Fix LINQ Take() silently modifying cached QueryRequestOptions objects

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

@@ -142,13 +142,56 @@ public override async Task<TryCatch<QueryPage>> ExecuteItemQueryAsync(
             ITrace trace,
             CancellationToken cancellationToken)
         {
-            requestOptions.MaxItemCount = pageSize;
+            // Create a copy of the requestOptions to avoid modifying the original object
+            // that users might be caching. This fixes issue #5225.
+            QueryRequestOptions requestOptionsCopy = new QueryRequestOptions
+            {
+                ResponseContinuationTokenLimitInKb = requestOptions.ResponseContinuationTokenLimitInKb,
+                EnableScanInQuery = requestOptions.EnableScanInQuery,
+                EnableLowPrecisionOrderBy = requestOptions.EnableLowPrecisionOrderBy,
+                EnableOptimisticDirectExecution = requestOptions.EnableOptimisticDirectExecution,
+                MaxBufferedItemCount = requestOptions.MaxBufferedItemCount,
+                MaxItemCount = requestOptions.MaxItemCount,
+                MaxConcurrency = requestOptions.MaxConcurrency,
+                PartitionKey = requestOptions.PartitionKey,
+                PopulateIndexMetrics = requestOptions.PopulateIndexMetrics,
+                PopulateQueryAdvice = requestOptions.PopulateQueryAdvice,
+                ConsistencyLevel = requestOptions.ConsistencyLevel,
+                SessionToken = requestOptions.SessionToken,
+                DedicatedGatewayRequestOptions = requestOptions.DedicatedGatewayRequestOptions,
+                QueryTextMode = requestOptions.QueryTextMode,
+                CosmosElementContinuationToken = requestOptions.CosmosElementContinuationToken,
+                StartId = requestOptions.StartId,
+                EndId = requestOptions.EndId,
+                EnumerationDirection = requestOptions.EnumerationDirection,
+                CosmosSerializationFormatOptions = requestOptions.CosmosSerializationFormatOptions,
+                SupportedSerializationFormats = requestOptions.SupportedSerializationFormats,
+                ReturnResultsInDeterministicOrder = requestOptions.ReturnResultsInDeterministicOrder,
+                TestSettings = requestOptions.TestSettings,
+                FeedRange = requestOptions.FeedRange,
+                IsHybridSearchQueryPlanOptimizationDisabled = requestOptions.IsHybridSearchQueryPlanOptimizationDisabled,
+                EnableDistributedQueryGatewayMode = requestOptions.EnableDistributedQueryGatewayMode,
+                // Base RequestOptions properties
+                IfMatchEtag = requestOptions.IfMatchEtag,
+                IfNoneMatchEtag = requestOptions.IfNoneMatchEtag,
+                Properties = requestOptions.Properties,
+                AddRequestHeaders = requestOptions.AddRequestHeaders,
+                PriorityLevel = requestOptions.PriorityLevel,
+                CosmosThresholdOptions = requestOptions.CosmosThresholdOptions,
+                ExcludeRegions = requestOptions.ExcludeRegions,
+                AvailabilityStrategy = requestOptions.AvailabilityStrategy,
+                IsEffectivePartitionKeyRouting = requestOptions.IsEffectivePartitionKeyRouting,
+                BaseConsistencyLevel = requestOptions.BaseConsistencyLevel
+            };
+
+            // Now modify the copy instead of the original
+            requestOptionsCopy.MaxItemCount = pageSize;
 
             ResponseMessage message = await this.clientContext.ProcessResourceOperationStreamAsync(
                 resourceUri: resourceUri,
                 resourceType: resourceType,
                 operationType: operationType,
-                requestOptions: requestOptions,
+                requestOptions: requestOptionsCopy,
                 feedRange: feedRange,
                 cosmosContainerCore: this.cosmosContainerCore,
                 streamPayload: this.clientContext.SerializerCore.ToStreamSqlQuerySpec(sqlQuerySpec, resourceType),

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

@@ -6,6 +6,7 @@ namespace Microsoft.Azure.Cosmos
 {
     using System;
     using System.Collections.Generic;
+    using System.IO;
     using System.Text;
     using Microsoft.VisualStudio.TestTools.UnitTesting;
 
@@ -22,5 +23,78 @@ public void StatelessTest()
 
