Tag Archives: Windows 8.1

Building Windows Phone, Windows and Universal Apps: Winter Events Series!

*Update*: Apologies, we’ve had to cancel the Dev Workshop on Thursday 20th November.

In the late summer, we held a series of events aimed at Windows Phone and Windows 8.1 app developers intended to help you along the road to getting an app published in the Windows Store, whether you are a complete beginner or a more experienced app developer.

We are running a new series of those events this winter. We start with two one-hour webinars run back-to-back, follow those with a one day workshop at Microsoft’s offices in Victoria, London, and wrap up with a ‘Publish to the Store’ hack event again at Microsoft London:

Webinar 1: Windows Apps JumpStart LIVE Series – Kick Starter Webinar for the non C#/XAML developer: This one hour webinar is aimed at developers who are completely new to Visual Studio, XAML, C# and .NET. This will give you what they need to get started with downloading Visual Studio, a little bit of knowledge of C# and the structure of a XAML-based app.
Online webinar
Friday 7 Nov 2014  10:00 –11:00
Registration: http://aka.ms/winappswebinar1

Webinar 2: Windows Apps JumpStart LIVE Series – JumpStart Webinar: Building Universal Apps with C# and XAML: This one hour webinar follows on straight away after the previous one. It is aimed at developers who are new to Windows Store app development, but who have some experience of developing software using .NET, or for those who have attended the previous webinar.
Online webinar
Friday 7 Nov 2014    11:00 – 12:00
Registration: http://aka.ms/winappswebinar2

Following on from the webinars, we have a one-day dev camp:

Dev camp: Windows Apps JumpStart LIVE Series: Windows Apps Dev Workshop
This one day event will be help at Microsoft’s offices near Victoria Station, London, running 9:30 – 17:30. At this workshop, you will learn how to program Windows and Windows Phone apps, including universal apps that run on both. There will be Hands-on Labs available, and you can get tips and advice from Microsoft experts and from peers in the developer community. There’ll be some giveaways as well Smile
Dev camp
Sorry! This one has had to be cancelled…

And following on from that, we have a one-day Publish hackathon:

Publish event: Windows Apps JumpStart LIVE Series: Publish Hackathon
This informal one-day event will also be held at Microsoft’s building in London, running 9:00 – 21:00 on a Saturday. This is a fun 12 hour event encouraging developers to bring their existing projects (apps/cloud projects) to polish and publish through to the last mile with help from Microsoft and community experts. There’ll be pizza and drinks and prizes too!
Publish Hack event
Saturday 13 December 2014
    09:00 – 21:00
Registration: http://aka.ms/winappspublishhack

Come along and join us – and if you don’t manage to publish an app this quarter, remember we are repeating these events again the first half of next year so you can get started now and then come and join us again later!

Windows Apps JumpStart LIVE Events Series

We’re starting a new series of events for UK developers that will help you on the journey from initial interest in developing apps for Windows 8 and Windows Phone right the way through to publishing an app to the Windows Store. You can join into the series at whichever point makes sense to you, so whether you’ve never opened Visual Studio before or written a line of C#, or you’re a developer who has already written software using out tools and languages but are new to apps, we can help you get to that point where you’re publishing your first app into our store. And we’re going to repeat the series of events every quarter, so you can jump on and off the series and attend events at whatever pace makes sense to you.

We start with two one-hour webinars run back-to-back:

Webinar 1: Windows Apps JumpStart LIVE Series – Kick Starter Webinar for the non C#/XAML developer: This one hour webinar is aimed at developers who are completely new to Visual Studio, XAML, C# and .NET. This will give you what they need to get started with downloading Visual Studio, a little bit of knowledge of C# and the structure of a XAML-based app.

Webinar 2: Windows Apps JumpStart LIVE Series – JumpStart Webinar: Building Apps with C# and XAML: This one hour webinar follows on straight away after the previous one. It is aimed at developers who are new to Windows Store app development, but who have some experience of developing software using .NET, or for those who have attended the previous webinar.

Following on from the webinars, we have a one-day dev camp:

Dev camp: Windows Apps JumpStart LIVE Series: Windows Apps Dev Workshop
This one day event will be help at Microsoft’s offices near Victoria Station, London, running 9:30 – 18:00. At this workshop, you will learn how to program Windows and Windows Phone apps, including universal apps that run on both. There will be Hands-on Labs available, and you can get tips and advice from Microsoft experts and from peers in the developer community.

