将本地数据库sqlite与生产服务器（MySQL）同步的最佳方法是什么？

Question

I am executing a sql query using transaction.executeSql() for sqlite db with Javascript (Cordova). I need the last executed query to store in table for future use (sync). I didn't find anything like that. Is there any suggestion?

db.transaction(function(tx) {
 tx.executeSql("Insert into tablename (id, name) Values(?,?);", values, function(tx, results) 
{
    // I need the last executed query here.
});

Data is being updated in the sqlite offline. When user clicks on "Sync" button I will have to push all updates by this user to the server. So, I thought I will store all queries executed by this user in a table. When he/she clicks on sync button I will just execute those query on live mysql.

Edit 1: This is not for backup purpose only. User can add some new item and update those. all of the other users should get this changes in their db after sync. And noteworthy, communication will be bidirectional. At first, the sqlitedb will be updated from live server, then I will execute all of the saved queries in the live server. This is the plan.

Is there any better approach?

Answer 1

If the size of your database is reasonable, you can compress it and synchronize the ".db.gz" file. If you store each SQL query and sync it, you might end up with something like this

DELETE FROM x where a=1
UPDATE x set a=2,b=3
INSERT INTO x set c=2

But if you sync the ".db" file it would ONLY contain INSERT statements, along with the schema definition. However,On the server side, you would need to efficiently import this into MYSQL.

If it's only for backup purposes, and you wouldn't need to generate any reports or you don't need to merge all those user data, you can survive with just storing the SQLite on the server. But I don't know what exactly is your project about.

Answer 2

I'm using sync in several enterprise apps with backends, this is my way:

1. Use SSL, if somehow possible.

2. In my workflow, the devices are registrate by scanning a barcode in the backend website. As a fall back the registration can be done on the device in a form.

3. I use encoding for the transfer datas. Every device has it's own code. The key comes via barcode/form to the device.

4. I have the following client tables in the backend:

   • tblClients: deviceUUID,deviceType, owner, encryptKey, createdDateTime, …
   • tblClientLogs: Logs all connections between device and backend
   • tblClientDelete: deviceUUID, tableName, rowUUID

5. In every table which has to be synced, I have a created and modified column. It's a datetime and created/modified are inserted by triggers.

6. On a sync task, the device is sending the UUID to the server, the server looks for a valid registration, rows which are created since last sync, rows which are modified since last sync and the row-delete-jobs.

7. The sync datetime is saved in tblClientLogs

8.The encrypted data, the backends send's to the client are objects and looking like:

tblWhatEver -> create -> {key:value, key:value, …}

or

tblWhatEver -> modify -> rowUUID {key:value, key:value, …}

or

tblWhatEver -> delete -> rowUUID

9. How the delete jobs are working. If some data are deleted in the backend, I'm looking for all deviceUUIDs and save in tblDeleteJobs:

deviceUUID, tableName, rowUUID

After a sync task the device-delete-job is deleted in tblClientDelete.

10. After receiving the data to the device, I decrypt it and create a sql statement for every data. The sql jobs are done by a loop.

11. After all jobs are done on the device I send a small report to the backend for checking if everything goes well.

12. In every device table I use UUIDs instead of integers to avoid collisions. On my devices you can send also datas to the server, it's working similar to the «downloads».

13. Timezone of my apps and the servers are the same, independent of the device location.

14. In the backend and the apps I have included a force sync from beginning, if something went's wrong.

15. In some apps I have some more options, there I can change the database, table structure via backend.