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CSHARP-4627: Support Union via $unionWith in LINQ3 (#1078)
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‎src/MongoDB.Driver/Linq/IMongoQueryable.cs

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*/
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using System.Linq;
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using MongoDB.Bson.Serialization;
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namespace MongoDB.Driver.Linq
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{

‎src/MongoDB.Driver/Linq/Linq3Implementation/ExtensionMethods/ExpressionExtensions.cs

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* limitations under the License.
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*/
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using System;
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using System.Linq.Expressions;
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using MongoDB.Bson.Serialization;
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namespace MongoDB.Driver.Linq.Linq3Implementation.ExtensionMethods
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{
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internal static class ExpressionExtensions
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{
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public static object Evaluate(this Expression expression)
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{
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if (expression is ConstantExpression constantExpression)
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{
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return constantExpression.Value;
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}
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else
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{
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LambdaExpression lambda = Expression.Lambda(expression);
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Delegate fn = lambda.Compile();
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return fn.DynamicInvoke(null);
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}
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}
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public static (string CollectionName, IBsonSerializer DocumentSerializer) GetCollectionInfo(this Expression innerExpression, Expression containerExpression)
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{
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if (innerExpression is ConstantExpression constantExpression &&

‎src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToExecutableQueryTranslators/ExpressionToExecutableQueryTranslator.cs

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@@ -54,7 +54,7 @@ public static ExecutableQuery<TDocument, TResult> TranslateScalar<TDocument, TRe
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case "AverageAsync":
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return AverageMethodToExecutableQueryTranslator<TResult>.Translate(provider, context, methodCallExpression);
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case "Contains":
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return ContainsMethodToExecutableQueryTranslator.Translate(provider, context, methodCallExpression).AsExecutableQuery<TDocument, TResult>(); ;
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return ContainsMethodToExecutableQueryTranslator.Translate(provider, context, methodCallExpression).AsExecutableQuery<TDocument, TResult>();
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case "Count":
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case "CountAsync":
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return CountMethodToExecutableQueryTranslator.Translate(provider, context, methodCallExpression).AsExecutableQuery<TDocument, TResult>();

‎src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToPipelineTranslators/ExpressionToPipelineTranslator.cs

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return SkipMethodToPipelineTranslator.Translate(context, methodCallExpression);
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case "Take":
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return TakeMethodToPipelineTranslator.Translate(context, methodCallExpression);
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case "Union":
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return UnionMethodToPipelineTranslator.Translate(context, methodCallExpression);
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case "Where":
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return WhereMethodToPipelineTranslator.Translate(context, methodCallExpression);
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}

‎src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToPipelineTranslators/UnionMethodToPipelineTranslator.cs

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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.Expressions;
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using MongoDB.Driver.Linq.Linq3Implementation.Ast;
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using MongoDB.Driver.Linq.Linq3Implementation.Ast.Stages;
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using MongoDB.Driver.Linq.Linq3Implementation.ExtensionMethods;
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using MongoDB.Driver.Linq.Linq3Implementation.Misc;
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using MongoDB.Driver.Linq.Linq3Implementation.Reflection;
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namespace MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToPipelineTranslators
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{
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internal static class UnionMethodToPipelineTranslator
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{
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public static AstPipeline Translate(TranslationContext context, MethodCallExpression expression)
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{
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var method = expression.Method;
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var arguments = expression.Arguments;
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if (method.Is(QueryableMethod.Union))
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{
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var firstExpression = arguments[0];
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var pipeline = ExpressionToPipelineTranslator.Translate(context, firstExpression);
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var secondExpression = arguments[1];
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var secondValue = secondExpression.Evaluate();
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if (secondValue is IMongoQueryable secondQueryable)
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{
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var secondProvider = (IMongoQueryProvider)secondQueryable.Provider;
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var secondCollectionName = secondProvider.CollectionNamespace.CollectionName;
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var secondPipelineInputSerializer = secondProvider.PipelineInputSerializer;
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var secondContext = TranslationContext.Create(secondQueryable.Expression, secondPipelineInputSerializer);
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var secondPipeline = ExpressionToPipelineTranslator.Translate(secondContext, secondQueryable.Expression);
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if (secondPipeline.Stages.Count == 0)
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{
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secondPipeline = null;
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}
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pipeline = pipeline.AddStages(
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pipeline.OutputSerializer,
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AstStage.UnionWith(secondCollectionName, secondPipeline));
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return pipeline;
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}
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throw new ExpressionNotSupportedException(expression, because: "second argument must be IMongoQueryable");
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}
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throw new ExpressionNotSupportedException(expression);
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}
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}
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}

‎tests/MongoDB.Driver.Tests/Linq/Linq3ImplementationTests/Translators/ExpressionToPipelineTranslators/UnionMethodToPipelineTranslatorTests.cs

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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 Xunit;
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namespace MongoDB.Driver.Tests.Linq.Linq3ImplementationTests.Translators.ExpressionToPipelineTranslators
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{
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public class UnionMethodToPipelineTranslatorTests: Linq3IntegrationTest
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{
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private readonly IMongoCollection<Company> _firstCollection;
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private readonly IMongoCollection<Company> _secondCollection;
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public UnionMethodToPipelineTranslatorTests()
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{
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_firstCollection = CreateCollection("clients",
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new Company { Id = 1, Name = "first client" },
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new Company { Id = 2, Name = "second client" },
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new Company { Id = 3, Name = "third client" });
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_secondCollection = CreateCollection("partners",
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new Company { Id = 4, Name = "partner" },
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new Company { Id = 5, Name = "another partner" });
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}
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[Fact]
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public void Union_should_combine_collections()
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{
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var queryable = _firstCollection
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.AsQueryable()
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.Union(_secondCollection.AsQueryable());
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var stages = Translate(_firstCollection, queryable);
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AssertStages(stages, "{ $unionWith : 'partners' }");
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var results = queryable.ToList();
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results.Select(x => x.Id).Should().BeEquivalentTo(new[] { 1, 2, 3, 4, 5 });
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}
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[Fact]
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public void Union_should_combine_collection_with_itself()
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{
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var queryable = _firstCollection
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.AsQueryable()
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.Union(_firstCollection.AsQueryable());
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var stages = Translate(_firstCollection, queryable);
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AssertStages(stages, "{ $unionWith : 'clients' }");
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var results = queryable.ToList();
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results.Select(x => x.Id).Should().BeEquivalentTo(new[] { 1, 2, 3, 1, 2, 3 });
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}
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[Fact]
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public void Union_should_combine_filtered_collections()
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{
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var queryable = _firstCollection
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.AsQueryable()
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.Where(c => c.Name.StartsWith("second"))
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.Union(_secondCollection.AsQueryable().Where(c => c.Name.StartsWith("another")));
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var stages = Translate(_firstCollection, queryable);
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AssertStages(stages,
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"{ $match : { Name : /^second/s } }",
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"{ $unionWith : { coll : 'partners', pipeline : [{ $match : { Name : /^another/s } }] } }");
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var results = queryable.ToList();
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results.Select(x => x.Id).Should().BeEquivalentTo(new[] { 2, 5 });
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}
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[Fact]
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public void Union_should_support_projection()
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{
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var queryable = _firstCollection
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.AsQueryable()
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.Where(c => c.Name.StartsWith("second"))
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.Select(c => new ProjectedCompany { Number = c.Id })
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.Union(_secondCollection.AsQueryable().Select(c => new ProjectedCompany { Number = c.Id }));
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var stages = Translate(_firstCollection, queryable);
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AssertStages(stages,
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"{ $match : { Name : /^second/s } }",
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"{ $project : { Number : '$_id', _id : 0 } }",
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"{ $unionWith : { coll : 'partners', pipeline : [{ $project : { Number : '$_id', _id : 0 } }] } }");
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var results = queryable.ToList();
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results.Select(x => x.Number).Should().BeEquivalentTo(new[] { 2, 4, 5 });
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}
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[Fact]
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public void Union_should_support_projection_to_anonymous()
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{
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var queryable = _firstCollection
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.AsQueryable()
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.Where(c => c.Name.StartsWith("second"))
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.Select(c => new { Number = c.Id })
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.Union(_secondCollection.AsQueryable().Select(c => new { Number = c.Id }));
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var stages = Translate(_firstCollection, queryable);
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AssertStages(stages,
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"{ $match : { Name : /^second/s } }",
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"{ $project : { Number : '$_id', _id : 0 } }",
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"{ $unionWith : { coll : 'partners', pipeline : [{ $project : { Number : '$_id', _id : 0 } }] } }");
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var results = queryable.ToList();
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results.Select(x => x.Number).Should().BeEquivalentTo(new[] { 2, 4, 5 });
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}
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private IMongoCollection<Company> CreateCollection(string collectionName, params Company[] data)
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{
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var collection = GetCollection<Company>(collectionName);
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CreateCollection(collection, data);
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return collection;
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}
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public class Company
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{
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public int Id { get; set; }
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public string Name { get; set; }
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}
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public class ProjectedCompany
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{
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public int Number { get; set; }
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}
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}
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}

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