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Add support for IAsyncEnumerable<T> #903

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thomaslevesque opened this issue Oct 12, 2019 · 12 comments · May be fixed by #4855
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Add support for IAsyncEnumerable<T> #903

thomaslevesque opened this issue Oct 12, 2019 · 12 comments · May be fixed by #4855
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@thomaslevesque
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thomaslevesque commented Oct 12, 2019 •
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Is your feature request related to a problem? Please describe.

The API for enumerating query results isn't great, because it forces the user to be aware of the fact that the results are fetched page by page:

var iterator = ...
while (iterator.HasMoreResults)
{
    var page = await iterator.ReadNextAsync();
    foreach (var item in page)
    {
        ...
    }
}

Describe the solution you'd like

The FeedIterator<T> API is useful, because it gives you more information (e.g. request charge), but in most cases the user just wants the results, so it would be nice to have a higher level abstraction. The IAsyncEnumerable<T> interface seems perfect for this.

There could be an AsAsyncEnumerable extension method like this:

public static async IAsyncEnumerable<T> AsAsyncEnumerable<T>(
    this FeedIterator<T> iterator,
    [EnumeratorCancellation] CancellationToken cancellationToken = default)
{
    while (iterator.HasMoreResults)
    {
        var page = await iterator.ReadNextAsync(cancellationToken);
        foreach (var item in page)
        {
            cancellationToken.ThrowIfCancellationRequested();
            yield return item;
        }
    }
}

The consuming code would be simplified to this:

var iterator = ...
await foreach (var item in iterator.AsAsyncEnumerable())
{
    ...
}

Describe alternatives you've considered
N/A

Additional context

The await foreach feature was introduced in C# 8, so this would only be useful to people already using C# 8.
However, the Microsoft.Bcl.AsyncInterfaces package is compatible with netstandard2.0 and net461, so it wouldn't require running .NET Core 3.
@ealsur ealsur added the VNext Next Major version of SDK label Oct 14, 2019
@ealsur
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ealsur commented Oct 14, 2019

We are working on this at the moment 😄

@thomaslevesque
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Awesome!

@ealsur
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ealsur commented Nov 7, 2019

@thomaslevesque See the V4 (preview) package https://docs.microsoft.com/en-us/azure/cosmos-db/create-sql-api-dotnet-v4#query-the-items

@ealsur ealsur closed this as completed Nov 7, 2019
@thomaslevesque
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Cool, thanks!

@cfindlayvcs
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cfindlayvcs commented Dec 2, 2020 •
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@ealsur , I just tried this with the latest version of the Cosmos DB API (3.15.2) on .NET Core 3.1 and GetItemQueryIterator<> does not return IAsyncEnumerable. I get this:

There is no 4.0 preview package.

image

@lorenpaulsen
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@ealsur , I just tried this with the latest version of the Cosmos DB API (3.15.2) on .NET Core 3.1 and GetItemQueryIterator<> does not return IAsyncEnumerable. I get this:

There is no 4.0 preview package.

image

The 4.0 preview package can be found here: https://www.nuget.org/packages/Azure.Cosmos

@thomaslevesque
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The 4.0 preview package can be found here: https://www.nuget.org/packages/Azure.Cosmos

Indeed. Honestly, I'm not sure how we're supposed to guess that.

  • The README says it's the repo for "Version 3", with no mention of a version 4
  • The README still points to the old package and doesn't mention the new one
  • The old package doesn't mention that it's been superseded by a new one
  • The new package points to this repo, which doesn't seem to know anything about the new package

I think I discovered the new package by accident in an article. There's almost no chance a new user will find it if they end up on this repo.

@paulirwin
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Is there an anticipated release date for the v4 SDK? It looks like the last preview came out almost a year and a half ago. Thanks for any updates!

@Socolin
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Socolin commented Jan 25, 2022

Hello, is there any ETA for this ? It look like the v4 is abandon since 2 year, is there any reason for this ?

@bartelink
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See #2976

@dersia
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dersia commented Jun 13, 2023 •
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as of the comment #2976 (comment) I'd like to ask to reopen this issue. a feature like this needs to in the sdk, if it's not v4, then in v3, but this is very much needed.

Maybe @jcocchi can help with this?

@onionhammer
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Any movement on this?

This was referenced Mar 18, 2024
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@seesharprun seesharprun mentioned this issue Oct 25, 2024
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Query: Adds asynchronous enumeration seesharprun/azure-cosmos-dotnet-v3
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@bartelink @Socolin @onionhammer @dersia @ealsur @thomaslevesque @paulirwin @lorenpaulsen @cfindlayvcs