Question

考虑以下房间DAO

@Dao
public abstract class JobDao {

    @Insert
    public abstract long insert( Job v );

    @Update 
    public abstract int update( Job v );

    @Insert 
    public abstract long insertPerson( Person p );

    @Update
    public abstract int updatePerson( Person p );

    @Transaction
    public void insertNetJobs( List<NetJob> list ) {
         Timber.d("--- insert page start");
         for( NetJob j : list ) {
             if ( updatePerson( j.getPerson() ) == 0 ) {
                insertPerson( j.getPerson() );
             }

             insert( j.getJob() );
         } 
         Timber.d("--- insert page end");
    }  
}

根据文档，用@Transaction标记的方法中的任何内容都在单个事务中运行。但实际上，它为整个方法insertNetJobs运行一个事务，为每个调用updatePerson，insertPerson，insert的内部事务运行一个事务。所以日志看起来像这样

D/JobDao: ---- insert page start
D/SQLiteDatabase: beginTransaction() 
D/SQLiteDatabase: endTransaction()
                  beginTransaction()
D/SQLiteDatabase: endTransaction()
                  beginTransaction()
D/SQLiteDatabase: endTransaction()
                  beginTransaction()
........................
D/SQLiteDatabase: endTransaction()
                  beginTransaction()
D/SQLiteDatabase: endTransaction()
                  beginTransaction()
D/SQLiteDatabase: endTransaction()
D/JobDao: ---- insert page end

结果是方法insertNetJobs的工作非常缓慢。是否有可能仅使用一个事务来运行此方法？

Answer 1

尝试一下

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Answer 2

好的，我想出了问题所在。万一有人有类似问题，这里有一个解释。实际问题是更新查询。执行它大约需要20毫秒。

此代码：

   @Update
   public abstract int updatePerson( Person p );

生成以下查询：

UPDATE OR ABORT `sw_person` SET `id` = ?,`id_s` = ?,`id_lang` = ?,`name` = ? WHERE `id` = ?

此查询更新人员表的pk，但在其他表中，此键用作fk，导致在这些表中查找。遗憾的是，“房间”在更新查询中更新了pk，解决方案可能是手动编写查询。

Android Room DAO如何在单个事务中运行几种DAO方法？

2 个答案: