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Reuse a single-result subquery across its projected members (#38502)
Fixes #7776
1 parent f2f2673 commit 347acfc

5 files changed

Lines changed: 225 additions & 3 deletions

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‎src/EFCore/Query/Internal/NavigationExpandingExpressionVisitor.SingleResultSubqueryLifting.cs‎

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// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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namespace Microsoft.EntityFrameworkCore.Query.Internal;
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public partial class NavigationExpandingExpressionVisitor
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{
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private NavigationExpansionExpression LiftSingleResultSubqueries(NavigationExpansionExpression source)
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{
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var selectorBody = source.PendingSelector;
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var collector = new SingleResultMemberAccessCollector();
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collector.Visit(selectorBody);
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foreach (var subquery in collector.Liftable)
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{
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var collection = BuildSingleResultCollection(subquery);
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var innerParameter = Expression.Parameter(collection.Type.GetSequenceType(), "e");
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var rewrittenBody = new ReplacingExpressionVisitor([subquery], [innerParameter]).Visit(selectorBody);
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// The collection already references the outer element via source.PendingSelector; this parameter is unused.
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source = ProcessSelectMany(
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source,
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Expression.Lambda(collection, Expression.Parameter(source.SourceElementType, "o")),
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Expression.Lambda(rewrittenBody, Expression.Parameter(source.SourceElementType, "o"), innerParameter));
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selectorBody = source.PendingSelector;
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}
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return source;
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}
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private static Expression BuildSingleResultCollection(MethodCallExpression subqueryMethod)
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{
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var method = subqueryMethod.Method.GetGenericMethodDefinition();
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var source = subqueryMethod.Arguments[0];
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var elementType = source.Type.GetSequenceType();
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Expression Where(Expression c)
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=> Expression.Call(QueryableMethods.Where.MakeGenericMethod(elementType), c, subqueryMethod.Arguments[1]);
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Expression Skip(Expression c)
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=> Expression.Call(QueryableMethods.Skip.MakeGenericMethod(elementType), c, subqueryMethod.Arguments[1]);
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Expression Reverse(Expression c)
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=> Expression.Call(QueryableMethods.Reverse.MakeGenericMethod(elementType), c);
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var oneRow = method switch
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{
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_ when method == QueryableMethods.FirstWithPredicate || method == QueryableMethods.FirstOrDefaultWithPredicate
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|| method == QueryableMethods.SingleWithPredicate || method == QueryableMethods.SingleOrDefaultWithPredicate
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=> Where(source),
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_ when method == QueryableMethods.LastWithPredicate || method == QueryableMethods.LastOrDefaultWithPredicate
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=> Reverse(Where(source)),
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_ when method == QueryableMethods.LastWithoutPredicate || method == QueryableMethods.LastOrDefaultWithoutPredicate
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=> Reverse(source),
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_ when method == QueryableMethods.ElementAt || method == QueryableMethods.ElementAtOrDefault
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=> Skip(source),
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_ => source
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};
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var firstRow = Expression.Call(QueryableMethods.Take.MakeGenericMethod(elementType), oneRow, Expression.Constant(1));
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return Expression.Call(QueryableMethods.DefaultIfEmptyWithoutArgument.MakeGenericMethod(elementType), firstRow);
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}
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private sealed class SingleResultMemberAccessCollector : ExpressionVisitor
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{
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private static readonly HashSet<MethodInfo> SingleResultMethods =
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[
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QueryableMethods.FirstWithPredicate, QueryableMethods.FirstWithoutPredicate,
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QueryableMethods.FirstOrDefaultWithPredicate, QueryableMethods.FirstOrDefaultWithoutPredicate,
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QueryableMethods.SingleWithPredicate, QueryableMethods.SingleWithoutPredicate,
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QueryableMethods.SingleOrDefaultWithPredicate, QueryableMethods.SingleOrDefaultWithoutPredicate,
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QueryableMethods.LastWithPredicate, QueryableMethods.LastWithoutPredicate,
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QueryableMethods.LastOrDefaultWithPredicate, QueryableMethods.LastOrDefaultWithoutPredicate,
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QueryableMethods.ElementAt, QueryableMethods.ElementAtOrDefault
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];
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private readonly Dictionary<MethodCallExpression, int> _memberAccessCount = new(ReferenceEqualityComparer.Instance);
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public IEnumerable<MethodCallExpression> Liftable
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=> _memberAccessCount.Where(e => e.Value > 1).Select(e => e.Key);
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protected override Expression VisitMember(MemberExpression memberExpression)
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{
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if (memberExpression.Expression is MethodCallExpression { Method.IsGenericMethod: true } subquery
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&& SingleResultMethods.Contains(subquery.Method.GetGenericMethodDefinition()))
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{
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if (_memberAccessCount.TryGetValue(subquery, out var count))
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{
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_memberAccessCount[subquery] = count + 1;
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}
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else
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{
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// First encounter: count it and visit its arguments once (a later access duplicates the count)
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_memberAccessCount[subquery] = 1;
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foreach (var argument in subquery.Arguments)
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{
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Visit(argument);
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}
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}
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return memberExpression;
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}
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return base.VisitMember(memberExpression);
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}
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}
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}