And following on from that, we have a one-day Publish hackathon:

Publish event: Windows Apps JumpStart LIVE Series: Publish Hackathon
This informal one-day event will also be held at Microsoft’s building in London, running 9:00 – 21:00 on a Saturday. This is a fun 12 hour event encouraging developers to bring their existing projects (apps/cloud projects) to polish and publish through to the last mile with help from Microsoft and community experts.

First events are coming up fast!:

Come along and join us – and if not this quarter, remember we are repeating these events throughout the year so you can join us when you can!

Windows Apps JumpStart LIVE Events Series

We’re starting a new series of events for UK developers that will help you on the journey from initial interest in developing apps for Windows 8 and Windows Phone right the way through to publishing an app to the Windows Store. You can join into the series at whichever point makes sense to you, so whether you’ve never opened Visual Studio before or written a line of C#, or you’re a developer who has already written software using out tools and languages but are new to apps, we can help you get to that point where you’re publishing your first app into our store. And we’re going to repeat the series of events every quarter, so you can jump on and off the series and attend events at whatever pace makes sense to you.

We start with two one-hour webinars run back-to-back:

Webinar 1: Windows Apps JumpStart LIVE Series – Kick Starter Webinar for the non C#/XAML developer: This one hour webinar is aimed at developers who are completely new to Visual Studio, XAML, C# and .NET. This will give you what they need to get started with downloading Visual Studio, a little bit of knowledge of C# and the structure of a XAML-based app.

Webinar 2: Windows Apps JumpStart LIVE Series – JumpStart Webinar: Building Apps with C# and XAML: This one hour webinar follows on straight away after the previous one. It is aimed at developers who are new to Windows Store app development, but who have some experience of developing software using .NET, or for those who have attended the previous webinar.

Following on from the webinars, we have a one-day dev camp:

Dev camp: Windows Apps JumpStart LIVE Series: Windows Apps Dev Workshop
This one day event will be help at Microsoft’s offices near Victoria Station, London, running 9:30 – 18:00. At this workshop, you will learn how to program Windows and Windows Phone apps, including universal apps that run on both. There will be Hands-on Labs available, and you can get tips and advice from Microsoft experts and from peers in the developer community.

And following on from that, we have a one-day Publish hackathon:

Publish event: Windows Apps JumpStart LIVE Series: Publish Hackathon
This informal one-day event will also be held at Microsoft’s building in London, running 9:00 – 21:00 on a Saturday. This is a fun 12 hour event encouraging developers to bring their existing projects (apps/cloud projects) to polish and publish through to the last mile with help from Microsoft and community experts.

First events are coming up fast!:

Come along and join us – and if not this quarter, remember we are repeating these events throughout the year so you can join us when you can!

SQLiteWinRT: Opening databases shipped as app content or from an SD Card

Recently, I was asked about opening a database file inserted into a device on an SD card. I had to make a slight change to the SQLWinRT wrapper to enable it, so this post explains how, and also looks at opening databases shipped in the app package as content.

Opening databases shipped as content

You can include a prepopulated SQLite database in your Windows 8.x or Windows Phone app package. When the user installs the app, the database file ends up in the App Install folder where you can open it from your code – but only in a read-only fashion:

public static async void LoadDatabase()
{
    // Get a reference to the SQLite database
    db = new SQLiteWinRT.Database(
        Windows.ApplicationModel.Package.Current.InstalledLocation, 
        "customers.sqlite");

    await db.OpenAsync(SQLiteWinRT.SqliteOpenMode.OpenRead);

    // PRAGMA temp_files=2 causes temporary files to be created in memory
    // rather than in a physicalfile in the same folder as the database
    // Note that temp files only really get used if you are going to do 
    // complicated JOINs etc
    await db.ExecuteStatementAsync("PRAGMA temp_files=2");
}

If you want to have read-write access to the database, you must copy it from the install folder to the local folder first.

async Task CopyDatabaseAsync()
{
    // Has the database been copied already?
    try
    {
        await ApplicationData.Current.LocalFolder.GetFileAsync("customers.sqlite");
        // No exception? It exists...
        return;
    }
    catch (System.IO.FileNotFoundException)
    {   // Expected response - no-op 
    }

    StorageFile dbfile = await StorageFile.GetFileFromApplicationUriAsync(
        new Uri("ms-appx:///customers.sqlite"));
    await dbfile.CopyAsync(ApplicationData.Current.LocalFolder);
}

Opening a Database on an SD Card

A database file that you open from an SD Card is related to the previous case in that it is read-only. You cannot write to any file on an SD Card from any app in Windows Phone 8.

I haven’t researched it thoroughly, but you should be able to open a database file on removable storage in a Windows 8.x Store app. You will have to request the Removable Storage capability in the app manifest, and declare the file extensions you want to access in the app manifest as well. Then you should be able to get a StorageFile reference to the database file using techniques similar to those discussed here: http://lunarfrog.com/blog/2012/10/27/external-storage-devices/   . When I’ve tried it, I’ll update this post!

What I have tried though, is doing this on a Windows Phone 8 device that has an SD card slot, such as the Nokia Lumia 820. As with Windows 8, you have to declare the file extensions you want to access in the manifest. For example, add the following after the closing </Tokens> tag:

    <Extensions>
      <FileTypeAssociation Name="sqlite" TaskID="_default" NavUriFragment="fileToken=%s">
        <SupportedFileTypes>
          <FileType ContentType="application/sqlite">.sqlite</FileType>
        </SupportedFileTypes>
      </FileTypeAssociation>
    </Extensions>

Then in your code, you can open a read-only connection to the database as follows:

public static async void LoadDatabase()
{
    // Get a reference to the SQLite database
    ExternalStorageDevice _sdCard = 
        (await ExternalStorage.GetExternalStorageDevicesAsync())
        .FirstOrDefault();

    if (_sdCard == null)
    {
        MessageBox.Show("No SD Cards found");
        return;
    }
    else
    {
        ExternalStorageFile dbStoragefile = 
            await _sdCard.GetFileAsync("customers.sqlite");
        db = new SQLiteWinRT.Database(dbStoragefile.Path);
    }

    await db.OpenAsync(SQLiteWinRT.SqliteOpenMode.OpenRead);

    // PRAGMA temp_files=2 causes temporary files to be created in memory
    // rather than in a physicalfile in the same folder as the database 
    // Note that temp files only really get used if you are going to do 
    // complicated JOINs etc
    await db.ExecuteStatementAsync("PRAGMA temp_files=2");
}

Important: I had to modify the wrapper code posted up on http://sqlwinrt.codeplex.com in order to enable this usage. I added a new override of the Database object constructor that just takes the path to the database file as a string. Earlier versions had one override of the constructor that took a Windows.Storage.StorageFile parameter and another that took a Windows.Storage.StorageFolder and the filename as string, but neither of those were usable since the ExternalStorageFile object is not as you might expect a derivative of Windows.Storage.StorageFile, but is instead in the Microsoft.Phone.Storage namespace – hence I had to create a new constructor.

Download the latest version of the wrapper code from http://sqlwinrt.codeplex.com to get this update – note that this is built against SQLite version 3.8.2 – make sure you update to this version using the Visual Studio – Tools – Extensions and Updates wizard.

Download the sample project here

Note that it covers both scenarios covered in this post. At the top of app.xaml.cs there is a compile time symbol #define USE_SDCARD – comment this out to test the ‘database shipped as content’, or leave it in to test the SD card access. You’ll need a real device for the latter and before testing the app use your PC to copy the customers.sqlite file from the project onto the sd card and insert into your phone. Sadly, the emulator does not emulate a removable storage card!

How to massively improve SQLite Performance (using SqlWinRT)

Use ConfigureAwait(false) on calls to SqlWinRT async methods to improve INSERT performance up to 145 times, and SELECT performance up to 80 times 

Sample project: SQLitePerformance.zip

I have been seeing a few comments by people complaining of poor performance when executing SELECT statements against a SQLite database using the SQLWinRT wrapper, or when adding new records using multiple consecutive INSERT statements.

