Fix for issue: CosmosDB to CosmosDB doesn't migrate "Id" field #100

Extensions/Cosmos/Cosmos.DataTransfer.CosmosExtension.UnitTests/CosmosDataSinkExtensionTests.cs

@@ -1,4 +1,5 @@
 using Cosmos.DataTransfer.Interfaces;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
 
 namespace Cosmos.DataTransfer.CosmosExtension.UnitTests
 {
@@ -54,5 +55,82 @@ public void BuildDynamicObjectTree_WithNestedArrays_WorksCorrectly()
 
             Assert.AreEqual("sub2-1", secondSubArray[0].id);
         }
+
+        [TestMethod]
+        public void BuildDynamicObjectTree_WithAnyCaseIds_UsesSourceIdValue()
+        {
+            var numeric = Random.Shared.Next();
+            var lower = Guid.NewGuid().ToString();
+            var upper = Guid.NewGuid().ToString();
+            var mixed = Guid.NewGuid().ToString();
+            var reversed = Guid.NewGuid().ToString();
+            var item = new CosmosDictionaryDataItem(new Dictionary<string, object?>()
+            {
+                { "id", numeric },
+            });
+
+            dynamic obj = item.BuildDynamicObjectTree(requireStringId: true, preserveMixedCaseIds: false)!;
+            Assert.AreEqual(numeric.ToString(), obj.id);
+
+            item = new CosmosDictionaryDataItem(new Dictionary<string, object?>()
+            {
+                { "id", lower },
+            });
+
+            obj = item.BuildDynamicObjectTree(requireStringId: true, preserveMixedCaseIds: false)!;
+            Assert.AreEqual(lower, obj.id);
+
+            item = new CosmosDictionaryDataItem(new Dictionary<string, object?>()
+            {
+                { "ID", upper },
+            });
+            obj = item.BuildDynamicObjectTree(requireStringId: true, preserveMixedCaseIds: false)!;
+            Assert.AreEqual(upper, obj.id);
+
+            item = new CosmosDictionaryDataItem(new Dictionary<string, object?>()
+            {
+                { "Id", mixed },
+            });
+            obj = item.BuildDynamicObjectTree(requireStringId: true, preserveMixedCaseIds: false)!;
+            Assert.AreEqual(mixed, obj.id);
+
+            item = new CosmosDictionaryDataItem(new Dictionary<string, object?>()
+            {
+                { "iD", reversed },
+            });
+            obj = item.BuildDynamicObjectTree(requireStringId: true, preserveMixedCaseIds: false)!;
+            Assert.AreEqual(reversed, obj.id);
+        }
+
+        [TestMethod]
+        public void BuildDynamicObjectTree_WithPreservedMixedCaseIds_PassesThroughSourceValues()
+        {
+            var id = Random.Shared.Next();
+            var upper = Guid.NewGuid().ToString();
+            var mixed = Guid.NewGuid().ToString();
+            var item = new CosmosDictionaryDataItem(new Dictionary<string, object?>()
+            {
+                { "id", id },
+                { "ID", upper },
+                { "Id", mixed }
+            });
+
+            dynamic obj = item.BuildDynamicObjectTree(requireStringId: true, preserveMixedCaseIds: true)!;
+            Assert.AreEqual(id.ToString(), obj.id);
+            Assert.AreEqual(upper, obj.ID);
+            Assert.AreEqual(mixed, obj.Id);
+
+            item = new CosmosDictionaryDataItem(new Dictionary<string, object?>()
+            {
+                { "ID", upper },
+                { "Id", mixed }
+            });
+            obj = item.BuildDynamicObjectTree(requireStringId: true, preserveMixedCaseIds: true)!;
+            Assert.AreEqual(upper, obj.ID);
+            Assert.AreEqual(mixed, obj.Id);
+            string? cosmosId = obj.id;
+            Assert.IsNotNull(cosmosId);
+            Assert.IsFalse(string.IsNullOrWhiteSpace(cosmosId));
+        }
     }
 }

Extensions/Cosmos/Cosmos.DataTransfer.CosmosExtension/CosmosDataSinkExtension.cs

@@ -93,7 +93,10 @@ void ReportCount(int i)
                 }
             }
 
-            var convertedObjects = dataItems.Select(di => di.BuildDynamicObjectTree(requireStringId: true, ignoreNullValues: settings.IgnoreNullValues)).Where(o => o != null).OfType<ExpandoObject>();
+            var convertedObjects = dataItems
+                .Select(di => di.BuildDynamicObjectTree(requireStringId: true, ignoreNullValues: settings.IgnoreNullValues, preserveMixedCaseIds: settings.PreserveMixedCaseIds))
+                .Where(o => o != null)
+                .OfType<ExpandoObject>();
             var batches = convertedObjects.Buffer(settings.BatchSize);
             var retry = GetRetryPolicy(settings.MaxRetryCount, settings.InitialRetryDurationMs);
             await foreach (var batch in batches.WithCancellation(cancellationToken))

Extensions/Cosmos/Cosmos.DataTransfer.CosmosExtension/CosmosSinkSettings.cs

@@ -14,6 +14,7 @@ public class CosmosSinkSettings : CosmosSettingsBase, IDataExtensionSettings
         public bool UseAutoscaleForCreatedContainer { get; set; } = true;
         public bool IsServerlessAccount { get; set; } = false;
         public bool UseSharedThroughput { get; set; } = false;
+        public bool PreserveMixedCaseIds { get; set; } = false;
         public DataWriteMode WriteMode { get; set; } = DataWriteMode.Insert;
         public bool IgnoreNullValues { get; set; } = false;
         public List<string>? PartitionKeyPaths { get; set; }