‎src/EFCore/Query/Internal/NavigationExpandingExpressionVisitor.cs‎

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -671,9 +671,10 @@ when QueryableMethods.IsSumWithSelector(method):
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case nameof(Queryable.Select)
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when genericMethod == QueryableMethods.Select:
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return ProcessSelect(
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source,
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methodCallExpression.Arguments[1].UnwrapLambdaFromQuote());
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return LiftSingleResultSubqueries(
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ProcessSelect(
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source,
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methodCallExpression.Arguments[1].UnwrapLambdaFromQuote()));
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678679
case nameof(Queryable.Where)
679680
when genericMethod == QueryableMethods.Where:

‎test/EFCore.Cosmos.FunctionalTests/Query/NorthwindSelectQueryCosmosTest.cs‎

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Original file line numberDiff line numberDiff line change
@@ -695,6 +695,13 @@ public override async Task Projection_in_a_subquery_should_be_liftable(bool asyn
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public override Task Projection_containing_DateTime_subtraction(bool async)
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=> Assert.ThrowsAsync<InvalidOperationException>(() => base.Projection_containing_DateTime_subtraction(async));
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public override async Task Multiple_members_of_correlated_single_result_subquery_lift_to_single_join(bool async, string method)
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{
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await AssertTranslationFailed(() => base.Multiple_members_of_correlated_single_result_subquery_lift_to_single_join(async, method));
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AssertSql();
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}
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public override async Task Project_single_element_from_collection_with_OrderBy_Take_and_FirstOrDefault(bool async)
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{
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// Cosmos client evaluation. Issue #17246.

‎test/EFCore.Specification.Tests/Query/NorthwindSelectQueryTestBase.cs‎

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Original file line numberDiff line numberDiff line change
@@ -2303,4 +2303,55 @@ from o2 in ss.Set<Order>()
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}).Take(5),
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assertOrder: true,
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elementAsserter: (e, a) => AssertCollection(e.OrderIds, a.OrderIds, elementSorter: ee => ee));
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public static TheoryData<bool, string> SingleResultMethodData()
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=> new(
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from async in new[] { true, false }
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from method in new[]
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{
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nameof(Queryable.First), nameof(Queryable.FirstOrDefault),
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nameof(Queryable.Single), nameof(Queryable.SingleOrDefault),
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nameof(Queryable.Last), nameof(Queryable.LastOrDefault),
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nameof(Queryable.ElementAt), nameof(Queryable.ElementAtOrDefault)
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}
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select (async, method));
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[Theory, MemberData(nameof(SingleResultMethodData))]
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public virtual Task Multiple_members_of_correlated_single_result_subquery_lift_to_single_join(bool async, string method)
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=> AssertQuery(
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async,
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ss =>
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{
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var customers = ss.Set<Customer>();
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var orders = ss.Set<Order>().Where(o => o.CustomerID != null);
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return method switch
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{
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nameof(Queryable.First) => from o in orders
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let c = customers.First(c => c.CustomerID == o.CustomerID)
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select new { o.OrderID, c.City, c.Country, c.ContactName },
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nameof(Queryable.FirstOrDefault) => from o in orders
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let c = customers.FirstOrDefault(c => c.CustomerID == o.CustomerID)
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select new { o.OrderID, c.City, c.Country, c.ContactName },
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nameof(Queryable.Single) => from o in orders
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let c = customers.Single(c => c.CustomerID == o.CustomerID)
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select new { o.OrderID, c.City, c.Country, c.ContactName },
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nameof(Queryable.SingleOrDefault) => from o in orders
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let c = customers.SingleOrDefault(c => c.CustomerID == o.CustomerID)
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select new { o.OrderID, c.City, c.Country, c.ContactName },
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nameof(Queryable.Last) => from o in orders
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let c = customers.OrderBy(c => c.CustomerID).Last(c => c.CustomerID == o.CustomerID)
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select new { o.OrderID, c.City, c.Country, c.ContactName },
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nameof(Queryable.LastOrDefault) => from o in orders
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let c = customers.OrderBy(c => c.CustomerID).LastOrDefault(c => c.CustomerID == o.CustomerID)
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select new { o.OrderID, c.City, c.Country, c.ContactName },
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nameof(Queryable.ElementAt) => from o in orders
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let c = customers.Where(c => c.CustomerID == o.CustomerID).OrderBy(c => c.CustomerID).ElementAt(0)
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select new { o.OrderID, c.City, c.Country, c.ContactName },
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nameof(Queryable.ElementAtOrDefault) => from o in orders
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let c = customers.Where(c => c.CustomerID == o.CustomerID).OrderBy(c => c.CustomerID).ElementAtOrDefault(0)
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select new { o.OrderID, c.City, c.Country, c.ContactName },
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_ => throw new InvalidOperationException(method)
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};
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},
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elementSorter: e => e.OrderID);
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}

