Fix a bug causing query response to create a new stream for each content call

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosElementSerializer.cs

@@ -99,7 +99,7 @@ internal static CosmosArray ToCosmosElements(
         /// <param name="resourceType">The resource type</param>
         /// <param name="cosmosSerializationOptions">The custom serialization options. This allows custom serialization types like BSON, JSON, or other formats</param>
         /// <returns>Returns a memory stream of cosmos elements. By default the memory stream will contain JSON.</returns>
-        internal static Stream ToStream(
+        internal static MemoryStream ToStream(
             string containerRid,
             IEnumerable<CosmosElement> cosmosElements,
             ResourceType resourceType,

Microsoft.Azure.Cosmos/src/Query/v3Query/QueryResponse.cs

@@ -17,6 +17,8 @@ namespace Microsoft.Azure.Cosmos
     /// </summary>
     internal class QueryResponse : ResponseMessage
     {
+        private readonly Lazy<MemoryStream> memoryStream;
+
         /// <summary>
         /// Used for unit testing only
         /// </summary>
@@ -45,15 +47,22 @@ private QueryResponse(
             this.Count = count;
             this.ResponseLengthBytes = responseLengthBytes;
             this.queryMetrics = queryMetrics;
+            this.memoryStream = new Lazy<MemoryStream>(() => CosmosElementSerializer.ToStream(
+                        this.QueryHeaders.ContainerRid,
+                        this.CosmosElements,
+                        this.QueryHeaders.ResourceType,
+                        this.CosmosSerializationOptions));
         }
 
         public int Count { get; }
 
-        public override Stream Content => CosmosElementSerializer.ToStream(
-            this.QueryHeaders.ContainerRid,
-            this.CosmosElements,
-            this.QueryHeaders.ResourceType,
-            this.CosmosSerializationOptions);
+        public override Stream Content
+        {
+            get
+            {
+                return this.memoryStream.Value;
+            }
+        }
 
         internal virtual IEnumerable<CosmosElement> CosmosElements { get; }
 

Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/CosmosItemTests.cs

@@ -1107,6 +1107,7 @@ public async Task ItemQueryStreamSerializationSetting()
                 MemoryStream memoryStream = new MemoryStream();
                 response.Content.CopyTo(memoryStream);
                 byte[] content = memoryStream.ToArray();
+                response.Content.Position = 0;
 
                 // Examine the first buffer byte to determine the serialization format
                 byte firstByte = content[0];

Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/CosmosQueryUnitTests.cs

@@ -6,6 +6,7 @@ namespace Microsoft.Azure.Cosmos.Tests
 {
     using System;
     using System.Collections.Generic;
+    using System.IO;
     using System.Threading;
     using System.Threading.Tasks;
     using Microsoft.Azure.Cosmos.Query;
@@ -17,6 +18,42 @@ namespace Microsoft.Azure.Cosmos.Tests
     [TestClass]
     public class CosmosQueryUnitTests
     {
+        [TestMethod]
+        public void VerifyCosmosQueryResponseStream()
+        {
+            string contianerRid = "mockContainerRid";
+            (QueryResponseCore response, IList<ToDoItem> items) factoryResponse = QueryResponseMessageFactory.Create(
+                       itemIdPrefix: $"TestPage",
+                       continuationToken: "SomeContinuationToken",
+                       collectionRid: contianerRid,
+                       itemCount: 100);
+
+            QueryResponseCore responseCore = factoryResponse.response;
+
+            QueryResponse queryResponse = QueryResponse.CreateSuccess(
+                        result: responseCore.CosmosElements,
+                        count: responseCore.CosmosElements.Count,
+                        responseLengthBytes: responseCore.ResponseLengthBytes,
+                        queryMetrics: responseCore.QueryMetrics,
+                        responseHeaders: new CosmosQueryResponseMessageHeaders(
+                            responseCore.ContinuationToken,
+                            responseCore.DisallowContinuationTokenMessage,
+                            ResourceType.Document,
+                            contianerRid)
+                        {
+                            RequestCharge = responseCore.RequestCharge,
+                            ActivityId = responseCore.ActivityId
+                        });
+
+            using (Stream stream = queryResponse.Content)
+            {
+                using(Stream innerStream = queryResponse.Content)
+                {
+                    Assert.IsTrue(object.ReferenceEquals(stream, innerStream), "Content should return the same stream");
+                }
+            }
+        }
+
         [TestMethod]
         public async Task TestCosmosQueryExecutionComponentOnFailure()
         {

changelog.md

@@ -5,15 +5,18 @@ Preview features are treated as a separate branch and will not be included in th
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## Unreleased
+## Unreleased 
+
+### Fixed
+
+- [#901](https://github.com/Azure/azure-cosmos-dotnet-v3/pull/901) Fix a bug causing query response to create a new stream for each content call
 
 ## <a name="3.3.2"/> [3.3.2](https://www.nuget.org/packages/Microsoft.Azure.Cosmos/3.3.2) - 2019-10-16
 
 ### Fixed
 
 - [#905](https://github.com/Azure/azure-cosmos-dotnet-v3/pull/909) Fixed linq camel case bug
 
-
 ## <a name="3.3.1"/> [3.3.1](https://www.nuget.org/packages/Microsoft.Azure.Cosmos/3.3.1) - 2019-10-11
 
 ### Fixed