c++ - 如何在 SQLite 中传递用于触发函数的变量？

Question

/* 
// this is the trigger definition
CREATE TEMPORARY TRIGGER 'insertTrigger' INSTEAD OF INSERT ON 'foo' 
BEGIN 
    SELECT bar(NEW.id, NEW.timestamp); "
END; 
//*/

void insert(sqlite3 *db, char *id, char *timestamp, void *context){
    exec_query(db, "INSERT INTO foo(id,timestamp) VALUES(?,?)", id, timestamp);
}

void bar(sqlite3_context *context, int argc, sqlite3_value **argv){
    char *id = (char*)sqlite3_value_text(argv[0]);
    char *timestamp = (char*)sqlite3_value_text(argv[1]);
    //how do I get context* ???
    //this must be a thread safe function (i.e. multiple threads have their own sqlite3* and all execute queries (possibly including this one)
}

是否有一些解决方法可以启用此功能？就像一个想法:

void insert(sqlite3 *db, char *id, char *timestamp, void *context){
    sqlite3_mutex_enter(sqlite3_db_mutex(db));
    sqlite3_user_setdata(db, context); //this doesnt exist
    exec_query(db, "INSERT INTO foo(id,timestamp) VALUES(?,?)", id, timestamp);
    sqlite3_mutex_leave(sqlite3_db_mutex(db));
}

void bar(sqlite3_context *context, int argc, sqlite3_value **argv){
    char *id = (char*)sqlite3_value_text(argv[0]);
    char *timestamp = (char*)sqlite3_value_text(argv[1]);
    void *context_ = sqlite3_user_data(context);
}

似乎还有一些其他方法可以完成此操作，例如 sqlite3_get_auxdata 函数，但我不太了解该 api 的工作原理。

Answer 1

context 不是您查询的一部分，因此它在触发器函数中不可用。

毕竟，您发送的用于更新表的 SQL 语句可能(应该)根本不知道触发器!