With many relational databases, poor performance on INSERT can often be rectified just by wrapping all your operations within a single transaction. If you don’t explicitly declare a transaction when programming against SQLite, the database engine creates an implicit transaction for each statement execution and that has an overhead associated with it, so by wrapping all your INSERTs inside a single transaction, you would expect a performance boost.

With SELECT operations, poor performance is often just down to not having the correct keys defined. If you have a statement such as SELECT * FROM CUSTOMER WHERE NAME = ‘CONTOSO’ and you execute it on a database where you have not defined a key on the NAME column, the only way the database engine can find the required record is to start at the first record and read sequentially down the table until it reaches the end in order to select the rows to return (called a ‘Table Scan’). If you simply want to select all the records in a table (SELECT * FROM CUSTOMER), then you can’t avoid the Table Scan – in fact that’s what you want – so you would expect that there wasn’t very much you could do to improve performance in that case.

Well – that’s the theory. I set about building a simple demo to demonstrate these points, but it didn’t turn out quite how I expected! It turns out that, important though the points already mentioned are, the most important factor BY FAR is how you call the async methods of the SQLWinRT API! Read on…

The Test Program

For my test program, I was inspired by this post on Stack Overflow: How do I improve the performance of SQLite. That post is quite old and is talking about C++ dev, so not directly relevant to Windows Phone or Windows Store app development using managed code, but I liked the test case, which was to take a large dataset from the City of Toronto’s publically available transportation data. Unfortunately, the exact same dataset used in the original post isn’t available anymore, so I couldn’t do a direct comparison, but they did have the Transportation Trips dataset, containing 128982 records that we can first insert into a SQLite database, and then select them out again.

SQLite Bulk Insert

The dataset is in the form of a CSV text file, representing 128982 rows, each containing 8 columns. The code to read the file and extract the values  looks like this:

SQLiteWinRT.Database db;

private async void Button_Start_Click(object sender, RoutedEventArgs e)
{
    int Route_ID;
    int Service_ID;
    int Trip_ID;
    string Trip_Headsign;
    int Direction_ID;
    int Block_ID;
    int Shape_ID;
    bool Wheelchair_Accessible;

    Button_Start.IsEnabled = false;

    /*********************************************/
    /* Open the Database and create the Schema */
    await LoadDatabase();

    Stopwatch sw = Stopwatch.StartNew();
    int n = 0;

    // Prepare statement
    using (var statement = await db.PrepareStatementAsync(
        @"INSERT INTO TTC (id, Route_ID, Service_ID, Trip_ID, 
                           Trip_Headsign, Direction_ID, Block_ID, 
                           Shape_ID, Wheelchair_Accessible) 
            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)"))
    {
        // Start transaction
        await db.ExecuteStatementAsync("BEGIN TRANSACTION");

        /*********************************************/
        /* Open input file and import into Database*/
        var inputfile = await Windows.ApplicationModel.Package.Current.
            InstalledLocation.GetFileAsync("trips.txt");
        using (var inputStream = await inputfile.OpenSequentialReadAsync())
        {
            using (StreamReader rdr = 
                new StreamReader(inputStream.AsStreamForRead()))
            {
                while (true)
                {
                    string inputline = await rdr.ReadLineAsync();
                    if (inputline == null)
                        break;

                    // Discard line 0 - header line
                    if (n > 0)
                    {
                        string[] fields = inputline.Split(new char[] { ',' });

                        Route_ID = Int32.Parse(fields[0]); ;
                        Service_ID = Int32.Parse(fields[1]);
                        Trip_ID = Int32.Parse(fields[2]);
                        Trip_Headsign = fields[3];
                        Direction_ID = Int32.Parse(fields[4]);
                        Block_ID = Int32.Parse(fields[5]);
                        Shape_ID = Int32.Parse(fields[6]);
                        Wheelchair_Accessible = fields[7] == "1" ? true : false;

                        /* Bind parameter values and Insert */
                        statement.Reset();
                        statement.BindIntParameterAt(1, n);
                        statement.BindIntParameterAt(2, Route_ID);
                        statement.BindIntParameterAt(3, Service_ID);
                        statement.BindIntParameterAt(4, Trip_ID);
                        statement.BindTextParameterAt(5, Trip_Headsign);
                        statement.BindIntParameterAt(6, Direction_ID);
                        statement.BindIntParameterAt(7, Block_ID);
                        statement.BindIntParameterAt(8, Shape_ID);
                        statement.BindIntParameterAt(9, Wheelchair_Accessible ? 1 : 0);

                        await statement.StepAsync();
                    }

                    n++;

                    if (n % 100 == 0)
                    {
                        progressBar.Value = n;
                    }
                }
            }
        }

        // Commit transaction
        await db.ExecuteStatementAsync("COMMIT TRANSACTION");
    }

    db.Dispose();
    db = null;

    var report = String.Format(
        "Inserted {0:d} records in {1:0.00} seconds", 
        n - 1, 
        (double)sw.ElapsedMilliseconds / 1000);
    MessageBox.Show(report);

    Button_Start.IsEnabled = true;
}

private async Task LoadDatabase()
{
    db = new SQLiteWinRT.Database(
        ApplicationData.Current.LocalFolder, "sqliteperf.db");

    await db.OpenAsync();

    string sql = @"
        CREATE TABLE IF NOT EXISTS TTC 
            (id INTEGER PRIMARY KEY, 
                Route_ID INTEGER, 
                Service_ID INTEGER, 
                Trip_ID INTEGER, 
                Trip_Headsign TEXT,
                Direction_ID INTEGER, 
                Block_ID INTEGER, 
                Shape_ID INTEGER, 
                Wheelchair_Accessible BOOL)";

    await db.ExecuteStatementAsync(sql);
}

Using this code, and by commenting out lines here and there as appropriate, we can test three scenarios:

  • Processing the input file but not inserting records in the database (this just gives us the time for the file processing)
  • Uncomment the call to StepAsync() to Insert each record into the database individually
  • Uncomment the lines executing the BEGIN TRANSACTION, END TRANSACTION statements so all records are inserted inside a single transaction

testrunner  Transaction

And the results? Well, not great, to be honest:

Test Total Time (seconds) – 128982 records Insert Time per record (ms)
Process records – no insert 7
Insert records individually 6307 49
Insert records within a containing transaction 3177 25

Although wrapping all the inserts into a single transaction halves the time it takes to insert the 128982 records compared to separate operations (where the database engine will activate an implicit transaction for every insert), we are still only getting 25ms per insert, or 40 operations per second. That’s not too impressive.

Trying ConfigureAwait(false)

Those performance figures are disappointing and make bulk insert operations in a Windows Phone or Windows Store app impractical. However, look what happens when we make a subtle change to the main loop of code:

Stopwatch sw = Stopwatch.StartNew();
int n = 0;

// Prepare statement
using (var statement = await db.PrepareStatementAsync(
    @"INSERT INTO TTC (id, Route_ID, Service_ID, Trip_ID, Trip_Headsign, 
                        Direction_ID, Block_ID, Shape_ID, Wheelchair_Accessible) 
                VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)"))
{
    // Start transaction
    await db.ExecuteStatementAsync("BEGIN TRANSACTION");

    /*********************************************/
    /* Open input file and import into Database*/
    var inputfile = await Windows.ApplicationModel.Package.Current.
        InstalledLocation.GetFileAsync("trips.txt");
    using (var inputStream = await inputfile.OpenSequentialReadAsync())
    {
        using (StreamReader rdr = new StreamReader(inputStream.AsStreamForRead()))
        {
            while (true)
            {
                string inputline = await rdr.ReadLineAsync();
                if (inputline == null)
                    break;

                // Discard line 0 - header line
                if (n > 0)
                {
                    string[] fields = inputline.Split(new char[] { ',' });

                    Route_ID = Int32.Parse(fields[0]); ;
                    Service_ID = Int32.Parse(fields[1]);
                    Trip_ID = Int32.Parse(fields[2]);
                    Trip_Headsign = fields[3];
                    Direction_ID = Int32.Parse(fields[4]);
                    Block_ID = Int32.Parse(fields[5]);
                    Shape_ID = Int32.Parse(fields[6]);
                    Wheelchair_Accessible = fields[7] == "1" ? true : false;

