dotnet · smitpatel · Apr 28, 2020 · Apr 23, 2020
diff --git a/...e.Cosmos/Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.QueryingEnumerable.cs b/...e.Cosmos/Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.QueryingEnumerable.cs
@@ -33,6 +33,7 @@ private sealed class QueryingEnumerable<T> : IEnumerable<T>, IAsyncEnumerable<T>
             private readonly Type _contextType;
             private readonly string _partitionKey;
             private readonly IDiagnosticsLogger<DbLoggerCategory.Query> _logger;
+            private readonly bool _performIdentityResolution;
 
             public QueryingEnumerable(
                 CosmosQueryContext cosmosQueryContext,
@@ -42,7 +43,8 @@ public QueryingEnumerable(
                 Func<CosmosQueryContext, JObject, T> shaper,
                 Type contextType,
                 string partitionKeyFromExtension,
-                IDiagnosticsLogger<DbLoggerCategory.Query> logger)
+                IDiagnosticsLogger<DbLoggerCategory.Query> logger,
+                bool performIdentityResolution)
             {
                 _cosmosQueryContext = cosmosQueryContext;
                 _sqlExpressionFactory = sqlExpressionFactory;
@@ -51,17 +53,17 @@ public QueryingEnumerable(
                 _shaper = shaper;
                 _contextType = contextType;
                 _logger = logger;
+                _performIdentityResolution = performIdentityResolution;
 
                 var partitionKey = selectExpression.GetPartitionKey(cosmosQueryContext.ParameterValues);
-
                 if (partitionKey != null && partitionKeyFromExtension != null && partitionKeyFromExtension != partitionKey)
                 {
                     throw new InvalidOperationException(CosmosStrings.PartitionKeyMismatch(partitionKeyFromExtension, partitionKey));
                 }
 
                 _partitionKey = partitionKey ?? partitionKeyFromExtension;
             }
-            
+
             public IAsyncEnumerator<T> GetAsyncEnumerator(CancellationToken cancellationToken = default)
                 => new AsyncEnumerator(this, cancellationToken);
 
@@ -107,6 +109,7 @@ private sealed class Enumerator : IEnumerator<T>
                 private readonly Type _contextType;
                 private readonly string _partitionKey;
                 private readonly IDiagnosticsLogger<DbLoggerCategory.Query> _logger;
+                private readonly bool _performIdentityResolution;
 
                 private IEnumerator<JObject> _enumerator;
 
@@ -119,6 +122,7 @@ public Enumerator(QueryingEnumerable<T> queryingEnumerable)
                     _contextType = queryingEnumerable._contextType;
                     _partitionKey = queryingEnumerable._partitionKey;
                     _logger = queryingEnumerable._logger;
+                    _performIdentityResolution = queryingEnumerable._performIdentityResolution;
                 }
 
                 public T Current { get; private set; }
@@ -141,6 +145,7 @@ public bool MoveNext()
                                         _partitionKey,
                                         sqlQuery)
                                     .GetEnumerator();
+                                _cosmosQueryContext.InitializeStateManager(_performIdentityResolution);
                             }
 
                             var hasNext = _enumerator.MoveNext();
@@ -179,6 +184,7 @@ private sealed class AsyncEnumerator : IAsyncEnumerator<T>
                 private readonly Type _contextType;
                 private readonly string _partitionKey;
                 private readonly IDiagnosticsLogger<DbLoggerCategory.Query> _logger;
+                private readonly bool _performIdentityResolution;
                 private readonly CancellationToken _cancellationToken;
 
                 private IAsyncEnumerator<JObject> _enumerator;
@@ -192,6 +198,7 @@ public AsyncEnumerator(QueryingEnumerable<T> queryingEnumerable, CancellationTok
                     _contextType = queryingEnumerable._contextType;
                     _partitionKey = queryingEnumerable._partitionKey;
                     _logger = queryingEnumerable._logger;
+                    _performIdentityResolution = queryingEnumerable._performIdentityResolution;
                     _cancellationToken = cancellationToken;
                 }
 
@@ -213,6 +220,7 @@ public async ValueTask<bool> MoveNextAsync()
                                         _partitionKey,
                                         sqlQuery)
                                     .GetAsyncEnumerator(_cancellationToken);
+                                _cosmosQueryContext.InitializeStateManager(_performIdentityResolution);
                             }
 
                             var hasNext = await _enumerator.MoveNextAsync();

diff --git a/.../Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.ReadItemQueryingEnumerable.cs b/.../Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.ReadItemQueryingEnumerable.cs
@@ -12,6 +12,7 @@
 using Microsoft.EntityFrameworkCore.Cosmos.Internal;
 using Microsoft.EntityFrameworkCore.Cosmos.Storage.Internal;
 using Microsoft.EntityFrameworkCore.Diagnostics;
+using Microsoft.EntityFrameworkCore.Internal;
 using Microsoft.EntityFrameworkCore.Metadata;
 using Microsoft.EntityFrameworkCore.Metadata.Conventions;
 using Microsoft.EntityFrameworkCore.Query;
@@ -34,19 +35,22 @@ private sealed class ReadItemQueryingEnumerable<T> : IEnumerable<T>, IAsyncEnume
             private readonly Func<CosmosQueryContext, JObject, T> _shaper;
             private readonly Type _contextType;
             private readonly IDiagnosticsLogger<DbLoggerCategory.Query> _logger;
+            private readonly bool _performIdentityResolution;
 
             public ReadItemQueryingEnumerable(
                 CosmosQueryContext cosmosQueryContext,
                 ReadItemExpression readItemExpression,
                 Func<CosmosQueryContext, JObject, T> shaper,
                 Type contextType,
-                IDiagnosticsLogger<DbLoggerCategory.Query> logger)
+                IDiagnosticsLogger<DbLoggerCategory.Query> logger,
+                bool performIdentityResolution)
             {
                 _cosmosQueryContext = cosmosQueryContext;
                 _readItemExpression = readItemExpression;
                 _shaper = shaper;
                 _contextType = contextType;
                 _logger = logger;
+                _performIdentityResolution = performIdentityResolution;
             }
 
             public IAsyncEnumerator<T> GetAsyncEnumerator(CancellationToken cancellationToken = default)
@@ -68,6 +72,7 @@ private sealed class Enumerator : IEnumerator<T>, IAsyncEnumerator<T>
                 private readonly Func<CosmosQueryContext, JObject, T> _shaper;
                 private readonly Type _contextType;
                 private readonly IDiagnosticsLogger<DbLoggerCategory.Query> _logger;
+                private readonly bool _performIdentityResolution;
                 private readonly CancellationToken _cancellationToken;
 
                 private JObject _item;
@@ -80,6 +85,7 @@ public Enumerator(ReadItemQueryingEnumerable<T> readItemEnumerable, Cancellation
                     _shaper = readItemEnumerable._shaper;
                     _contextType = readItemEnumerable._contextType;
                     _logger = readItemEnumerable._logger;
+                    _performIdentityResolution = readItemEnumerable._performIdentityResolution;
                     _cancellationToken = cancellationToken;
                 }
 
@@ -182,6 +188,8 @@ private bool ShapeResult()
                 {
                     var hasNext = !(_item is null);
 
+                    _cosmosQueryContext.InitializeStateManager(_performIdentityResolution);
+
                     Current
                         = hasNext
                             ? _shaper(_cosmosQueryContext, _item)
@@ -246,10 +254,10 @@ private bool TryGenerateIdFromKeys(IProperty idProperty, out object value)
                 {
                     var entityEntry = Activator.CreateInstance(_readItemExpression.EntityType.ClrType);
 
