Oren Eini

CEO of RavenDB

a NoSQL Open Source Document Database

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Couchbase vs RavenDB Performance at Rakuten Kobo Whitepaper

Riddle me thisFile access & Multi threading
time to read 1 min | 178 words
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What would be the output of the following code?

var list = new List<Task>();

var fileStream = File.Open("test", FileMode.Create, FileAccess.ReadWrite, FileShare.None);
for (int i = 0; i < 150; i++)
{
    var index = i;
    var task = Task.Factory.StartNew(() =>
    {
        var buffer = Encoding.ASCII.GetBytes(index + "\r\n");
        fileStream.Write(buffer, 0, buffer.Length);
    });
    list.Add(task);
}


Task.WaitAll(list.ToArray());
fileStream.Flush(true);
fileStream.Dispose();

Please note that:

  • What order the data is saved is not important.
  • Preventing data corruption is important.

Can you guess?

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Riddle me thisString outputs
time to read 1 min | 108 words
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What would be the result of this?

public string Wrap(string x, string y)
{
   return "[" + x ?? y + "]";
}

Can you see the bug?

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Riddle me thisHard links & file moves
time to read 1 min | 200 words
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What would you expect the following code to output?

File.WriteAllText("a","1");
DirectoryBackup.CreateHardLink("b", "a", IntPtr.Zero);
File.WriteAllText("a","2");
if(File.Exists("c"))
    File.Delete("c");
File.Move("b","c");
File.WriteAllText("a", "3");
Console.WriteLine(File.ReadAllText("c"));

CreateHardLink is:

[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
static extern bool CreateHardLink(string lpFileName, string lpExistingFileName, IntPtr lpSecurityAttributes);
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FUTURE POSTS

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