                    /* Bind parameter values and Insert */
                    statement.Reset();
                    statement.BindIntParameterAt(1, n);
                    statement.BindIntParameterAt(2, Route_ID);
                    statement.BindIntParameterAt(3, Service_ID);
                    statement.BindIntParameterAt(4, Trip_ID);
                    statement.BindTextParameterAt(5, Trip_Headsign);
                    statement.BindIntParameterAt(6, Direction_ID);
                    statement.BindIntParameterAt(7, Block_ID);
                    statement.BindIntParameterAt(8, Shape_ID);
                    statement.BindIntParameterAt(9, Wheelchair_Accessible ? 1 : 0);

                    await statement.StepAsync().AsTask().ConfigureAwait(false);
                }

                n++;
                if (n % 100 == 0)
                {
                    Dispatcher.BeginInvoke(()=>progressBar.Value = n);
                }
            }
        }
    }

    // Commit transaction
    await db.ExecuteStatementAsync("COMMIT TRANSACTION");
}

db.Dispose();
db = null;

Dispatcher.BeginInvoke(() =>
    {
        var report = String.Format(
            "Inserted {0:d} records in {1:0.00} seconds", 
            n - 1, (double)sw.ElapsedMilliseconds / 1000);
        MessageBox.Show(report);

        Button_Start.IsEnabled = true;
    });
}

The main – and significant change above – is that the StepAsync() method is now called in a different way:

await statement.StepAsync().AsTask().ConfigureAwait(false);

In addition, the code that ‘touches’ the UI, such as the MessageBox.Show() call, and the code setting the ProgressBar is now called using Dispatcher.BeginInvoke(Action a). This is necessary because the change to how StepAsync() is called has a knock-on effect of causing the code to end up executing on a background thread – I will explain more on this shortly.

What does this do to the timings?:

Test Total Time (seconds) – 128982 records Insert Time per record (ms)
Process records – no insert 7
Insert records individually 6307 49
Insert records within a containing transaction 3206 25
Insert individually with ConfigureAwait(false) 2791 21
Insert within a transaction with ConfigureAwait(false) 55 0.43

TransactionWithConfigureAwait

WHOA! What happened there? If you insert records within a transaction and use ConfigureAwait(false), you can achieve insert performance of one insert every 0.43 ms, or 2345 records per second. Now we’re talking! That means the performance of inserting records individually without using ConfigureAwait(false) is more than 144 times slower than the best case.

Why such a dramatic improvement? Well, the Task.ConfigureAwait(bool continueOnCapturedContext) method is used to configure the awaiter used to await the result of the asynchronous operation. An awaiter is an object you don’t see or program directly as a developer, but simply by using the await keyword when calling an asynchronous method, the compiler will generate code that uses an awaiter to handle the suspension and reactivation of your calling method while it waits for some asynchronous operation to complete. When the asynchronous method has completed, the awaiter resumes execution of your code which by default happens on the same context (think ‘thread’) you were on when you called the async method. But if you set ConfigureAwait(false), it doesn’t do that but instead continues on whatever context the async method executed on. There’s a performance advantage to this, which is why the advice to authors of library code is that you should always make async calls within your library code using ConfigureAwait(false) – the caller of your library method can then make the decision on whether to return to their original context by choosing whether or not to use ConfigureAwait(false) on the call to your async library method.

Which is what we are doing here – by setting ConfigureAwait(false) on our call to SqlWinRT:Statement.StepAsync() we are saying “don’t bother continue on the originating context, stay on whatever context you are executing on”. And as you can see, the performance gain is spectacular! To be honest, I was very surprised just how spectacular the performance improvement is. Normally, you would expect a modest performance gain, but I guess that because this call is happening between managed code and a WinRT component, the overhead of ConfigureAwait(true) – the default – is particularly significant.

One consequence of using ConfigureAwait(false) is that our code after the await call resumes on a background thread, so when we want to interact with the UI, such as to set the ProgressBar or to display the message at the end, we have to use the Dispatcher to make sure the code that touches the UI executes back on the UI thread:

Dispatcher.BeginInvoke(() =>
    {
        var report = String.Format("Inserted {0:d} records in {1:0.00} seconds", 
            n, (double)sw.ElapsedMilliseconds / 1000);
        MessageBox.Show(report);

        Button_Start.IsEnabled = true;
    });

If we don’t do that, you get an exception.