             Assert.IsNull(testMessage.Headers.ContinuationToken);
         }
+
+        [TestMethod]
+        public void MaxItemCountNotModifiedInOriginalQueryRequestOptions_SimpleCopyTest()
+        {
+            // This test verifies that when QueryRequestOptions properties are copied, 
+            // the original object is not modified. This reproduces the issue described in GitHub issue #5225.
+
+            QueryRequestOptions originalOptions = new QueryRequestOptions 
+            { 
+                MaxItemCount = -1,
+                MaxConcurrency = 10,
+                EnableScanInQuery = true,
+                SessionToken = "test-session-token"
+            };
+
+            int originalMaxItemCount = originalOptions.MaxItemCount.Value;
+            int? originalMaxConcurrency = originalOptions.MaxConcurrency;
+            bool? originalEnableScanInQuery = originalOptions.EnableScanInQuery;
+            string originalSessionToken = originalOptions.SessionToken;
+
+            // Simulate the copy logic that would happen in CosmosQueryClientCore.ExecuteItemQueryAsync
+            QueryRequestOptions requestOptionsCopy = new QueryRequestOptions
+            {
+                ResponseContinuationTokenLimitInKb = originalOptions.ResponseContinuationTokenLimitInKb,
+                EnableScanInQuery = originalOptions.EnableScanInQuery,
+                EnableLowPrecisionOrderBy = originalOptions.EnableLowPrecisionOrderBy,
+                EnableOptimisticDirectExecution = originalOptions.EnableOptimisticDirectExecution,
+                MaxBufferedItemCount = originalOptions.MaxBufferedItemCount,
+                MaxItemCount = originalOptions.MaxItemCount,
+                MaxConcurrency = originalOptions.MaxConcurrency,
+                PartitionKey = originalOptions.PartitionKey,
+                PopulateIndexMetrics = originalOptions.PopulateIndexMetrics,
+                PopulateQueryAdvice = originalOptions.PopulateQueryAdvice,
+                ConsistencyLevel = originalOptions.ConsistencyLevel,
+                SessionToken = originalOptions.SessionToken,
+                DedicatedGatewayRequestOptions = originalOptions.DedicatedGatewayRequestOptions,
+                QueryTextMode = originalOptions.QueryTextMode,
+                // Base RequestOptions properties
+                IfMatchEtag = originalOptions.IfMatchEtag,
+                IfNoneMatchEtag = originalOptions.IfNoneMatchEtag,
+                Properties = originalOptions.Properties,
+                AddRequestHeaders = originalOptions.AddRequestHeaders,
+                PriorityLevel = originalOptions.PriorityLevel,
+                CosmosThresholdOptions = originalOptions.CosmosThresholdOptions,
+                ExcludeRegions = originalOptions.ExcludeRegions
+            };
+
+            // Simulate the modification that would happen in ExecuteItemQueryAsync 
+            int pageSize = 5;
+            requestOptionsCopy.MaxItemCount = pageSize;
+
+            // Assert: The original QueryRequestOptions should NOT be modified
+            Assert.AreEqual(originalMaxItemCount, originalOptions.MaxItemCount.Value, 
+                "Original QueryRequestOptions.MaxItemCount should not be modified");
+            Assert.AreEqual(originalMaxConcurrency, originalOptions.MaxConcurrency, 
+                "Original QueryRequestOptions.MaxConcurrency should not be modified");
+            Assert.AreEqual(originalEnableScanInQuery, originalOptions.EnableScanInQuery, 
+                "Original QueryRequestOptions.EnableScanInQuery should not be modified");
+            Assert.AreEqual(originalSessionToken, originalOptions.SessionToken, 
+                "Original QueryRequestOptions.SessionToken should not be modified");
+
+            // Assert: The copy should have the new MaxItemCount
+            Assert.AreEqual(pageSize, requestOptionsCopy.MaxItemCount.Value, 
+                "Copied QueryRequestOptions.MaxItemCount should be updated to pageSize");
+
+            // Assert: Other properties should be preserved in the copy
+            Assert.AreEqual(originalMaxConcurrency, requestOptionsCopy.MaxConcurrency, 
+                "Copied QueryRequestOptions.MaxConcurrency should match original");
+            Assert.AreEqual(originalEnableScanInQuery, requestOptionsCopy.EnableScanInQuery, 
+                "Copied QueryRequestOptions.EnableScanInQuery should match original");
+            Assert.AreEqual(originalSessionToken, requestOptionsCopy.SessionToken, 
+                "Copied QueryRequestOptions.SessionToken should match original");
+        }
     }
 }