‎test/EFCore.SqlServer.FunctionalTests/Query/NorthwindSelectQuerySqlServerTest.cs‎

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Original file line numberDiff line numberDiff line change
@@ -2911,6 +2911,61 @@ ORDER BY [c0].[CustomerID]
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""");
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}
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public override async Task Multiple_members_of_correlated_single_result_subquery_lift_to_single_join(bool async, string method)
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{
2916+
await base.Multiple_members_of_correlated_single_result_subquery_lift_to_single_join(async, method);
2917+
2918+
AssertSql(
2919+
method switch
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{
2921+
nameof(Queryable.First) or
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nameof(Queryable.FirstOrDefault) or
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nameof(Queryable.Single) or
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nameof(Queryable.SingleOrDefault) => """
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SELECT [o].[OrderID], [c1].[City], [c1].[Country], [c1].[ContactName]
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FROM [Orders] AS [o]
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LEFT JOIN (
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SELECT [c0].[City], [c0].[ContactName], [c0].[Country], [c0].[CustomerID0]
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FROM (
2930+
SELECT [c].[City], [c].[ContactName], [c].[Country], [c].[CustomerID] AS [CustomerID0], ROW_NUMBER() OVER(PARTITION BY [c].[CustomerID] ORDER BY [c].[CustomerID]) AS [row]
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FROM [Customers] AS [c]
2932+
) AS [c0]
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WHERE [c0].[row] <= 1
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) AS [c1] ON [o].[CustomerID] = [c1].[CustomerID0]
2935+
WHERE [o].[CustomerID] IS NOT NULL
2936+
""",
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nameof(Queryable.Last) or
2938+
nameof(Queryable.LastOrDefault) => """
2939+
SELECT [o].[OrderID], [c1].[City], [c1].[Country], [c1].[ContactName]
2940+
FROM [Orders] AS [o]
2941+
LEFT JOIN (
2942+
SELECT [c0].[City], [c0].[ContactName], [c0].[Country], [c0].[CustomerID0]
2943+
FROM (
2944+
SELECT [c].[City], [c].[ContactName], [c].[Country], [c].[CustomerID] AS [CustomerID0], ROW_NUMBER() OVER(PARTITION BY [c].[CustomerID] ORDER BY [c].[CustomerID] DESC) AS [row]
2945+
FROM [Customers] AS [c]
2946+
) AS [c0]
2947+
WHERE [c0].[row] <= 1
2948+
) AS [c1] ON [o].[CustomerID] = [c1].[CustomerID0]
2949+
WHERE [o].[CustomerID] IS NOT NULL
2950+
""",
2951+
nameof(Queryable.ElementAt) or
2952+
nameof(Queryable.ElementAtOrDefault) => """
2953+
SELECT [o].[OrderID], [c1].[City], [c1].[Country], [c1].[ContactName]
2954+
FROM [Orders] AS [o]
2955+
LEFT JOIN (
2956+
SELECT [c0].[City], [c0].[ContactName], [c0].[Country], [c0].[CustomerID0]
2957+
FROM (
2958+
SELECT [c].[City], [c].[ContactName], [c].[Country], [c].[CustomerID] AS [CustomerID0], ROW_NUMBER() OVER(PARTITION BY [c].[CustomerID] ORDER BY [c].[CustomerID]) AS [row]
2959+
FROM [Customers] AS [c]
2960+
) AS [c0]
2961+
WHERE 0 < [c0].[row] AND [c0].[row] <= 1
2962+
) AS [c1] ON [o].[CustomerID] = [c1].[CustomerID0]
2963+
WHERE [o].[CustomerID] IS NOT NULL
2964+
""",
2965+
_ => throw new InvalidOperationException(method)
2966+
});
2967+
}
2968+
29142969
private void AssertSql(params string[] expected)
29152970
=> Fixture.TestSqlLoggerFactory.AssertBaseline(expected);
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