SELECT Performance

What about the performance of reading records out of the database? The warnings I gave in the introduction to this piece about having appropriate keys configured if you are doing a SELECT with a filter on a column that is not the primary key are still valid. But even if you are simply reading all the records out of a table, whether you use ConfigureAwait(false) again has a huge impact.

Here’s the code you would probably write to read all the rows in our table and to load them into in-memory objects in an ObservableCollection<T> ready to display on the UI:

private async void Button_Select_Click(object sender, RoutedEventArgs e)
{
    if (db == null)
    {
        db = new SQLiteWinRT.Database(
            ApplicationData.Current.LocalFolder, "sqliteperf.db");

        await db.OpenAsync();
    }


    Stopwatch sw = Stopwatch.StartNew();
    int n = 0;
    Button_Select.IsEnabled = false;

    string sql = @"
        SELECT
            id , 
                Route_ID , 
                Service_ID, 
                Trip_ID, 
                Trip_Headsign,
                Direction_ID, 
                Block_ID, 
                Shape_ID, 
                Wheelchair_Accessible
            FROM TTC";
    var stmt = await db.PrepareStatementAsync(sql);

    ObservableCollection<TransportationTrip> tripCollection =
        new ObservableCollection<TransportationTrip>();

    while (await stmt.StepAsync())
    {
        var trip = new TransportationTrip()
        {
            ID = stmt.GetIntAt(0),
            RouteID = stmt.GetIntAt(1),
            ServiceID = stmt.GetIntAt(2),
            TripID = stmt.GetIntAt(3),
            TripHeadsign = stmt.GetTextAt(4),
            DirectionID = stmt.GetIntAt(5),
            BlockID = stmt.GetIntAt(6),
            ShapeID = stmt.GetIntAt(7),
            WheelchairAccessible = 
                stmt.GetIntAt(8) == 1 ? true : false,
        };

        tripCollection.Add(trip);
        n++;
    }

    var report = String.Format("Selected {0:d} records in {1:0.00} seconds",
        n, (double)sw.ElapsedMilliseconds / 1000);
    MessageBox.Show(report);

    Button_Select.IsEnabled = true;
}

Running this gives the following result:

SELECT-no-Await

2838 seconds! That sucks – big time.

Then do it again, but make these subtle changes:

while (await stmt.StepAsync().AsTask().ConfigureAwait(false))
{
    var trip = new TransportationTrip()
    {
        ID = stmt.GetIntAt(0),
        RouteID = stmt.GetIntAt(1),
        ServiceID = stmt.GetIntAt(2),
        TripID = stmt.GetIntAt(3),
        TripHeadsign = stmt.GetTextAt(4),
        DirectionID = stmt.GetIntAt(5),
        BlockID = stmt.GetIntAt(6),
        ShapeID = stmt.GetIntAt(7),
        WheelchairAccessible = stmt.GetIntAt(8) == 1 ? true:false,
    };

    tripCollection.Add(trip);
    n++;
}

Dispatcher.BeginInvoke(() =>
    {
        var report = String.Format("Selected {0:d} records in {1:0.00} seconds", 
            n, (double)sw.ElapsedMilliseconds / 1000);
        MessageBox.Show(report);

        Button_Select.IsEnabled = true;
    });

Which gives this result:

SELECT-await

That’s some improvement! Comparing the two:

Test Total Time (seconds) – SELECT 128981 records SELECT Time per record (ms) Records per second
SELECT 2838 22 45
SELECT with ConfigureAwait(false) 32.4 0.25 3980

That’s a huge improvement!

[WARNING: The timings quoted here are for running on the emulator. You should expect times on a real device to be very substantially slower.]

Conclusions

Some golden rules emerge from this:

  1. Use ConfigureAwait(false) when calling SqlWinRT async methods, particularly within repetitive looping such as INSERT or SELECT of a significant number of records. Remember that when you do so, your code will not resume on the same context it started on, so take appropriate measures to handle this.
  2. In addition to using ConfigureAwait(false), wrap large numbers of INSERTs in a single transaction to get the best performance.

The last learning from this is not specific to SqlWinRT: if you call async methods on a WinRT component, there is a significant overhead in switching back to the originating context. Try calling such a component using ConfigureAwait(false) – it may yield significant performance benefits.

