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CSHARP-2293: Implement new count API.
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‎src/MongoDB.Driver.Core/Core/Operations/CountDocumentsOperation.cs

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/* Copyright 2018-present MongoDB Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Collections.Generic;
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using System.Threading;
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using System.Threading.Tasks;
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using MongoDB.Bson;
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using MongoDB.Bson.Serialization.Serializers;
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using MongoDB.Driver.Core.Bindings;
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using MongoDB.Driver.Core.Misc;
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using MongoDB.Driver.Core.WireProtocol.Messages.Encoders;
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namespace MongoDB.Driver.Core.Operations
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{
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/// <summary>
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/// Represents a count documents operation.
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/// </summary>
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public class CountDocumentsOperation : IReadOperation<long>
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{
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// private fields
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private Collation _collation;
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private readonly CollectionNamespace _collectionNamespace;
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private BsonDocument _filter;
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private BsonValue _hint;
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private long? _limit;
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private TimeSpan? _maxTime;
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private readonly MessageEncoderSettings _messageEncoderSettings;
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private ReadConcern _readConcern = ReadConcern.Default;
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private long? _skip;
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// constructors
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/// <summary>
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/// Initializes a new instance of the <see cref="CountOperation"/> class.
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/// </summary>
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/// <param name="collectionNamespace">The collection namespace.</param>
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/// <param name="messageEncoderSettings">The message encoder settings.</param>
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public CountDocumentsOperation(CollectionNamespace collectionNamespace, MessageEncoderSettings messageEncoderSettings)
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{
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_collectionNamespace = Ensure.IsNotNull(collectionNamespace, nameof(collectionNamespace));
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_messageEncoderSettings = Ensure.IsNotNull(messageEncoderSettings, nameof(messageEncoderSettings));
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}
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// public properties
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/// <summary>
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/// Gets or sets the collation.
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/// </summary>
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/// <value>
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/// The collation.
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/// </value>
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public Collation Collation
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{
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get { return _collation; }
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set { _collation = value; }
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}
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/// <summary>
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/// Gets the collection namespace.
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/// </summary>
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/// <value>
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/// The collection namespace.
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/// </value>
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public CollectionNamespace CollectionNamespace
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{
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get { return _collectionNamespace; }
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}
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/// <summary>
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/// Gets or sets the filter.
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/// </summary>
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/// <value>
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/// The filter.
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/// </value>
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public BsonDocument Filter
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{
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get { return _filter; }
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set { _filter = value; }
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}
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/// <summary>
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/// Gets or sets the index hint.
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/// </summary>
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/// <value>
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/// The index hint.
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/// </value>
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public BsonValue Hint
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{
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get { return _hint; }
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set { _hint = value; }
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}
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/// <summary>
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/// Gets or sets a limit on the number of matching documents to count.
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/// </summary>
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/// <value>
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/// A limit on the number of matching documents to count.
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/// </value>
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public long? Limit
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{
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get { return _limit; }
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set { _limit = value; }
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}
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/// <summary>
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/// Gets or sets the maximum time the server should spend on this operation.
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/// </summary>
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/// <value>
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/// The maximum time the server should spend on this operation.
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/// </value>
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public TimeSpan? MaxTime
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{
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get { return _maxTime; }
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set { _maxTime = Ensure.IsNullOrInfiniteOrGreaterThanOrEqualToZero(value, nameof(value)); }
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}
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/// <summary>
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/// Gets the message encoder settings.
