<Page<User>> getUsersWithTag(Tag tag, Pageable pagination)

@Query(value="select count(*) from (select * from users where tag=tag) as qcount")
@Async
Future<Long> getUsersWithTagCount(Tag tag, Pageable pagination)

List<User> users = getUsersWithTag(tag, pageable).get();
long count = getUsersWithTagCount(tag, pageable).get();
Page<User> = new PageImpl<>(users, pageable, count);

CodePudding user response：

You already have this information in your paged result set

Page<User> getAllUsers(Pageable pagination)

You return Page<User> and there you have available the method getTotalElements() which should return to you the total number of elements contained in all pages.

Also

@Query(value="select * from users;" countQuery="select count(*) from (select * from users) as qcount") Page<User> getAllUsers(Pageable pagination)

The part countQuery="select count(*) from (select * from users) as qcount" is redundant as spring will by default create and use the same query by itself, only because you use Pagination in your declared method.

CodePudding user response：

With org.springframework.data.domain.Page you already have :

{ "totalElements": 0, "totalPages": 0, "size": 0, "content": [ {...

See Page doc for more details.