-#pragma warning disable EF1001 // Internal EF Core API usage.
+#pragma warning disable EF1001
                     var internalEntityEntry = new InternalEntityEntryFactory().Create(
-                        _cosmosQueryContext.StateManager, _readItemExpression.EntityType, entityEntry);
-#pragma warning restore EF1001 // Internal EF Core API usage.
+                        _cosmosQueryContext.Context.GetDependencies().StateManager, _readItemExpression.EntityType, entityEntry);
+#pragma warning restore EF1001
 
                     foreach (var keyProperty in _readItemExpression.EntityType.FindPrimaryKey().Properties)
                     {

diff --git a/src/EFCore.Cosmos/Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.cs b/src/EFCore.Cosmos/Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.cs
@@ -87,7 +87,8 @@ protected override Expression VisitShapedQuery(ShapedQueryExpression shapedQuery
                         Expression.Constant(shaperLambda.Compile()),
                         Expression.Constant(_contextType),
                         Expression.Constant(_partitionKeyFromExtension, typeof(string)),
-                        Expression.Constant(_logger));
+                        Expression.Constant(_logger),
+                        Expression.Constant(QueryCompilationContext.PerformIdentityResolution));
 
                 case ReadItemExpression readItemExpression:
 
@@ -108,7 +109,8 @@ protected override Expression VisitShapedQuery(ShapedQueryExpression shapedQuery
                         Expression.Constant(readItemExpression),
                         Expression.Constant(shaperReadItemLambda.Compile()),
                         Expression.Constant(_contextType),
-                        Expression.Constant(_logger));
+                        Expression.Constant(_logger),
+                        Expression.Constant(QueryCompilationContext.PerformIdentityResolution));
 
                 default:
                     throw new NotImplementedException();

diff --git a/src/EFCore.Cosmos/Query/Internal/SelectExpression.cs b/src/EFCore.Cosmos/Query/Internal/SelectExpression.cs
@@ -133,7 +133,7 @@ public SelectExpression(
         public virtual Expression GetMappedProjection([NotNull] ProjectionMember projectionMember)
             => _projectionMapping[projectionMember];
 
-        
+
         /// <summary>
         ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
         ///     the same compatibility standards as public APIs. It may be changed or removed without notice in

diff --git a/...Memory/Query/Internal/InMemoryShapedQueryCompilingExpressionVisitor.QueryingEnumerable.cs b/...Memory/Query/Internal/InMemoryShapedQueryCompilingExpressionVisitor.QueryingEnumerable.cs
@@ -29,19 +29,22 @@ private sealed class QueryingEnumerable<T> : IAsyncEnumerable<T>, IEnumerable<T>
             private readonly Func<QueryContext, ValueBuffer, T> _shaper;
             private readonly Type _contextType;
             private readonly IDiagnosticsLogger<DbLoggerCategory.Query> _logger;
+            private readonly bool _performIdentityResolution;
 
             public QueryingEnumerable(
                 QueryContext queryContext,
                 IEnumerable<ValueBuffer> innerEnumerable,
                 Func<QueryContext, ValueBuffer, T> shaper,
                 Type contextType,
-                IDiagnosticsLogger<DbLoggerCategory.Query> logger)
+                IDiagnosticsLogger<DbLoggerCategory.Query> logger,
+                bool performIdentityResolution)
             {
                 _queryContext = queryContext;
                 _innerEnumerable = innerEnumerable;
                 _shaper = shaper;
                 _contextType = contextType;
                 _logger = logger;
+                _performIdentityResolution = performIdentityResolution;
             }
 
             public IAsyncEnumerator<T> GetAsyncEnumerator(CancellationToken cancellationToken = default)
@@ -61,6 +64,7 @@ private sealed class Enumerator : IEnumerator<T>, IAsyncEnumerator<T>
                 private readonly Func<QueryContext, ValueBuffer, T> _shaper;
                 private readonly Type _contextType;
                 private readonly IDiagnosticsLogger<DbLoggerCategory.Query> _logger;
+                private readonly bool _performIdentityResolution;
                 private readonly CancellationToken _cancellationToken;
 
                 public Enumerator(QueryingEnumerable<T> queryingEnumerable, CancellationToken cancellationToken = default)
@@ -70,6 +74,7 @@ public Enumerator(QueryingEnumerable<T> queryingEnumerable, CancellationToken ca
                     _shaper = queryingEnumerable._shaper;
                     _contextType = queryingEnumerable._contextType;
                     _logger = queryingEnumerable._logger;
+                    _performIdentityResolution = queryingEnumerable._performIdentityResolution;
                     _cancellationToken = cancellationToken;
                 }
 
