Question

我正在使用GTFS并试图找到一种方法来加速我的内部联接。表“Trips”和“StopTimes”具有公共列“TripID”，表“StopTimes”和“Stops”具有公共列“StopID”。内部联接检索与特定Trip相对应的所有Stops，但是大约需要20秒。此外，“StopTimes”表包含900万行，而其他表包含数千行。以下代码是我的查询。

String joinQuery = "SELECT s.stop_id, s.stop_code, s.stop_name "
+ "FROM Trips as t INNER JOIN StopTimes as st ON     st.trip_id = t.trip_id "
+ "INNER JOIN Stops as s ON s.stop_id = st.stop_id "
+ "WHERE t.trip_id = " + TripID + " AND t.shape_id = " + ShapeID
+ " ORDER BY st.stop_sequence";

这是在创建数据库时执行的代码。

String CREATE_TRIPS_TABLE = "CREATE VIRTUAL TABLE " + TABLE_TRIPS + " USING FTS3("
            + KEY_T_ROUTE_ID + " INTEGER,"
            + KEY_T_NAME + " TEXT,"
            + KEY_TRIP_ID + " INTEGER,"
            + KEY_DIRECTION_ID + " INTEGER,"
            + KEY_SHAPE_ID + " INTEGER);";

    String CREATE_STOPS_TABLE = "CREATE VIRTUAL TABLE " + TABLE_STOPS + " USING FTS3("
            + KEY_STOP_ID + " INTEGER,"
            + KEY_STOP_CODE + " TEXT,"
            + KEY_STOP_NAME + " TEXT,"
            + KEY_STOP_LAT + " DOUBLE,"
            + KEY_STOP_LON + " DOUBLE,"
            + KEY_STOP_WHEELCHAIR + " INTEGER);";

    String CREATE_STOPTIMES_TABLE = "CREATE VIRTUAL TABLE " + TABLE_STOP_TIMES + " USING FTS3("
            + KEY_S_TRIP_ID + " INTEGER,"
            + KEY_S_STOP_ID + " INTEGER,"
            + KEY_ARRIVAL_TIME + " TEXT,"
            + KEY_STOP_SEQUENCE + " INTEGER,"
            + KEY_SHAPE_DIST_TRAVELLED + " DOUBLE);";

我遵循了我在这里找到的一些建议，但我仍然无法加快查询速度，感谢所有反馈。

更新我更改了我的表的创建方式，并为INNER JOIN查询中涉及的两个索引添加了索引，JOINS现在是即时的。

String CREATE_TRIPS_TABLE = "CREATE TABLE " + TABLE_TRIPS + "("
            + KEY_T_ID + " integer PRIMARY KEY AUTOINCREMENT,"
            + KEY_T_ROUTE_ID + " INTEGER,"
            + KEY_T_NAME + " TEXT,"
            + KEY_TRIP_ID + " INTEGER,"
            + KEY_DIRECTION_ID + " INTEGER,"
            + KEY_SHAPE_ID + " INTEGER);";

    String CREATE_STOPS_TABLE = "CREATE TABLE " + TABLE_STOPS + "("
            + KEY_S_ID + " integer PRIMARY KEY AUTOINCREMENT,"
            + KEY_STOP_ID + " INTEGER,"
            + KEY_STOP_CODE + " TEXT,"
            + KEY_STOP_NAME + " TEXT,"
            + KEY_STOP_LAT + " DOUBLE,"
            + KEY_STOP_LON + " DOUBLE,"
            + KEY_STOP_WHEELCHAIR + " INTEGER);";

    String CREATE_STOPTIMES_TABLE = "CREATE TABLE " + TABLE_STOP_TIMES + "("
            + KEY_ST_ID + " integer PRIMARY KEY AUTOINCREMENT,"
            + KEY_S_TRIP_ID + " INTEGER,"
            + KEY_S_STOP_ID + " INTEGER,"
            + KEY_ARRIVAL_TIME + " TEXT,"
            + KEY_STOP_SEQUENCE + " INTEGER,"
            + KEY_SHAPE_DIST_TRAVELLED + " DOUBLE);";

    db.execSQL(CREATE_ROUTES_TABLE);
    db.execSQL(CREATE_TRIPS_TABLE);
    db.execSQL(CREATE_STOPS_TABLE);
    db.execSQL(CREATE_STOPTIMES_TABLE);
    db.execSQL("CREATE INDEX T_id ON Trips(trip_id)");
    db.execSQL("CREATE INDEX S_t_id ON StopTimes(trip_id)");

Answer 1

我发现您正在使用SQLite's FTS3 extension，旨在提高全文搜索的效果。我怀疑你发出的查询类型（以及通常针对GTFS数据运行的查询类型）实际上是在对你不利。

我建议您首先创建一个传统的关系数据库，在相应的列上包含索引，然后针对该数据库测试查询的性能。当在这种类型的应用程序中使用时，SQLite肯定能够提供良好的性能，所以我认为你会感到惊喜。一旦您使用传统技术证明了成功，您可以查看其他方法，以便在必要时更快地运行查询。

最后，请注意SQLite does not allow indices on virtual tables，我怀疑这是您的查询现在需要很长时间才能完成的具体原因。

优化SQLite内部联接查询 - Android

1 个答案: