CSHARP-4095: Use count command for estimatedDocumentCount. (#789)

Author: JamesKovacs

Docs/reference/content/reference/driver/stable_api.md

@@ -67,3 +67,12 @@ var database = client.GetDatabase("db");
 var result = database.RunCommand<BsonDocument>(new BsonDocument("commandDeprecatedInV1", 1)); // Example fail:
 // MongoDB.Driver.MongoCommandException : Command commandDeprecatedInV1 failed: Provided deprecationErrors:true, but the command commandDeprecatedInV1 is deprecated in API Version 1.
 ```
+
+### EstimatedDocumentCount and Stable API
+
+`EstimatedDocumentCount` is implemented using the `count` server command. Due to an oversight in versions
+5.0.0-5.0.8 of MongoDB, the `count` command, which `EstimatedDocumentCount` uses in its implementation,
+was not included in v1 of the Stable API. If you are using the Stable API with `EstimatedDocumentCount`,
+you must upgrade to server version 5.0.9+ or set `strict: false` when configuring `ServerApi` to avoid
+encountering errors.
+

src/MongoDB.Driver.Core/Core/Misc/Feature.cs

@@ -1,4 +1,4 @@
-/* Copyright 2016-present MongoDB Inc.
+/* Copyright 2016-present MongoDB Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -59,7 +59,6 @@ public class Feature
         private static readonly Feature __currentOpCommand = new Feature("CurrentOpCommand", WireVersion.Server32);
         private static readonly Feature __documentValidation = new Feature("DocumentValidation", WireVersion.Server32);
         private static readonly Feature __directConnectionSetting = new Feature("DirectConnectionSetting", WireVersion.Server44);
-        private static readonly Feature __estimatedDocumentCountByCollStats = new Feature("EstimatedDocumentCountByCollStats", WireVersion.Server49);
         private static readonly Feature __eval = new Feature("Eval", WireVersion.Zero, WireVersion.Server42);
         private static readonly Feature __explainCommand = new Feature("ExplainCommand", WireVersion.Server30);
         private static readonly Feature __failPoints = new Feature("FailPoints", WireVersion.Zero);
@@ -318,11 +317,6 @@ public class Feature
         /// </summary>
         public static Feature DirectConnectionSetting => __directConnectionSetting;
 
-        /// <summary>
-        /// Gets the estimatedDocumentCountByCollStats feature.
-        /// </summary>
-        public static Feature EstimatedDocumentCountByCollStats => __estimatedDocumentCountByCollStats;
-
         /// <summary>
         /// Gets the eval feature.
         /// </summary>
@@ -692,7 +686,7 @@ internal void ThrowIfNotSupported(int wireVersion)
         {
             if (!IsSupported(wireVersion))
             {
-                string errorMessage; 
+                string errorMessage;
                 if (_notSupportedMessage != null)
                 {
                     errorMessage = _notSupportedMessage; ;

src/MongoDB.Driver.Core/Core/Operations/EstimatedDocumentCountOperation.cs

@@ -14,11 +14,9 @@
 */
 
 using System;
-using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
 using MongoDB.Bson;
-using MongoDB.Bson.Serialization.Serializers;
 using MongoDB.Driver.Core.Bindings;
 using MongoDB.Driver.Core.Misc;
 using MongoDB.Driver.Core.WireProtocol.Messages.Encoders;
@@ -104,29 +102,9 @@ public long Execute(IReadBinding binding, CancellationToken cancellationToken)
 
             using (var context = RetryableReadContext.Create(binding, _retryRequested, cancellationToken))
             {
-                if (Feature.EstimatedDocumentCountByCollStats.IsSupported(context.Channel.ConnectionDescription.MaxWireVersion))
-                {
-                    var operation = CreateAggregationOperation();
-                    IAsyncCursor<BsonDocument> cursor;
-                    try
-                    {
-                        cursor = operation.Execute(context, cancellationToken);
-                    }
-                    catch (MongoCommandException ex) when (ex.Code == (int)ServerErrorCode.NamespaceNotFound)
-                    {
-                        // In the event this aggregation is run against a non-existent namespace, a NamespaceNotFound(26) error will be returned during execution.
-                        return 0;
-                    }
-                    var results = cursor.ToList(cancellationToken);
-
-                    return ExtractCountFromAggregationResults(results);
-                }
-                else
-                {
-                    var operation = CreateCountOperation();
-
-                    return operation.Execute(context, cancellationToken);
-                }
+                var operation = CreateCountOperation();
+
+                return operation.Execute(context, cancellationToken);
             }
         }
 
@@ -137,58 +115,13 @@ public async Task<long> ExecuteAsync(IReadBinding binding, CancellationToken can
 
             using (var context = RetryableReadContext.Create(binding, _retryRequested, cancellationToken))
             {
-                if (Feature.EstimatedDocumentCountByCollStats.IsSupported(context.Channel.ConnectionDescription.MaxWireVersion))
-                {
-                    var operation = CreateAggregationOperation();
-                    IAsyncCursor<BsonDocument> cursor;
-                    try
-                    {
-                        cursor = await operation.ExecuteAsync(context, cancellationToken).ConfigureAwait(false);
-                    }
-                    catch (MongoCommandException ex) when (ex.Code == (int)ServerErrorCode.NamespaceNotFound)
-                    {
-                        // In the event this aggregation is run against a non-existent namespace, a NamespaceNotFound(26) error will be returned during execution.
-                        return 0;
-                    }
-                    var results = await cursor.ToListAsync(cancellationToken).ConfigureAwait(false);
-
-                    return ExtractCountFromAggregationResults(results);
-                }
-                else
-                {
-                    var operation = CreateCountOperation();
-
-                    return await operation.ExecuteAsync(context, cancellationToken).ConfigureAwait(false);
-                }
+                var operation = CreateCountOperation();
+
+                return await operation.ExecuteAsync(context, cancellationToken).ConfigureAwait(false);
             }
         }
 
         // private methods
-        private IExecutableInRetryableReadContext<IAsyncCursor<BsonDocument>> CreateAggregationOperation()
-        {
-            var pipeline = CreateAggregationPipeline();
-            var aggregateOperation = new AggregateOperation<BsonDocument>(_collectionNamespace, pipeline, BsonDocumentSerializer.Instance, _messageEncoderSettings)
-            {
-                MaxTime = _maxTime,
-                ReadConcern = _readConcern,
-                RetryRequested = _retryRequested
-            };
-            return aggregateOperation;
-
-            IEnumerable<BsonDocument> CreateAggregationPipeline() =>
-                new BsonDocument[]
-                {
-                    new BsonDocument("$collStats", new BsonDocument("count", new BsonDocument())),
-                    new BsonDocument(
-                        "$group",
-                        new BsonDocument
-                        {
-                            { "_id", 1 },
-                            { "n", new BsonDocument("$sum", "$count") }
-                        })
-                };
-        }
-
         private IExecutableInRetryableReadContext<long> CreateCountOperation()
         {
             var countOperation = new CountOperation(_collectionNamespace, _messageEncoderSettings)
@@ -200,13 +133,5 @@ private IExecutableInRetryableReadContext<long> CreateCountOperation()
             };
             return countOperation;
         }
-
-        private long ExtractCountFromAggregationResults(List<BsonDocument> results) =>
-            results.Count switch
-            {
-                0 => 0,
-                1 => results[0]["n"].ToInt64(),
-                _ => throw new MongoClientException($"Expected aggregate command for {nameof(EstimatedDocumentCountOperation)} to return 1 document, but got {results.Count}."),
-            };
     }
 }

src/MongoDB.Driver/IMongoCollection.cs

@@ -242,7 +242,7 @@ public interface IMongoCollection<TDocument>
         /// </summary>
         /// <remarks>
         /// Note: when migrating from Count to CountDocuments the following query operations must be replaced:
-        /// 
+        ///
         /// <code>
         /// +-------------+--------------------------------+
         /// | Operator    | Replacement                    |
@@ -269,7 +269,7 @@ public interface IMongoCollection<TDocument>
         /// </summary>
         /// <remarks>
         /// Note: when migrating from Count to CountDocuments the following query operations must be replaced:
-        /// 
+        ///
         /// <code>
         /// +-------------+--------------------------------+
         /// | Operator    | Replacement                    |
@@ -297,7 +297,7 @@ public interface IMongoCollection<TDocument>
         /// </summary>
         /// <remarks>
         /// Note: when migrating from CountAsync to CountDocumentsAsync the following query operations must be replaced:
-        /// 
+        ///
         /// <code>
         /// +-------------+--------------------------------+
         /// | Operator    | Replacement                    |
@@ -324,7 +324,7 @@ public interface IMongoCollection<TDocument>
         /// </summary>
         /// <remarks>
         /// Note: when migrating from CountAsync to CountDocumentsAsync the following query operations must be replaced:
-        /// 
+        ///
         /// <code>
         /// +-------------+--------------------------------+
         /// | Operator    | Replacement                    |
@@ -536,6 +536,12 @@ public interface IMongoCollection<TDocument>
         /// <returns>
         /// An estimate of the number of documents in the collection.
         /// </returns>
+        /// <remarks>
+        /// Due to an oversight in versions 5.0.0-5.0.8 of MongoDB, the count command, which estimatedDocumentCount uses
+        /// in its implementation, was not included in v1 of the Stable API. If you are using the Stable API with
+        /// estimatedDocumentCount, you must upgrade to server version 5.0.9+ or set strict: false when configuring
+        /// ServerApi to avoid encountering errors.
+        /// </remarks>
         long EstimatedDocumentCount(EstimatedDocumentCountOptions options = null, CancellationToken cancellationToken = default(CancellationToken));
 
         /// <summary>

tests/MongoDB.Driver.Core.Tests/Core/Operations/EstimatedDocumentCountOperationTests.cs

@@ -1,4 +1,4 @@
-/* Copyright 2021-present MongoDB Inc.
+/* Copyright 2021-present MongoDB Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -21,7 +21,6 @@
 using MongoDB.Driver.Core.Bindings;
 using MongoDB.Driver.Core.Clusters;
 using MongoDB.Driver.Core.Connections;
-using MongoDB.Driver.Core.Misc;
 using MongoDB.Driver.Core.TestHelpers;
 using MongoDB.Driver.Core.TestHelpers.XunitExtensions;
 using Xunit;
@@ -296,68 +295,29 @@ public void Execute_should_send_session_id_when_supported([Values(false, true)]
             EnsureTestData();
             var subject = new EstimatedDocumentCountOperation(_collectionNamespace, _messageEncoderSettings);
 
-            if (Feature.EstimatedDocumentCountByCollStats.IsSupported(CoreTestConfiguration.MaxWireVersion))
-            {
-                VerifySessionIdWasSentWhenSupported(subject, "aggregate", async);
-            }
-            else
-            {
-                VerifySessionIdWasSentWhenSupported(subject, "count", async);
-            }
+            VerifySessionIdWasSentWhenSupported(subject, "count", async);
         }
 
         // private methods
         private void AssertCommandDocument(BsonDocument actualResult, int? expectedMaxTimeMS = null, BsonDocument readConcern = null)
         {
-            if (Feature.EstimatedDocumentCountByCollStats.IsSupported(CoreTestConfiguration.MaxWireVersion))
+            var expectedResult = new BsonDocument
             {
-                var expectedResult = new BsonDocument
-                {
-                    { "aggregate", _collectionNamespace.CollectionName },
-                    {
-                        "pipeline",
-                        BsonArray.Create(
-                            new []
-                            {
-                                BsonDocument.Parse("{ $collStats : { count : { } } }"),
-                                BsonDocument.Parse("{ $group : { _id : 1, n : { $sum : '$count' } } } ")
-                            })
-                    },
-                    { "maxTimeMS", () => expectedMaxTimeMS.Value, expectedMaxTimeMS.HasValue },
-                    { "readConcern", () => readConcern, readConcern != null },
-                    { "cursor", new BsonDocument() }
-                };
-                actualResult.Should().Be(expectedResult);
-            }
-            else
+                { "count", _collectionNamespace.CollectionName },
+                { "maxTimeMS", () => expectedMaxTimeMS.Value, expectedMaxTimeMS.HasValue },
+                { "readConcern", () => readConcern, readConcern != null }
+            };
+            actualResult.Should().Be(expectedResult);
+            if (actualResult.TryGetValue("maxTimeMS", out var maxTimeMS))
             {
-                var expectedResult = new BsonDocument
-                {
-                    { "count", _collectionNamespace.CollectionName },
-                    { "maxTimeMS", () => expectedMaxTimeMS.Value, expectedMaxTimeMS.HasValue },
-                    { "readConcern", () => readConcern, readConcern != null }
-                };
-                actualResult.Should().Be(expectedResult);
-                if (actualResult.TryGetValue("maxTimeMS", out var maxTimeMS))
-                {
-                    maxTimeMS.BsonType.Should().Be(BsonType.Int32);
-                }
+                maxTimeMS.BsonType.Should().Be(BsonType.Int32);
             }
         }
 
         private BsonDocument CreateCommand(EstimatedDocumentCountOperation subject, ConnectionDescription connectionDescription, ICoreSession session)
         {
-            var currentServerVersion = CoreTestConfiguration.ServerVersion;
-            if (Feature.EstimatedDocumentCountByCollStats.IsSupported(CoreTestConfiguration.MaxWireVersion))
-            {
-                var aggregationOperation = (AggregateOperation<BsonDocument>)subject.CreateAggregationOperation();
-                return aggregationOperation.CreateCommand(connectionDescription, session);
-            }