Extensions/Cosmos/README.md

@@ -44,7 +44,7 @@ Or with RBAC:
 }
 ```
 
-Sink requires an additional `PartitionKeyPath` parameter which is used when creating the container if it does not exist. To use hierarchical partition keys, instead use the `PartitionKeyPaths` setting to supply an array of up to 3 paths. It also supports an optional `RecreateContainer` parameter (`false` by default) to delete and then recreate the container to ensure only newly imported data is present. The optional `BatchSize` parameter (100 by default) sets the number of items to accumulate before inserting. `ConnectionMode` can be set to either `Gateway` (default) or `Direct` to control how the client connects to the CosmosDB service. For situations where a container is created as part of the transfer operation `CreatedContainerMaxThroughput` (in RUs) and `UseAutoscaleForCreatedContainer` provide the initial throughput settings which will be in effect when executing the transfer. To instead use shared throughput that has been provisioned at the database level, set the `UseSharedThroughput` parameter to `true`. The optional `WriteMode` parameter specifies the type of data write to use: `InsertStream`, `Insert`, `UpsertStream`, or `Upsert`. The `IsServerlessAccount` parameter specifies whether the target account uses Serverless instead of Provisioned throughput, which affects the way containers are created. Additional parameters allow changing the behavior of the Cosmos client appropriate to your environment.
+Sink requires an additional `PartitionKeyPath` parameter which is used when creating the container if it does not exist. To use hierarchical partition keys, instead use the `PartitionKeyPaths` setting to supply an array of up to 3 paths. It also supports an optional `RecreateContainer` parameter (`false` by default) to delete and then recreate the container to ensure only newly imported data is present. The optional `BatchSize` parameter (100 by default) sets the number of items to accumulate before inserting. `ConnectionMode` can be set to either `Gateway` (default) or `Direct` to control how the client connects to the CosmosDB service. For situations where a container is created as part of the transfer operation `CreatedContainerMaxThroughput` (in RUs) and `UseAutoscaleForCreatedContainer` provide the initial throughput settings which will be in effect when executing the transfer. To instead use shared throughput that has been provisioned at the database level, set the `UseSharedThroughput` parameter to `true`. The optional `WriteMode` parameter specifies the type of data write to use: `InsertStream`, `Insert`, `UpsertStream`, or `Upsert`. The `IsServerlessAccount` parameter specifies whether the target account uses Serverless instead of Provisioned throughput, which affects the way containers are created. Additional parameters allow changing the behavior of the Cosmos client appropriate to your environment. The `PreserveMixedCaseIds` parameter (`false` by default) ignores differently cased `id` fields and writes them through without modification, while generating a separate lowercased `id` field as required by Cosmos.
 
 ### Sink
 
@@ -62,6 +62,7 @@ Sink requires an additional `PartitionKeyPath` parameter which is used when crea
     "CreatedContainerMaxThroughput": 1000,
     "UseAutoscaleForCreatedContainer": true,
     "WriteMode": "InsertStream",
+    "PreserveMixedCaseIds": false,
     "IsServerlessAccount": false,
     "UseSharedThroughput": false
 }

Interfaces/Cosmos.DataTransfer.Interfaces/DataItemExtensions.cs

@@ -9,9 +9,10 @@ public static class DataItemExtensions
     /// </summary>
     /// <param name="source"></param>
     /// <param name="requireStringId">If true, adds a new GUID "id" field to any top level items where one is not already present.</param>
+    /// <param name="preserveMixedCaseIds">If true, disregards differently cased "id" fields for purposes of required "id" and passes them through.</param>
     /// <returns>A dynamic object containing the entire data structure.</returns>
     /// <remarks>The returned ExpandoObject can be used directly as an IDictionary.</remarks>
-    public static ExpandoObject? BuildDynamicObjectTree(this IDataItem? source, bool requireStringId = false, bool ignoreNullValues = false)
+    public static ExpandoObject? BuildDynamicObjectTree(this IDataItem? source, bool requireStringId = false, bool ignoreNullValues = false, bool preserveMixedCaseIds = false)
     {
         if (source == null) 
         {
@@ -20,20 +21,25 @@ public static class DataItemExtensions
 
         var fields = source.GetFieldNames().ToList();
         var item = new ExpandoObject();
-        
+
         /*
          * If the item contains a lowercase id field, we can take it as is.
-         * If we have an uppercase Id or ID field, but no lowercase id, we will rename it to id.
+         * If we have an uppercase Id or ID field, but no lowercase id, we will rename it to id, unless `preserveMixedCaseIds` is set to true.
+         * If `preserveMixedCaseIds` is set to true, any differently cased "id" fields will be passed through as normal properties with no casing change and a separate "id" will be generated.
          * Then it can be used i.e. as CosmosDB primary key, when `requireStringId` is set to true.         
          */
         var containsLowercaseIdField = fields.Contains("id", StringComparer.CurrentCulture);
         var containsAnyIdField = fields.Contains("id", StringComparer.CurrentCultureIgnoreCase);
-        
-        if (requireStringId && !containsAnyIdField)
+
+        if (requireStringId)
         {
-            item.TryAdd("id", Guid.NewGuid().ToString());
+            bool mismatchedIdCasing = preserveMixedCaseIds && !containsLowercaseIdField;
+            if (!containsAnyIdField || mismatchedIdCasing)
+            {
+                item.TryAdd("id", Guid.NewGuid().ToString());
+            }
         }
-        
+
         foreach (string field in fields)
         {
             object? value = source.GetValue(field);
@@ -43,10 +49,24 @@ public static class DataItemExtensions
             }
 
             var fieldName = field;
-            if (string.Equals(field, "id", StringComparison.CurrentCultureIgnoreCase) && requireStringId && !containsLowercaseIdField)
+            if (requireStringId && string.Equals(field, "id", StringComparison.CurrentCultureIgnoreCase))
             {
-                value = value?.ToString();
-                fieldName = "id";
+                if (preserveMixedCaseIds)
+                {
+                    if (string.Equals(field, "id", StringComparison.CurrentCulture))
+                    {
+                        value = value?.ToString();
+                    }
+                }
+                else if (!containsLowercaseIdField)
+                {
+                    value = value?.ToString();
+                    fieldName = "id";
+                }
+                else
+                {
+                    value = value?.ToString();
+                }
             }
             else if (value is IDataItem child)
             {