数据库设计，有关实现的问题

Question

Question regarding my sql database design for a project i am working on.

I will be receiving data every few seconds and i am going to need to store that data into a database. I am using mySQL for my DBMS. The data needs to be stored in the database with a userid attached to each piece of data. I will only be handling one user per application. So, each instance of the application will only be handling one users data. The remote database will be storing all users data though. So, that is why i need userid's to know whose data is whose.

My idea was to wait until i receive like 50 data packets and create a delimited string of all 50 data packets. (Maybe separated by commas) Then push that string to the database along with the userid. And store the data like that. My question is, is that a good way to do it? Is there a better way? Is this bad practice? TIPS PLEASE! =)

I will be receiving a lot of this data. One data packet like every second, sometimes faster. Just let me know what you think.

The DBMS will be running on a remote machine. The application will be running on an android phone.

Thanks in advance!

Answer 1

I would not suggest concatenating a bunch of values together to send a delimited string to the database. That just creates additional work on the database to parse the string.

Any reasonable framework for interacting with the database will let you create and send batches of SQL statements with different values for the bind variables to the database. That keeps the nice, friendly syntax of the stored procedure or INSERT statement, it keeps the database properly normalized, and it accomplishes the performance goal of minimizing the number of round-trips.

Answer 2

The question you really have to answer is the tolerance you have for losing data. A request per second transferring under 1k of data isn't much, especially using json vs. xml. Then again, battery life is something to keep in mind on mobile devices, so making a request every 5-60 seconds is also doable.

There's no reason you cannot batch your updates to the server.

If you have no tolerance for data loss, you could collect your batch of 50 updates on local storage, and upload them. If a failure occurs in transmission you can resend. In this case, however, I would want to have some record ID that's reasonably guaranteed to be unique, such as a UUID. This way the server can see which records it's already processed and exclude them from reprocessing.

Answer 3

If the dbms is running on a good server, and all you do with the data is a simple insert to a reasonably simple table, 1 insert per second should not a strain at all. I'd expect it to be hardly measurable.

Answer 4

I'm going to address the issue of storing it as a delimited string. HOw do you intend to query this data after it is stored? If you will need to find the data for one or aeven a small group of values but not the entire string, donot consider storing the data this way as it will give you horrible performance in querying and will be very painful to write queries for. In general, storing more than one piece of dat ina field is a bad thing, it means you need a related table.

Also, for what you are doing, if you don't need to to analytical querying of the data, perhaps a nosql database would be a better choice than a relational database.