@@ -118,6 +123,7 @@ private bool MoveNextHelper()
                     if (_enumerator == null)
                     {
                         _enumerator = _innerEnumerable.GetEnumerator();
+                        _queryContext.InitializeStateManager(_performIdentityResolution);
                     }
 
                     var hasNext = _enumerator.MoveNext();

diff --git a/src/EFCore.InMemory/Query/Internal/InMemoryShapedQueryCompilingExpressionVisitor.cs b/src/EFCore.InMemory/Query/Internal/InMemoryShapedQueryCompilingExpressionVisitor.cs
@@ -92,7 +92,8 @@ protected override Expression VisitShapedQuery(ShapedQueryExpression shapedQuery
                 innerEnumerable,
                 Expression.Constant(shaperLambda.Compile()),
                 Expression.Constant(_contextType),
-                Expression.Constant(_logger));
+                Expression.Constant(_logger),
+                Expression.Constant(QueryCompilationContext.PerformIdentityResolution));
         }
 
         private static readonly MethodInfo _tableMethodInfo

diff --git a/src/EFCore.Relational/Query/Internal/QueryingEnumerable.cs b/src/EFCore.Relational/Query/Internal/QueryingEnumerable.cs
@@ -29,6 +29,7 @@ public class QueryingEnumerable<T> : IEnumerable<T>, IAsyncEnumerable<T>, IRelat
         private readonly Func<QueryContext, DbDataReader, ResultContext, int[], ResultCoordinator, T> _shaper;
         private readonly Type _contextType;
         private readonly IDiagnosticsLogger<DbLoggerCategory.Query> _logger;
+        private readonly bool _performIdentityResolution;
 
         /// <summary>
         ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
@@ -43,7 +44,8 @@ public QueryingEnumerable(
             [NotNull] IReadOnlyList<ReaderColumn> readerColumns,
             [NotNull] Func<QueryContext, DbDataReader, ResultContext, int[], ResultCoordinator, T> shaper,
             [NotNull] Type contextType,
-            [NotNull] IDiagnosticsLogger<DbLoggerCategory.Query> logger)
+            [NotNull] IDiagnosticsLogger<DbLoggerCategory.Query> logger,
+            bool performIdentityResolution)
         {
             _relationalQueryContext = relationalQueryContext;
             _relationalCommandCache = relationalCommandCache;
@@ -52,6 +54,7 @@ public QueryingEnumerable(
             _shaper = shaper;
             _contextType = contextType;
             _logger = logger;
+            _performIdentityResolution = performIdentityResolution;
         }
 
         /// <summary>
@@ -148,6 +151,7 @@ private sealed class Enumerator : IEnumerator<T>
             private readonly Func<QueryContext, DbDataReader, ResultContext, int[], ResultCoordinator, T> _shaper;
             private readonly Type _contextType;
             private readonly IDiagnosticsLogger<DbLoggerCategory.Query> _logger;
+            private readonly bool _performIdentityResolution;
 
             private RelationalDataReader _dataReader;
             private int[] _indexMap;
@@ -163,6 +167,7 @@ public Enumerator(QueryingEnumerable<T> queryingEnumerable)
                 _shaper = queryingEnumerable._shaper;
                 _contextType = queryingEnumerable._contextType;
                 _logger = queryingEnumerable._logger;
+                _performIdentityResolution = queryingEnumerable._performIdentityResolution;
             }
 
             public T Current { get; private set; }
@@ -246,6 +251,8 @@ private bool InitializeReader(DbContext _, bool result)
 
                 _resultCoordinator = new ResultCoordinator();
 
+                _relationalQueryContext.InitializeStateManager(_performIdentityResolution);
+
                 return result;
             }
 
