postgresql - 如何清理 Spring Boot 应用程序中的数据库表？

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 注释函数会导致:

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

以下是可行的，但感觉错误得很危险:

    @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()
    }

正确的做法是什么？

Answer 1

您只需注入(inject) DataSource，从中获取连接，执行作业，然后关闭连接。

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

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

注意 use 的用法，它会在 block 执行后关闭连接。