Async query enumeration and cancellation support for long running queries #423
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KenitoInc
requested review from
corranrogue9,
KenitoInc,
ElizabethOkerio,
gathogojr,
habbes and
odero
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@KenitoInc Is there anything I can to to speed up the review? |
| @@ -115,7 +116,7 @@ await WriteObjectInlineAsync(graph, resourceSetType, writer, writeContext) | |||
| IEdmStructuredTypeReference elementType = GetResourceType(resourceSetType); | |||
| ODataResourceSet resourceSet = CreateResourceSet(enumerable, resourceSetType.AsCollection(), writeContext); | |||
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| Func<object, Uri> nextLinkGenerator = GetNextLinkGenerator(resourceSet, enumerable, writeContext); | |||
| Func<Func<object, Uri>> nextLinkGenerator = () => GetNextLinkGenerator(resourceSet, enumerable, writeContext); | |||
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I do not follow the need for the extra Func. Can you help me understand?
| resourceSet.NextPageLink = originalNexPageLink; | ||
| } | ||
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| resourceSet.NextPageLink = nextLinkGenerator()(lastResource); |
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This might be related to my other question about nextLinkGenerator, but doesn't calling this after setting the original mean that a new link is not generated?
| @@ -25,5 +26,8 @@ public interface ITruncatedCollection : IEnumerable | |||
| /// Gets a value representing if the collection is truncated or not. | |||
| /// </summary> | |||
| bool IsTruncated { get; } | |||
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| bool IsAsyncEnumerationPossible { get; } | |||
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I believe that these will be breaking changes for any current implementers of this interface
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| namespace Microsoft.AspNetCore.OData.Query.Container | ||
| { | ||
| /// <summary> | ||
| /// Represents a class that truncates a collection to a given page size. | ||
| /// </summary> | ||
| /// <typeparam name="T">The collection element type.</typeparam> | ||
| public class TruncatedCollection<T> : List<T>, ITruncatedCollection, IEnumerable<T>, ICountOptionCollection |
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Despite that I agree we should remove List<T>, this is certainly a breaking change.
| // the enumerable version just enumerates and is inefficient. | ||
| public TruncatedCollection(IQueryable<T> source, int pageSize, long? totalCount, bool parameterize) | ||
| : base(pageSize > 0 ? Take(source, pageSize, parameterize) : source) | ||
| public bool IsAsyncEnumerationPossible => _items is IAsyncEnumerable<T>; |
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I think this is trying to follow the same pattern as truncation? I don't think I agree with either approach, and I'm not sure we should be adding more precedence for this type of pattern. I probably have more feedback about this class, but I think getting the design correct first is important.
| { | ||
| MethodInfo genericMethod = _limitResultsGenericMethod.MakeGenericMethod(queryable.ElementType); | ||
| object[] args = new object[] { queryable, limit, parameterize, null }; | ||
| IQueryable results = genericMethod.Invoke(null, args) as IQueryable; | ||
| resultsLimited = (bool)args[3]; | ||
| resultsLimited = (Func<bool>)args[3]; |
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I don't get it. parameterize is not a reference or anything, it always has whatever value was passed into LimitResults, doesn't it?
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This logic bubbles up I think all the way up to the change of pageSize to a delegate
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Also, there seems to be a lack of test coverage in general, or there is something critical that I've missed about why these delegates exist, because (Func<bool>)((object)false) I believe will throw InvalidCastException
| @@ -134,6 +134,8 @@ public void CreatePropertyContainer_PageSize() | |||
| PropertyContainer container = ToContainer(containerExpression); | |||
| var result = container.ToDictionary(new IdentityPropertyMapper())["PropertyName"]; | |||
| var truncatedCollection = Assert.IsType<TruncatedCollection<int>>(result); | |||
| // Enumerate the list so that the PageSize gets initialized. | |||
| truncatedCollection.ToList(); | |||
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What happens if we don't enumerate the sequence? Requiring enumeration to get PageSize is a breaking change, I think
| using Xunit; | ||
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| namespace Microsoft.AspNetCore.OData.Tests.Query.Container | ||
| { | ||
| public class TruncatedCollectionTest | ||
| { | ||
| [Fact] |
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If I understand correctly, these tests are being removed because the constructors were removed. TruncatedCollection is public, we can't just remove public constructors
| @@ -794,12 +794,14 @@ public void LimitResults_LimitsResults(int limit, bool resultsLimitedExpected) | |||
| ODataQueryContext context = new ODataQueryContext(model, typeof(Customer)); | |||
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I don't actually see any tests for the new functionality, can you please add them?
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Thanks for the review @corranrogue9. I'm a little swamped right now but will get back to this ASAP. |
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@henning-krause hoping you'd be able to complete this sometime! Would be cool if cancellation token is going to be supported. |
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@henning-krause any chance? |
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@SymbioticKilla Unfortunately, I won't have time for this in the foreseeable future. |
Note: I've reopened this PR since the target branch name changes to main. The original PR can be found here: #324 and was already approved by @corranrogue9.
A long time ago I created an issue to properly cancel long running queries (when the HttpContext.RequestAborted cancellation token is triggered) for the 7.9 version of this code. This was never solved, I think mainly because most of the code is still synchronous.
Now that I moved on to AspNetCoreOData I'm facing the same problem and gave it another shot.
@xuzhg I know that this PR is far from complete. But I wanted to get an opinion from you if I'm moving in the right direction with this and if you would approve this PR once it's complete before I put more effort in this.
For now, I have mainly redesigned the TruncatedCollection to properly support async enumeration (and remove the buffering of the whole response along with this change) as well as the ODataResourceSetSerializer.
So, for paged queries, this approach works.