Question

我目前的尝试（根据this answer）如下所示：

@Service
class VacuumDatabaseService(
        private val entityManager: EntityManager
) {
    fun vacuumAllTables() {
        val session = entityManager.unwrap(org.hibernate.Session::class.java)
        val sessionImpl = session as org.hibernate.internal.SessionImpl
        val connection = sessionImpl.connection()
        connection.prepareStatement("VACUUM FULL").execute()
    }
}

但是它抛出：

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.IllegalStateException: No transactional EntityManager available

用@Transactional注释功能会导致：

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.reflect.UndeclaredThrowableException

Caused by: org.postgresql.util.PSQLException: ERROR: VACUUM cannot run inside a transaction block

以下方法有效，但感觉很危险：

    @Transactional
    fun vacuumAllTables() {
        val session = entityManager.unwrap(org.hibernate.Session::class.java)
        val sessionImpl = session as org.hibernate.internal.SessionImpl
        val connection = sessionImpl.connection()
        connection.prepareStatement("END TRANSACTION; VACUUM FULL;").execute()
    }

正确的方法是什么？

Answer 1

您只需要注入DataSource，断开连接，执行您的工作，然后关闭连接。

@Service
class VacuumDatabaseService(
        private val dataSource: DataSource
) {

    fun vacuumAllTables() {
        dataSource.connection.use {
            it.prepareStatement("VACUUM FULL").execute()
        }
    }
}

请注意use的用法，一旦执行该块，它将关闭连接。

如何在Spring Boot应用程序中清理数据库表？

1 个答案: