Question: Setting Serialized Mode in PCL

[sudmanche]

Hi, in non PCL version of SQLite.Net I was able to do this for Android and iOS:

        SQLite.SQLite3.Shutdown();
        SQLite.SQLite3.Config(SQLite.SQLite3.ConfigOption.Serialized);
        SQLite.SQLite3.Initialize();

and this would stop the threading error.

I cannot see how to set serailize mode with the PCL. Can you explain please.

[sudmanche]

searching through the code I have found that in SQLite.Net.Interop.ISQLiteApi the following line.

    //        Result Config(ConfigOption option);

so the ability to set the config is not implemented. Is there a reason why? With the non-PCL I had to set Serialized to avoid getting SIGSEVC errors on multi thread access.

[oysteinkrog]

I'm not sure why this is, it might simply be a mistake.
Does everything work if you uncomment it?

[sudmanche]

unfortunately not!

it seems all of these are not implemented in the Internal, or defined in the interface.

    [DllImport("sqlite3", EntryPoint = "sqlite3_initialize", CallingConvention=CallingConvention.Cdecl)]
    public static extern Result Initialize();

    [DllImport("sqlite3", EntryPoint = "sqlite3_shutdown", CallingConvention=CallingConvention.Cdecl)]
    public static extern Result Shutdown();

    [DllImport("sqlite3", EntryPoint = "sqlite3_config", CallingConvention=CallingConvention.Cdecl)]
    public static extern Result Config (ConfigOption option);

I'll see what I can do to test the implementation of these, but I do not have an environment to build for all platforms unfortunately.

[sudmanche]

I have attempted to make the necessary changes to add in this functionality. As mentioned I cannot do all platforms, and some I have no ability to test. I am testing for Xamarin iOS and Android.

the changes I have made to source are

1. In SQLite.Net.Interop.ISQLiteApi
   add in extra items to the Interface.

   Result Initialize();
   Result Shutdown();
   Result Config(ConfigOption option);
   

2. In each Platform - SQLiteApi[Platform]Internal.cs file
   add relevant dllimports (win32 uses Interop, WinRT has none) as below (config was defined, but no concrete implementations)

   [DllImport("sqlite3", EntryPoint = "sqlite3_initialize", CallingConvention = CallingConvention.Cdecl)]
   public static extern Result sqlite3_initialize();
   
   [DllImport("sqlite3", EntryPoint = "sqlite3_shutdown", CallingConvention = CallingConvention.Cdecl)]
   public static extern Result sqlite3_shutdown();
   

3. In each SQLiteApi[Platform].cs file
   add concrete implementations

   public Result Initialize()
   {
       return SQLiteApiAndroidInternal.sqlite3_initialize();
   }
   public Result Shutdown()
   {
       return SQLiteApiAndroidInternal.sqlite3_shutdown();
   }
   
   public Result Config(ConfigOption option)
   {
       return SQLiteApiAndroidInternal.sqlite3_config(option);
   }
   

++++++++++++++++++

Ok, so I have only done some limited testing so far, but seems to solve my problem which was on Android. I have not touched WindowsPhone8 as I cannot load it into VisualStudio.

What would you like me to do with the files I have modified? I could (try) and create a fork on Git hub and commit them up? (note: I am not very familiar with Git, but am willing to try this), or zip them up and send them to you, or maybe you don't need/want them anyway.

[sudmanche]

tried to contribute my changes by creating a pull request, but it did not work as I expected.
I really don't know what I have to do in Git & GitHub to contribute my changes.

[sudmanche]

Have now forked and committed the files I have changed. let me know what to do next?

https://github.com/sudmanche/SQLite.Net-PCL

[oysteinkrog]

Hi, to create a pull request you should create a new branch on your repo and then you can use github to create a PR.

Regarding this change, I think it's a good idea to add it back, but I fear there are some platforms that do not support/implement the necessary sqlite3 functions.
I am not 100% sure how to handle it in those cases, I see at least two viable options:

1. Add a new interface (e.g. ISQLiteApiEx) for the new functions, then consumers can check if the platform supports it by using the is/as keywords.
2. Have the unsupported exceptions throw NotSupportedException

[has-taiar]

So has this been merged?

@oysteinkrog , throwing a NotSupportedException is the right thing in this case, as the operation IS really not supported on that platform.
I have just spent an hour migrating from SQLite.NET to this library and I am very happy with the results, but I need to have the ability to change the config as this causes issues with multi-threading apps.
Any idea when would this be merged?

Thanks a lot for the great effort everybody :)

[oysteinkrog]

Hi @has-taiar, nothing has been merged yet.
I think I agree that a NotSupportedException is the best solution, I would be happy to merge a PR that included that.

[sudmanche]

I have attempted to do all neccessary changes, and created a pull-request #39.
hope this helps and is correct.