i have the problem that when i release new version of my application, if i add a new column to one of my db tables, the database doesn't update. Any one know how to create a script of upgrade versione in case there are new columns or new tables??
Thanks
You have to remember that CreateTable it's already doing the columns update for you, because internally it calls a method called MigrateTable.
However you could have to handle more advanced modification to your database, like adding triggers or something similar.
In that case i suggest you to perform modifications manually.
In Xamarin Forms i've ended up with this:
https://gist.github.com/matpag/b2545cc22c8e22449cd7eaf6b4910396
Could not be the best strategy ever but seems to work for me.
Summarizing :
You have to save the database version in an internal flag of the SQlite database called user_version accessible with PRAGMA keyword.
Every time you get the database connection, you have to perform a check and see if the current database version is the same as the app last database version.
If not you need to perform a database update and set the new current version.
It's not a matter of a script, as there isn't such a thing. You can release a version with a "patch" that will run once, extracting all your records to a temporary form -> deleting the table -> creating it again (will assure it's created with the new columns and so on) -> reinserting the records again. After a while, when you know that all your users (or whenever you set the limit) have moved to the newer version you can just eliminate the "patch" from your code.
Hope it helps.
The automatic migration feature is still not working in sqlite.net-pcl, but it looks like it does work in the other sqlite package: sqlite-net-pcl, which is actually the Xamarin recommend sqlite package.
Related
This is my first time working on a Xamarin App and I am new to the app development world so I need some help figuring out this process.
Currently I run a php web service that generates some SQL files that I run in DB Browser and I get a database file which I then put into my Assets and Resources Folder. Using each platform's API I copy the database into a writable folder and use that to run my queries.
I followed this really helpful tutorial and it worked perfectly fine.
https://medium.com/#hameedkunkanoor/creating-a-sqlite-databse-and-storing-your-data-in-your-android-and-ios-application-in-xamarin-2ebaa79cdff0 .
After the "initial" setup I store a timestamp in a local table and and the next time the user opens the app I pass that timestamp and retrieve data that is older than that timestamp. The I update that timestamp and continue the process. That data is sent back in JSON format and make the updates to the tables.
My only concern is if a new version were to come out where I add a new table or a new column which is not present in the current version of my Database, how should I take care of those update Web Service calls? Is there a way of monitoring my DB version? I read somewhere where I could just ignore the new data that is not present already, like table or columns, but I'm not really sure how to do that.
I also saw that if I call CreateTable on my current tables I could potentially update them?
Also for future reference each time I develop a new app would I need to regenerate a new database file to store in the assets/resources folder? Is there a more automated process for this? Along with monitoring the version of my database?
Any Help/Tutorials/Suggestions would be greatly appreciated.
You have to remember that CreateTable it's already doing the columns update for you, because internally it calls a method called MigrateTable which you can see here for further clarification: https://github.com/praeclarum/sqlite-net/blob/master/src/SQLite.cs#L562.
However you could have to handle more advanced modification to your database, like adding triggers or something similar.
In that case i suggest you to perform modifications manually.
In Xamarin Forms i've ended up with this:
https://gist.github.com/matpag/b2545cc22c8e22449cd7eaf6b4910396
Could not be the best strategy ever but seems to work for me.
Summarizing :
You have to save the database version in an internal flag of the SQlite database called user_version accessible with PRAGMA keyword.
Every time you get the database connection, you have to perform a check and see if the current database version is the same as the app last database version.
If not you need to perform a database update and set the new current version.
Reference here.
I don't want to upgrade the database version but I want to change some values of a column when I release a new version of my android app. where is the right place for writing update query?
SQLiteOpenHelper not really help you as it not know you want changes made. It designed to see database version.
So the place is when you open the database and then after you have checked if the changes need to be made else every time App starts changes would be done.
You could be introduce a table to save data about the changes. It could be checked to see is the changes has been applied. At first if the table does not exist then first updates would be applied.
You could have the App override onOpen or onConfigure for the App release for the specific release you have to consider new install verse old.
Amount of data and hardness could decide right way. A lot of data and you could have issue if check would be all data. So small table, even 1 row could be way to go.
I'm trying to figure out the best way to handle database upgrades and versioning.
At the moment I delete the database and log users out when I do a point release, which isn't a great experience.
Can anyone recommend any tips for doing this?
Your database version is independent of your app version. If your database schema doesn't change at all, you shouldn't need to do anything to your database during an update.
When your database schema changes, you should handle database updates in onUpgrade() of your SQLiteOpenHelper. This method is called when you try to access your database and you have updated your database version, as described in the Data Storage Options documentation.
If you are using a third party library to handle your databases, it should either handle the upgrade for you or provide similar functionality.
There is no universal strategy for upgrading your database here. What you do depends completely on what your schema looked like before the upgrade and what the new schema looks like. Depending on what changed, you might create new tables or columns, delete tables or columns, update rows in the database, or move data between tables. If you have a specific question about how to migrate your data, create a new question describing the new and old schemas.
The way we do it is that we run a routine every time the app starts that calls a stored proc on the server to get SQL that upgrades the database if it is necessary. (The sql can be quite involved: dropping tables and recreates them with new structures and inserting new values). We store the version of the database in the database itself and upgrades to the new version.
We don't use the onUpgrade() call.
I am creating a simple application that uses a database derived from db = SQLiteDatabase.openOrCreateDatabase(...). Now, when I create it I use db.setVersion(1);
And I read somewhere that I have to change the database version each time I change it. Now I can't find the particular tutorial where I read this, so I am left with some questions.
1)What is the reason behind versioning of a database? What is a practical purpose?
2)When exactly should the version be updated? After every insert? Every additional table added?
3)Will I be in trouble if I don't update the versions after 1? What would it lead to?
1)Versioning the database is really versioning your schema. This allows you to know when the schema is changed so you can convert it.
2)Whenever you change the schema.
3)If you change the schema, you won't know which one is being used and will end up with exceptions. If you never change the schema, nothing will happen.
And you shouldn't be manually calling setVersion. It already knows the version for an existing one, and you pass in the version elsewhere if its a new database.
The SQLite Database Version In Android is only neccessary if you manage database creation and version updates with the SQLiteOpenHelper.
SQLiteOpenHelper takes care of
opening the database if it exists,
creating it if it does not exis,
upgrading its schema if necessary
sets the SQLite Database Version.
The databaseverionnumber is set in the SQLiteDatabase-constructor.
Your example SQLiteDatabase.openOrCreateDatabase(...) does not use SQLiteOpenHelper so in this case there is no need set the dbversion.
I have a database that I built in SQLite browser, and it works fine. I launched an app with a prebuilt database and now I want to add more tables and data to that database.
I can get the app to launch the onUpgrade() method of the SQLiteOpenHelper. But the problem is, it's doing that EVERY time I use the helper.
I have it localized to, only on app launch, separating the upgrade command from the helper I used to retrieve data, but this is still a problem.
I have figured it out though, as I have been using the same database on my computer (the one that I'm editing) since version 1. So, whenever it writes the newer database onto the SD card it's showing version 1 even though I should be up to version 4 by now.
So, my question is, how can I manually edit the database version of the original database so that when it updates it isn't writing the old version number over the new one?
To manually update the version to 4 you execute the following SQL statement:
PRAGMA user_version = 4
Another way to change the version of your Sqlite Database. You can use DB Browser for SQLite:
Open the database file with "DB Browser for SQLite".
Change the "User Version" number to whatever number you want
Click the "Save" button
You can also set it via the setVersion SqlLiteDatabase method.
Source: http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html#setVersion(int)