Question

I am developing an iPhone application that retrieves the data from remote MySQL server. As database is huge i don’t want to download data each time application runs, rather then i just want to download the data only one time then sync with SQLite database.(No need to download again and again)

If there is an update on remote MySQL server then only download the updated data.

If there is an insert operation on Remote MySQL server then i can identify from the last inserted ID of database table by comparing primary key values.But How to check for Delete and Update operation with Best efficiency so i just need to download minimum data as a result of delete or update operation?

Any help and suggestion would be appreciated.

Thanks,

Jim.

Answer 1

First off, I would say instead of doing a big first-time download, why not ship your app with a copy of the database instead? Then all you have to worry about is incremental updates.

If the database isn’t being modified constantly, I think the easiest way to do this would be leveraging a query log. Turn on query logging on the MySQL DB so that all operations are recorded to a file. Then, when the iPhone requests updated data, you can simply parse the log file and prepare a response that describes inserts, updates, and deletes.

If the database is being modified by many users in real time, this isn’t really a good idea since the query log would be enormous. In that case, you can use createdOn/modifiedOn timestamps in the database to know which inserts and updates are candidates for the iPhone response. For deletes though, you could either mark each row as “not really deleted” until the iPhone app is made aware, or you could create a table called “deleted data” and move stuff into there instead of explicitly deleting it.