Lastly – this was a test program. If you ever find yourself trying to read 128000 records into memory, I would suggest you have another think about your app design and whether you really need all those objects in memory Smile .

SQLiteWinRT: Now BLOB columns and Windows 8.1 supported

I’ve posted some updates to the SQLite WinRT API at http://sqlwinrt.codeplex.com. The SQLite WinRT API offers lightweight Windows Runtime (WinRT) APIs you can use to access the most common SQLite database functionality by using SQL statements, rather than a LINQ-style API.

Support for Windows 8.1

One change is to add an implementation for Windows 8.1. So if you download the source code now (there’s no msi or NUGet package for this as yet), you’ll get three projects which are the WinRT components for Windows 8.0, Windows 8.1 and Windows Phone 8.0. Make sure you have installed the SQLite SDK for your target platform on the Tools – Extensions and Updates menu and then Just include the appropriate project in your own solution, and you’re good to go. See my earlier post for an introduction to programming with the API: http://andywigley.com/2013/06/06/sqlite-winrt-database-programming-on-windows-phone-and-windows-8/

Namespaces Standardised

The other relatively minor change is that I’ve standardised the namespace used to SQLWinRT for all platforms. It just makes it a little easier to share code across platforms that way. That does mean that the blog post referenced in the previous paragraph shows code using the old SQLiteWinRTPhone namespace – though the sample accompanying that post has been updated.

Support for BLOB columns

There is a major update in functionality though – support for BLOB columns, which was requested to help store byte arrays – or Images – directly in the database.

You can define a table in the database with a BLOB column using code similar to this:

// Get a reference to the SQLite database
db = new SQLiteWinRT.Database(ApplicationData.Current.LocalFolder, "sqliteblobdemo.db");

await db.OpenAsync();

string sql = @"
    CREATE TABLE IF NOT EXISTS
        Pictures(Id     INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
                 Name   VARCHAR(140),
                 Image  BLOB);";
await db.ExecuteStatementAsync(sql);

Then, to store a record in this table, you could do something like:

private async void Insert_RecordAsync(string description, BitmapImage image)
{
    string sql = @"INSERT INTO Pictures (Name, Image) VALUES (@name, @image)";
    var db = await App.GetDatabaseAsync();
    using (var statement = await db.PrepareStatementAsync(sql))
    {
        // Convert BitmapImage to byte array
        byte[] imagebytes = ConvertToBytes(image);
        // .. and from that to an IBuffer
        Windows.Storage.Streams.IBuffer imagebuffer = imagebytes.AsBuffer();

        // set the statement parameters
        statement.BindTextParameterWithName("@name", description);
        statement.BindBlobParameterWithName("@image", imagebuffer);

        await statement.StepAsync();
    }
}

private byte[] ConvertToBytes(BitmapImage bitmapImage)
{
    byte[] data = null;
    using (MemoryStream stream = new MemoryStream())
    {
        WriteableBitmap wBitmap = new WriteableBitmap(bitmapImage);
        wBitmap.SaveJpeg(stream, wBitmap.PixelWidth, wBitmap.PixelHeight, 0, 100);
        stream.Seek(0, SeekOrigin.Begin);
        data = stream.GetBuffer();
    }

    return data;
}

Here’s an example to read data out again:

    protected override PictureViewModel CreateItem(SQLiteWinRT.Statement statement)
    {
      // Read the image from the BLOB column
        Windows.Storage.Streams.IBuffer blobBuffer = null;
        if (statement.GetColumnType(2) != ColumnType.Null)
        {
            blobBuffer = statement.GetBlobAt(2);
        }

        // Convert IBuffer back to a BitmapImage
        byte[] pictureBytes = blobBuffer.ToArray();

        var bitmapSource = new BitmapImage();

        using (MemoryStream ms = new MemoryStream(pictureBytes))
        {
            bitmapSource.CreateOptions = BitmapCreateOptions.None;
            ms.Seek(0, SeekOrigin.Begin);
            bitmapSource.SetSource(ms);
        };

      var c = new PictureViewModel(
        statement.GetIntAt(0),
        statement.GetTextAt(1),
        bitmapSource);

      return c;
    }

Here’s a complete sample app you can study to help implement this functionality in your own apps:

Sample code SQLiteBlobSample.zip