@@ -267,6 +274,7 @@ private sealed class AsyncEnumerator : IAsyncEnumerator<T>
             private readonly Func<QueryContext, DbDataReader, ResultContext, int[], ResultCoordinator, T> _shaper;
             private readonly Type _contextType;
             private readonly IDiagnosticsLogger<DbLoggerCategory.Query> _logger;
+            private readonly bool _performIdentityResolution;
             private readonly CancellationToken _cancellationToken;
 
             private RelationalDataReader _dataReader;
@@ -285,6 +293,7 @@ public AsyncEnumerator(
                 _shaper = queryingEnumerable._shaper;
                 _contextType = queryingEnumerable._contextType;
                 _logger = queryingEnumerable._logger;
+                _performIdentityResolution = queryingEnumerable._performIdentityResolution;
                 _cancellationToken = cancellationToken;
             }
 
@@ -368,6 +377,8 @@ private async Task<bool> InitializeReaderAsync(DbContext _, bool result, Cancell
 
                 _resultCoordinator = new ResultCoordinator();
 
+                _relationalQueryContext.InitializeStateManager(_performIdentityResolution);
+
                 return result;
             }
 

diff --git a/src/EFCore.Relational/Query/RelationalShapedQueryCompilingExpressionVisitor.cs b/src/EFCore.Relational/Query/RelationalShapedQueryCompilingExpressionVisitor.cs
@@ -99,7 +99,8 @@ protected override Expression VisitShapedQuery(ShapedQueryExpression shapedQuery
                 Expression.Constant(projectionColumns, typeof(IReadOnlyList<ReaderColumn>)),
                 Expression.Constant(shaperLambda.Compile()),
                 Expression.Constant(_contextType),
-                Expression.Constant(_logger));
+                Expression.Constant(_logger),
+                Expression.Constant(QueryCompilationContext.PerformIdentityResolution));
         }
     }
 }
diff --git a/src/EFCore/Extensions/EntityFrameworkQueryableExtensions.cs b/src/EFCore/Extensions/EntityFrameworkQueryableExtensions.cs
@@ -2530,6 +2530,44 @@ public static IQueryable<TEntity> AsTracking<TEntity>(
                 ? source.AsTracking()
                 : source.AsNoTracking();
 
+        internal static readonly MethodInfo PerformIdentityResolutionMethodInfo
+            = typeof(EntityFrameworkQueryableExtensions)
+                .GetTypeInfo().GetDeclaredMethod(nameof(PerformIdentityResolution));
+
+        /// <summary>
+        ///     <para>
+        ///         Returns a new query where the change tracker will not track any of the entities that are return
+        ///         but query will perform identity resolution in results.
+        ///         If the entity instances are modified, this will not be detected by the change tracker and
+        ///         <see cref="DbContext.SaveChanges()" /> will not persist those changes to the database.
+        ///     </para>
+        ///     <para>
+        ///         Perfoming identity resolution in no tracking query can be useful if creating several instances of same object is
+        ///         expensive than re-using same object. It should be kept in mind that in order to perform identity resolution,
+        ///         all previously created objects will be kept in memory which can lead to high memory usage.
+        ///     </para>
+        /// </summary>
+        /// <typeparam name="TEntity"> The type of entity being queried. </typeparam>
+        /// <param name="source"> The source query. </param>
+        /// <returns>
+        ///     A new query where the result set will not be tracked by the context.
+        /// </returns>
+        public static IQueryable<TEntity> PerformIdentityResolution<TEntity>(
+            [NotNull] this IQueryable<TEntity> source)
+            where TEntity : class
+        {
+            Check.NotNull(source, nameof(source));
+
+            return
+                source.Provider is EntityQueryProvider
+                    ? source.Provider.CreateQuery<TEntity>(
+                        Expression.Call(
+                            instance: null,
+                            method: PerformIdentityResolutionMethodInfo.MakeGenericMethod(typeof(TEntity)),
+                            arguments: source.Expression))
+                    : source;
+        }
+
         #endregion
 
         #region Tagging