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Resolved SQLite database is replaced when the structure is modified

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  1. Gabriel Fortuny
    Gabriel Fortuny
  2. PowerServer Mobile (Obsolete)
  3. Monday, 3 December 2018 11:21 AM UTC

Hi,

 

First of all, thank you very much for the Elevate 2018 Recap Seminar of last week in Barcelona.

 

We're very interested in the PowerServer Mobile offline features and I'm testing the PowerServer Mobile in offline mode with an SQLite database, following this tutorial: https://www.appeon.com/support/documents/appeon_online_help/2.0/appeon_mobile_offline_tutorials/ch01.html

 

I have seen than when I modify the database's structure in my Desktop, the offline app notices it (using eon_offlineex object) and, once updated, no app database data is modified. If I ask the application to search for modifications once again it says that the structure has been modified (?) and, if I update the app database I see that the app database has been replaced.

 

If I only change information (not structure) in the tables of my desktop, the app doesn't see this changes because, I think, no database structure has been altered.

 

That is a strange behaviour that it's dangerous because if we modify the structure of the tables we don't want that the information on the device database be modified.

 

There is a way to avoid this behaviour?

 

Kind regards,

Gabriel Fortuny

  1. Offline
  2. PowerServer Mobile
  3. SQLite
Get the path of a selected file/Obtener la ruta de...
issue connecting to powerserver
Accepted Answer
Kai Zhao @Appeon
Kai Zhao @Appeon Accepted Answer Pending Moderation
  1. Wednesday, 5 December 2018 05:45 AM UTC
  2. PowerServer Mobile (Obsolete)
  3. # Permalink

Hi Gabriel,

Please set the start mode to 'Offline' in offline tab of application profile in Toolkit, thus the update not been downlaod to device automatically.

And please call of_applyupdate to update application only when there is any update. the db file would been update when call of_applydbupdate but not of_applyupdate.

Regards,
ZhaoKai

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Kai Zhao @Appeon
Kai Zhao @Appeon Accepted Answer Pending Moderation
  1. Tuesday, 4 December 2018 00:27 AM UTC
  2. PowerServer Mobile (Obsolete)
  3. # 1

Hi Gabriel,

SQLite doesn’t have a pre-built synchronization engine. You would have to develop your own synchronization.

The offline applications could connect to remote databases (through Appeon Server). You can create two transaction objects with one connecting SQLite (with DBParm "EnabledLocalDB='true'") and another connecting to the remote database (with DBParm "EnabledLocalDB='false'"), and then transmit data between both databases.

Regards,
ZhaoKai

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Gabriel Fortuny
Gabriel Fortuny Accepted Answer Pending Moderation
  1. Tuesday, 4 December 2018 08:07 AM UTC
  2. PowerServer Mobile (Obsolete)
  3. # 2

Dear ZhaoKai,

 

Thanks a lot for your answer.

 

But the problem is that when I modify the database's structure in my Desktop, the offline app notices it (using eon_offlineex object) and, once updated, no app database data is modified. If I ask the application to search for modifications once again it says that the structure has been modified (?) and, if I update the app database I see that the app database has been replaced.

As you say, we can control this behaviour with an remote database but no app database data should be replaced when we only change the structure.

 

And... I wonder if with an Ultralite database ocurrs the same.

 

Kind regards,

 

Gabriel Fortuny

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Gabriel Fortuny
Gabriel Fortuny Accepted Answer Pending Moderation
  1. Wednesday, 5 December 2018 08:14 AM UTC
  2. PowerServer Mobile (Obsolete)
  3. # 3

Dear ZhaoKai,

 

Thanks a lot again for your answer.

 

The offline.of_applyupdate() function documentation says that the local database is updated too but, as you say, it seems that only of_applydbupdate updates the local database:

 

 

Kind regards,

 

Gabriel Fortuny

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Kai Zhao @Appeon
  1. Kai Zhao @Appeon
  2. Thursday, 6 December 2018 00:37 AM UTC
Hi Gabriel,



Thanks for pointer this. we will correct the document.



Regards,

ZhaoKai
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