WordprocessingDocument.Open is very slow

[amanbolat]

Description

WordprocessingDocument.Open is very very slow when reading big .docx document.
i'm trying to read 10 mb sized .docx document and it takes about 1 minute just to open it.

Information

• .NET Target: .NET Core 2.2
• DocumentFormat.OpenXml Version: 2.9.0

Repro

Console.WriteLine("Creating filter")
using (var doc = WordprocessingDocument.Open(path, false))
{
        Console.WriteLine("Creating BodyReader");
        _bodyReader = OpenXmlReader.Create(doc.MainDocumentPart.Document);
}

Link to the file: https://drive.google.com/file/d/1_InQLbZ19KCUgkuePAiLXvUuLcZl6Qu7/view?usp=sharing

Uploaded to GitHub: 10mb_file.docx

Observed

I put to lines of Console.WriteLine so the time between "Creating filter" and "Creating BodyReader" is about 1 min. It doesn't matter if i opening file from memory stream or just giving it a real path to the file.

Expected

Instant open expected :)

[twsouthwick]

Thanks for the issue. What OS are you running on?

[twsouthwick]

Here's a benchmark version of it:

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using DocumentFormat.OpenXml.Packaging;

namespace OpenSample
{
    [CoreJob]
    public class OpenBenchmark
    {
        [Benchmark]
        public WordprocessingDocument Open()
        {
            var path = ...;
            return WordprocessingDocument.Open(path, false);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var summary = BenchmarkRunner.Run<OpenBenchmark>();
        }
    }
}

And the results:

| Method |    Mean |    Error |   StdDev |
|------- |--------:|---------:|---------:|
|   Open | 21.56 s | 0.3080 s | 0.2730 s |

I agree that seems like a lot of time. I'll look into it.

[amanbolat]

I tried it on windows 10 and MacOS. Results are same.

[amanbolat]

I'm new to C# so i don't know how to profile it and find the problem, but after looking for source code it seems to me that Open function parse all dependencies in file. And this file in my example has a lot of nested charts and images. May be it will help you.

[twsouthwick]

ah that is a good observation. I'll have to see if there's a way to lazily load those (I've never actually explored that scenario)

[twsouthwick]

@amanbolat Sorry for the delay. I've got some time now to look into some of these issues. However, lazily loading this is trickier than I thought. Have you tried loading the package into memory and then accessing it that way? If streaming from disk, it will have some overhead from disk IO. You could try the following:

using(var ms = new MemoryStream())
{
  using(var fs = File.OpenRead("path to file"))
  {
    fs.CopyTo(ms);
  }
  ms.Position(0);

  // Open document from memory stream
}

[amanbolat]

@twsouthwick Hi. Yes, I tried it and result is same, it will take about 1 minute. I tested on my new MacBook with ssd so the overhead shouldn’t be so big, I think so.

[twsouthwick]

Ok. I'll try to make this a higher priority, but to set expectations, I work on this as a side project for work so I'm able to do feature work here somewhat sporadically. If you have any desire to take a stab at it, feel free and I'm happy to provide pointers

[amanbolat]

Thank you.
I’m new to C# but I will try my best.

[ThomasBarnekow]

@amanbolat, try the following method from my CodeSnippets repository:

        public static MemoryStream ReadAllBytesToMemoryStream(string path)
        {
            byte[] buffer = File.ReadAllBytes(path);
            var destStream = new MemoryStream(buffer.Length);
            destStream.Write(buffer, 0, buffer.Length);
            destStream.Seek(0, SeekOrigin.Begin);
            return destStream;
        }

I've benchmarked a number of ways to clone Office Open XML documents and this came out as the fastest.

[amanbolat]

@ThomasBarnekow method doesn't matter. Try to open my file and you will see that it will take about 1 or 2 minutes.

Link to the file: https://drive.google.com/file/d/1_InQLbZ19KCUgkuePAiLXvUuLcZl6Qu7/view?usp=sharing

[github-actions]

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