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/// </summary>
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/// <value>
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/// The message encoder settings.
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/// </value>
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public MessageEncoderSettings MessageEncoderSettings
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{
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get { return _messageEncoderSettings; }
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}
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/// <summary>
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/// Gets or sets the read concern.
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/// </summary>
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/// <value>
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/// The read concern.
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/// </value>
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public ReadConcern ReadConcern
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{
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get { return _readConcern; }
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set { _readConcern = Ensure.IsNotNull(value, nameof(value)); }
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}
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/// <summary>
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/// Gets or sets the number of documents to skip before counting the remaining matching documents.
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/// </summary>
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/// <value>
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/// The number of documents to skip before counting the remaining matching documents.
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/// </value>
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public long? Skip
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{
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get { return _skip; }
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set { _skip = value; }
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}
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// public methods
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/// <inheritdoc/>
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public long Execute(IReadBinding binding, CancellationToken cancellationToken)
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{
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Ensure.IsNotNull(binding, nameof(binding));
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using (var channelSource = binding.GetReadChannelSource(cancellationToken))
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using (var channel = channelSource.GetChannel(cancellationToken))
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using (var channelBinding = new ChannelReadBinding(channelSource.Server, channel, binding.ReadPreference, binding.Session.Fork()))
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{
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var operation = CreateOperation();
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var cursor = operation.Execute(channelBinding, cancellationToken);
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var result = cursor.ToList(cancellationToken);
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return ExtractCountFromResult(result);
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}
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}
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/// <inheritdoc/>
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public async Task<long> ExecuteAsync(IReadBinding binding, CancellationToken cancellationToken)
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{
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Ensure.IsNotNull(binding, nameof(binding));
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using (var channelSource = await binding.GetReadChannelSourceAsync(cancellationToken).ConfigureAwait(false))
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using (var channel = await channelSource.GetChannelAsync(cancellationToken).ConfigureAwait(false))
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using (var channelBinding = new ChannelReadBinding(channelSource.Server, channel, binding.ReadPreference, binding.Session.Fork()))
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{
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var operation = CreateOperation();
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var cursor = await operation.ExecuteAsync(channelBinding, cancellationToken).ConfigureAwait(false);
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var result = await cursor.ToListAsync(cancellationToken).ConfigureAwait(false);
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return ExtractCountFromResult(result);
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}
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}
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// private methods
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private AggregateOperation<BsonDocument> CreateOperation()
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{
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var pipeline = CreatePipeline();
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var operation = new AggregateOperation<BsonDocument>(_collectionNamespace, pipeline, BsonDocumentSerializer.Instance, _messageEncoderSettings)
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{
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Collation = _collation,
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Hint = _hint,
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MaxTime = _maxTime,
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ReadConcern = _readConcern
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};
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return operation;
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}
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private List<BsonDocument> CreatePipeline()
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{
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var pipeline = new List<BsonDocument>();
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pipeline.Add(new BsonDocument("$match", _filter ?? new BsonDocument()));
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if (_skip.HasValue)
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{
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pipeline.Add(new BsonDocument("$skip", _skip.Value));
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}
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if (_limit.HasValue)
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{
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pipeline.Add(new BsonDocument("$limit", _limit.Value));
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}
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pipeline.Add(new BsonDocument("$group", new BsonDocument { { "_id", BsonNull.Value }, { "n", new BsonDocument("$sum", 1) } }));
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return pipeline;
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}
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private long ExtractCountFromResult(List<BsonDocument> result)
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{
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switch (result.Count)
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{
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case 0:
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return 0;
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case 1:
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return result[0]["n"].ToInt64();
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default:
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throw new MongoClientException($"Expected aggregate command for CountDocuments to return 1 document, but got {result.Count}.");
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}
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}
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}
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}

