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CSHARP-2348: Switch to $expr when $elemMatch filter is not supported by server.
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3 files changed

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‎src/MongoDB.Driver/Linq/Linq3Implementation/Ast/Filters/AstFilter.cs

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@@ -13,6 +13,7 @@
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* limitations under the License.
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*/
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using MongoDB.Bson;
@@ -92,7 +93,30 @@ public static AstFieldOperationFilter Compare(AstFilterField field, AstCompariso
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public static AstFieldOperationFilter ElemMatch(AstFilterField field, AstFilter filter)
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{
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if (!ServerSupportsElemMatchFilter(filter))
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{
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throw new ExpressionNotSupportedException($"$elemMatch does not support filter: {filter}");
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}
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return new AstFieldOperationFilter(field, new AstElemMatchFilterOperation(filter));
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static bool ServerSupportsElemMatchFilter(AstFilter filter)
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{
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if (filter is AstOrFilter orFilter &&
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orFilter.Filters.Any(IsImpliedElementFilter))
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{
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return false;
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}
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// TODO: add detection of other unsupported filters as we discover them
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return true;
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static bool IsImpliedElementFilter(AstFilter filter)
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=>
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filter is AstFieldOperationFilter fieldOperationFilter &&
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fieldOperationFilter.Field.Path == "@<elem>";
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}
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}
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public static AstFieldOperationFilter Eq(AstFilterField field, BsonValue value)

‎src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToFilterTranslators/MethodTranslators/AllOrAnyMethodToFilterTranslator.cs

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@@ -72,12 +72,30 @@ public static AstFilter Translate(TranslationContext context, MethodCallExpressi
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}
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else
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{
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// { $elemMatch : { $or : [{ $eq : x }, { $eq : y }, ... ] } } => { $in : [x, y, ...] }
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if (filter is AstOrFilter orFilter &&
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orFilter.Filters.All(IsImpliedElementEqualityComparison))
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{
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var values = orFilter.Filters
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.Select(filter => ((AstFieldOperationFilter)filter).Operation)
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.Select(operation => ((AstComparisonFilterOperation)operation).Value);
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return AstFilter.In(field, values);
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}
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return AstFilter.ElemMatch(field, filter);
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}
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}
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}
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throw new ExpressionNotSupportedException(expression);
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static bool IsImpliedElementEqualityComparison(AstFilter filter)
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=>
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filter is AstFieldOperationFilter fieldOperationFilter &&
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fieldOperationFilter.Field.Path == "@<elem>" &&
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fieldOperationFilter.Operation is AstComparisonFilterOperation comparisonFilterOperation &&
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comparisonFilterOperation.Operator == AstComparisonFilterOperator.Eq;
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}
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}
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‎tests/MongoDB.Driver.Tests/Linq/Linq3Implementation/Jira/CSharp2348Tests.cs

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@@ -0,0 +1,125 @@
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/* Copyright 2010-present MongoDB Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System.Linq;
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using FluentAssertions;
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using MongoDB.Driver.Linq;
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using MongoDB.Driver.Tests.Linq.Linq3Implementation;
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using MongoDB.TestHelpers.XunitExtensions;
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using Xunit;
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namespace MongoDB.Driver.Tests.Linq.Linq3ImplementationTests.Jira
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{
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public class CSharp2348Tests : Linq3IntegrationTest
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{
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[Theory]
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[ParameterAttributeData]
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public void Any_with_equals_should_work(
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[Values(LinqProvider.V2, LinqProvider.V3)] LinqProvider linqProvider)
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{
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var collection = CreateCollection(linqProvider);
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var find = collection.Find(x => x.A.Any(v => v == 2));
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var renderedFilter = TranslateFindFilter(collection, find);
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if (linqProvider == LinqProvider.V2)
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{
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renderedFilter.Should().Be("{ A : { $elemMatch : { $eq : 2 } } }"); // LINQ2 translation is not as simple as it could be but is correct
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}
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else
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{
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renderedFilter.Should().Be("{ A : 2 }");
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}
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var results = find.ToList().OrderBy(x => x.Id).ToList();
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results.Select(x => x.Id).Should().Equal(2);
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}
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[Theory]
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[ParameterAttributeData]
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public void Any_with_or_of_equals_should_work(
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[Values(LinqProvider.V2, LinqProvider.V3)] LinqProvider linqProvider)
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{
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var collection = CreateCollection(linqProvider);
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var find = collection.Find(x => x.A.Any(v => v == 2 || v == 3));
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var renderedFilter = TranslateFindFilter(collection, find);
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var results = find.ToList().OrderBy(x => x.Id).ToList();
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if (linqProvider == LinqProvider.V2)
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{
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renderedFilter.Should().Be("{ A : { $elemMatch : { $or : [{ '' : 2 }, { '' : 3 }] } } }"); // LINQ2 translation is wrong
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results.Should().BeEmpty(); // LINQ2 result is wrong
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}
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else
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{
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renderedFilter.Should().Be("{ A : { $in : [2, 3] } }");
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results.Select(x => x.Id).Should().Equal(2, 3);
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}
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}
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[Theory]
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[ParameterAttributeData]
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public void Any_with_or_of_equals_and_greater_than_should_work(
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[Values(LinqProvider.V2, LinqProvider.V3)] LinqProvider linqProvider)
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{
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var collection = CreateCollection(linqProvider);
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var find = collection.Find(x => x.A.Any(v => v == 2 || v > 3));
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var renderedFilter = TranslateFindFilter(collection, find);
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var results = find.ToList().OrderBy(x => x.Id).ToList();
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if (linqProvider == LinqProvider.V2)
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{
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renderedFilter.Should().Be("{ A : { $elemMatch : { $or : [{ '' : 2 }, { '' : { $gt : 3 } }] } } }"); // LINQ2 translation is wrong
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results.Should().BeEmpty(); // LINQ2 result is wrong
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}
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else
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{
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// the ideal translation would be { Roles : { $elemMatch : { $or : [{ $eq : 2 }, { $gt : 3 }] } } }
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// but the server does not support implied element names in combination with $or
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// see: https://jira.mongodb.org/browse/SERVER-93020
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renderedFilter.Should().Be("{ $expr : { $anyElementTrue : { $map : { input : '$A', as : 'v', in : { $or : [{ $eq : ['$$v', 2] }, { $gt : ['$$v', 3] }] } } } } }");
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results.Select(x => x.Id).Should().Equal(2, 4);
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}
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}
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private IMongoCollection<User> CreateCollection(LinqProvider linqProvider)
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{
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var collection = GetCollection<User>("test", linqProvider);
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CreateCollection(
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collection,
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new User { Id = 1, A = new[] { 1 } },
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new User { Id = 2, A = new[] { 1, 2 } },
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new User { Id = 3, A = new[] { 1, 3 } },
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new User { Id = 4, A = new[] { 1, 4 } });
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return collection;
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}
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public class User
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{
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public int Id { get; set; }
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public int[] A { get; set; }
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}
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public enum Role
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{
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Admin = 1,
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Editor = 2
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}
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}
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}

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