-            else
-            {
-                var countOperation = (CountOperation)subject.CreateCountOperation();
-                return countOperation.CreateCommand(connectionDescription, session);
-            }
+            var countOperation = (CountOperation)subject.CreateCountOperation();
+            return countOperation.CreateCommand(connectionDescription, session);
         }
 
         private void EnsureTestData()
@@ -373,11 +333,6 @@ private void EnsureTestData()
 
     internal static class EstimatedDocumentCountOperationReflector
     {
-        public static IExecutableInRetryableReadContext<IAsyncCursor<BsonDocument>> CreateAggregationOperation(this EstimatedDocumentCountOperation operation)
-        {
-            return (IExecutableInRetryableReadContext<IAsyncCursor<BsonDocument>>)Reflector.Invoke(operation, nameof(CreateAggregationOperation));
-        }
-
         public static IExecutableInRetryableReadContext<long> CreateCountOperation(this EstimatedDocumentCountOperation operation)
         {
             return (IExecutableInRetryableReadContext<long>)Reflector.Invoke(operation, nameof(CreateCountOperation));

tests/MongoDB.Driver.Tests/Specifications/crud/tests/README.rst

@@ -21,12 +21,12 @@ Subdirectories for Test Formats
 
 This document describes a legacy format for CRUD tests: legacy-v1, which dates back
 to the first version of the CRUD specification. New CRUD tests should be written
-in the `unified test format <../../../../unified-test-format/unified-test-format.rst>`_
+in the `unified test format <../../unified-test-format/unified-test-format.rst>`_
 and placed under ``unified/``. Until such time that all original tests have been ported
 to the unified test format, tests in each format will be grouped in their own subdirectory:
 
 - ``v1/``: Legacy-v1 format tests
-- ``unified/``: Tests using the `unified test format <../../../../unified-test-format/unified-test-format.rst>`_
+- ``unified/``: Tests using the `unified test format <../../unified-test-format/unified-test-format.rst>`_
 
 Since some drivers may not have a unified test runner capable of executing tests
 in all two formats, segregating tests in this manner will make it easier for
@@ -52,11 +52,13 @@ single operation. Notable differences from the legacy-v2 format are as follows:
   fields.
 
 - Instead of a top-level ``runOn`` field, server requirements are denoted by
-  separate top-level ``minServerVersion`` and ``maxServerVersion`` fields. The
-  minimum server version is an inclusive lower bound for running the test. The
-  maximum server version is an exclusive upper bound for running the test. If a
-  field is not present, it should be assumed that there is no corresponding bound
-  on the required server version.
+  separate top-level ``minServerVersion``, ``maxServerVersion``, and
+  ``serverless`` fields. The minimum server version is an inclusive lower bound
+  for running the test. The maximum server version is an exclusive upper bound
+  for running the test. If a field is not present, it should be assumed that
+  there is no corresponding bound on the required server version. The
+  ``serverless`` requirement behaves the same as the ``serverless`` field of the
+  `unified test format's runOnRequirement <../../unified-test-format/unified-test-format.rst#runonrequirement>`_.
 
 The legacy-v1 format should not conflict with the newer, multi-operation format
 used by other specs (e.g. Transactions). It is possible to create a unified test
@@ -255,7 +257,7 @@ Test that ``writeErrors[].errInfo`` in a command response is propagated as
 ``WriteError.details`` (or equivalent) in the driver.
 
 Using a 5.0+ server, create a collection with
-`document validation <https://docs.mongodb.com/manual/core/schema-validation/>`_
+`document validation <https://www.mongodb.com/docs/manual/core/schema-validation/>`_
 like so:
 
 .. code:: javascript

tests/MongoDB.Driver.Tests/Specifications/crud/tests/unified/aggregate-merge.json

@@ -1,6 +1,6 @@
 {
   "description": "aggregate-merge",
-  "schemaVersion": "1.1",
+  "schemaVersion": "1.0",
   "runOnRequirements": [
     {
       "minServerVersion": "4.1.11"

tests/MongoDB.Driver.Tests/Specifications/crud/tests/unified/aggregate-merge.yml

@@ -2,7 +2,7 @@
 # Please review the generated file, then remove this notice.
 
 description: aggregate-merge
-schemaVersion: '1.1'
+schemaVersion: '1.0'
 runOnRequirements:
   -
     minServerVersion: 4.1.11

tests/MongoDB.Driver.Tests/Specifications/crud/tests/unified/bulkWrite-arrayFilters-clientError.json

@@ -1,6 +1,6 @@
 {
   "description": "bulkWrite-arrayFilters-clientError",
-  "schemaVersion": "1.1",
+  "schemaVersion": "1.0",
   "runOnRequirements": [
     {
       "maxServerVersion": "3.5.5"