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I have a C++ application that stores data in a database (SQLite) through QxOrm.

It is clear that in the next versions, columns are gonna be added/removed/renamed, so I would like to set a version number to each database created, so that when someone tries to load a database it compares its version with the current version of the application and automatically add/remove/rename the columns to match the current schema.

I couldn't find in the QxOrm documentation something that would look like:

qx::QxSqlDatabase::getSingleton()->setVersion(2);

So first is it possible to do that kind of thing with SQLite? and if not should I just create a table that would hold the database version?

talnicolas
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2 Answers2

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A database version is perhaps not enough : you should store a version per persistent class (and maybe other informations per persistent class, like list of columns for example). When you register a persistent class into QxOrm context, you have to put a version number :

QX_REGISTER_HPP_XXX(myClass, myBaseClass, myClassVersion)

You can find some informations about creating a SQL schema into the FAQ of QxOrm library : http://www.qxorm.com/qxorm_en/faq.html#faq_230

Using introspection engine of QxOrm library, it's quite easy to do, more details about introspection engine here : http://www.qxorm.com/qxorm_en/faq.html#faq_190

You should create a table into your database to store a state for each persistents classes : you can store a version number per class, a list of columns, etc... Then it will be quite easy to compare 2 versions of persistent class to modify your SQL schema.

QxOrm
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  • Thanks! Glad to see you opened an account on SO! If you want me to put some more information in the QxOrm tag for you let me know! – talnicolas Apr 06 '12 at 12:20
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Now, you have QxEntityEditor application to manage your database schema evolution. QxEntityEditor is a multi-platform and cross-database graphic editor for QxOrm library. A video presentation of QxEntityEditor features is available here : http://www.qxorm.com/qxorm_en/tutorial_4.html

QxOrm
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