‎src/MongoDB.Driver.Core/MongoDB.Driver.Core.csproj

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<Compile Include="Core\Operations\ChangeStreamCursor.cs" />
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<Compile Include="Core\Operations\ChangeStreamOperation.cs" />
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<Compile Include="Core\Clusters\ClusterClock.cs" />
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<Compile Include="Core\Operations\CountDocumentsOperation.cs" />
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<Compile Include="Core\Operations\CreateViewOperation.cs" />
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<Compile Include="Core\Clusters\IClusterClock.cs" />
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<Compile Include="Core\Operations\DelayedEvaluationWriteConcernSerializer.cs" />

‎src/MongoDB.Driver/EstimatedDocumentCountOptions.cs

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/* Copyright 2018-present MongoDB Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using MongoDB.Driver.Core.Misc;
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namespace MongoDB.Driver
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{
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/// <summary>
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/// Options for estimated document count.
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/// </summary>
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public sealed class EstimatedDocumentCountOptions
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{
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// private fields
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private TimeSpan? _maxTime;
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// public properties
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/// <summary>
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/// Gets or sets the maximum time.
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/// </summary>
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public TimeSpan? MaxTime
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{
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get { return _maxTime; }
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set { _maxTime = Ensure.IsNullOrInfiniteOrGreaterThanOrEqualToZero(value, nameof(value)); }
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}
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}
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}

‎src/MongoDB.Driver/FilteredMongoCollectionBase.cs

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* limitations under the License.
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*/
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Threading;
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return _wrappedCollection.BulkWriteAsync(session, CombineModelFilters(requests), options, cancellationToken);
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}
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[Obsolete("Use CountDocuments or EstimatedDocumentCount instead.")]
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public override long Count(FilterDefinition<TDocument> filter, CountOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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return _wrappedCollection.Count(CombineFilters(filter), options, cancellationToken);
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}
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[Obsolete("Use CountDocuments or EstimatedDocumentCount instead.")]
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public override long Count(IClientSessionHandle session, FilterDefinition<TDocument> filter, CountOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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return _wrappedCollection.Count(session, CombineFilters(filter), options, cancellationToken);
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}
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[Obsolete("Use CountDocumentsAsync or EstimatedDocumentCountAsync instead.")]
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public override Task<long> CountAsync(FilterDefinition<TDocument> filter, CountOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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return _wrappedCollection.CountAsync(CombineFilters(filter), options, cancellationToken);
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}
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[Obsolete("Use CountDocumentsAsync or EstimatedDocumentCountAsync instead.")]
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public override Task<long> CountAsync(IClientSessionHandle session, FilterDefinition<TDocument> filter, CountOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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return _wrappedCollection.CountAsync(session, CombineFilters(filter), options, cancellationToken);
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}
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public override long CountDocuments(FilterDefinition<TDocument> filter, CountOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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return _wrappedCollection.CountDocuments(CombineFilters(filter), options, cancellationToken);
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}
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public override long CountDocuments(IClientSessionHandle session, FilterDefinition<TDocument> filter, CountOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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return _wrappedCollection.CountDocuments(session, CombineFilters(filter), options, cancellationToken);
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}
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public override Task<long> CountDocumentsAsync(FilterDefinition<TDocument> filter, CountOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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return _wrappedCollection.CountDocumentsAsync(CombineFilters(filter), options, cancellationToken);
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}
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public override Task<long> CountDocumentsAsync(IClientSessionHandle session, FilterDefinition<TDocument> filter, CountOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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return _wrappedCollection.CountDocumentsAsync(session, CombineFilters(filter), options, cancellationToken);
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}
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public override IAsyncCursor<TField> Distinct<TField>(FieldDefinition<TDocument, TField> field, FilterDefinition<TDocument> filter, DistinctOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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return _wrappedCollection.Distinct(field, CombineFilters(filter), options, cancellationToken);
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return _wrappedCollection.DistinctAsync(session, field, CombineFilters(filter), options, cancellationToken);
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}
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public override long EstimatedDocumentCount(EstimatedDocumentCountOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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throw new NotSupportedException("EstimatedDocumentCount is not supported for filtered collections.");
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}
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public override Task<long> EstimatedDocumentCountAsync(EstimatedDocumentCountOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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throw new NotSupportedException("EstimatedDocumentCountAsync is not supported for filtered collections.");
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}
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public override IAsyncCursor<TProjection> FindSync<TProjection>(FilterDefinition<TDocument> filter, FindOptions<TDocument, TProjection> options = null, CancellationToken cancellationToken = default(CancellationToken))
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{
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return _wrappedCollection.FindSync(CombineFilters(filter), options, cancellationToken);

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