Spring 数据 JPA native 查询跳过锁定

Question

我想执行一个 SKIP LOCKED使用 Spring Data JPA 在 Oracle 上查询，所以我尝试了以下操作:

@Lock(LockModeType.PESSIMISTIC_WRITE)
@Query(value = "SELECT * FROM User WHERE ID=?1 FOR UPDATE SKIP LOCKED", nativeQuery = true)
User findOne(UUID id);

我尝试了以上，发现生成的查询包含FOR UPDATE ，但不是 SKIP LOCKED (以下是从日志生成的查询):

select ent0_.column1 as name, ent0_.CREATED_DATE as CREATED_2_33_0_ from TABLE_NAME alias_name where ent0_.column1=? for update

如果我删除 @Lock从查询方法来看，生成的查询甚至没有FOR UPDATE .

请建议我如何使用 FOR UPDATE SKIP LOCKED 生成查询， 按要求。

Answer 1

你可以给 -2超时值，以便尽可能使用“跳过锁定”。

PESSIMISTIC_WRITE with a javax.persistence.lock.timeout setting of -2

UPGRADE_SKIPLOCKED

The lock acquisition request skips the already locked rows. It uses a SELECT …​ FOR UPDATE SKIP LOCKED in Oracle and PostgreSQL 9.5, or SELECT …​ with (rowlock, updlock, readpast) in SQL Server.

public interface MyRepository extends CrudRepository<MyEntity, Long> {

    /**
     * The lock acquisition request skips the already locked rows.
     * It uses a SELECT …​ FOR UPDATE SKIP LOCKED in Oracle and PostgreSQL 9.5,
     * or SELECT …​ with (rowlock, updlock, readpast) in SQL Server.
     */
    String UPGRADE_SKIPLOCKED = "-2";

    @Lock(value = LockModeType.PESSIMISTIC_WRITE) // adds 'FOR UPDATE' statement
    @QueryHints({@QueryHint(name = "javax.persistence.lock.timeout", value = UPGRADE_SKIPLOCKED)})
    MyEntity findFirstByStatus(String status);

}

通过这样做，选择查询将有 select ... for update skip locked
https://docs.jboss.org/hibernate/orm/5.0/userguide/html_single/chapters/locking/Locking.html