CSHARP-580: command based helper methods in MongoCollection should us…

…e the collection's ReadPreference.

Driver/Core/MongoCollection.cs

@@ -38,6 +38,7 @@ public abstract class MongoCollection
         // private fields
         private MongoServer _server;
         private MongoDatabase _database;
+        private MongoDatabase _commandDatabase; // used to run commands with this collection's settings
         private MongoCollectionSettings _settings;
         private string _name;
 
@@ -67,6 +68,21 @@ protected MongoCollection(MongoDatabase database, MongoCollectionSettings settin
             _database = database;
             _settings = settings.FrozenCopy();
             _name = settings.CollectionName;
+
+            // note: if the settings are compatible _commandDatabase will end up being the same instance as _database
+            // need to check for $cmd to avoid infinite recursion
+            if (_name != "$cmd")
+            {
+                var commandDatabaseSettings = _database.Settings.Clone();
+                commandDatabaseSettings.GuidRepresentation = _settings.GuidRepresentation;
+                commandDatabaseSettings.ReadPreference = _settings.ReadPreference;
+                commandDatabaseSettings.SafeMode = _settings.SafeMode; // not really relevant to commands since they are all queries anyway
+                _commandDatabase = _server.GetDatabase(commandDatabaseSettings);
+            }
+            else
+            {
+                _commandDatabase = _database;
+            }
         }
 
         // public properties
@@ -121,7 +137,7 @@ public virtual AggregateResult Aggregate(IEnumerable<BsonDocument> operations)
                 { "aggregate", _name },
                 { "pipeline", pipeline }
             };
-            return _database.RunCommandAs<AggregateResult>(aggregateCommand);
+            return _commandDatabase.RunCommandAs<AggregateResult>(aggregateCommand);
         }
 
         /// <summary>
@@ -155,7 +171,7 @@ public virtual long Count(IMongoQuery query)
                 { "count", _name },
                 { "query", BsonDocumentWrapper.Create(query), query != null } // query is optional
             };
-            var result = _database.RunCommand(command);
+            var result = _commandDatabase.RunCommand(command);
             return result.Response["n"].ToInt64();
         }
 
@@ -231,7 +247,7 @@ public virtual IEnumerable<BsonValue> Distinct(string key, IMongoQuery query)
                 { "key", key },
                 { "query", BsonDocumentWrapper.Create(query), query != null } // query is optional
             };
-            var result = _database.RunCommand(command);
+            var result = _commandDatabase.RunCommand(command);
             return result.Response["values"].AsBsonArray;
         }
 
@@ -298,7 +314,7 @@ public virtual CommandResult DropIndexByName(string indexName)
             };
             try
             {
-                return _database.RunCommand(command);
+                return _commandDatabase.RunCommand(command);
             }
             catch (MongoCommandException ex)
             {
@@ -457,7 +473,7 @@ public virtual FindAndModifyResult FindAndModify(
             };
             try
             {
-                return _database.RunCommandAs<FindAndModifyResult>(command);
+                return _commandDatabase.RunCommandAs<FindAndModifyResult>(command);
             }
             catch (MongoCommandException ex)
             {
@@ -494,7 +510,7 @@ public virtual FindAndModifyResult FindAndRemove(IMongoQuery query, IMongoSortBy
             };
             try
             {
-                return _database.RunCommandAs<FindAndModifyResult>(command);
+                return _commandDatabase.RunCommandAs<FindAndModifyResult>(command);
             }
             catch (MongoCommandException ex)
             {
@@ -638,7 +654,7 @@ public virtual GeoHaystackSearchResult GeoHaystackSearchAs(
             command.Merge(options.ToBsonDocument());
             var geoHaystackSearchResultDefinition = typeof(GeoHaystackSearchResult<>);
             var geoHaystackSearchResultType = geoHaystackSearchResultDefinition.MakeGenericType(documentType);
-            return (GeoHaystackSearchResult)_database.RunCommandAs(geoHaystackSearchResultType, command);
+            return (GeoHaystackSearchResult)_commandDatabase.RunCommandAs(geoHaystackSearchResultType, command);
         }
 
         /// <summary>
@@ -684,7 +700,7 @@ public virtual GeoNearResult<TDocument> GeoNearAs<TDocument>(
                 { "query", BsonDocumentWrapper.Create(query), query != null } // query is optional
             };
             command.Merge(options.ToBsonDocument());
-            return _database.RunCommandAs<GeoNearResult<TDocument>>(command);
+            return _commandDatabase.RunCommandAs<GeoNearResult<TDocument>>(command);
         }
 
         /// <summary>
@@ -729,7 +745,7 @@ public virtual GeoNearResult GeoNearAs(
             command.Merge(options.ToBsonDocument());
             var geoNearResultDefinition = typeof(GeoNearResult<>);
             var geoNearResultType = geoNearResultDefinition.MakeGenericType(documentType);
-            return (GeoNearResult)_database.RunCommandAs(geoNearResultType, command);
+            return (GeoNearResult)_commandDatabase.RunCommandAs(geoNearResultType, command);
         }
 
         /// <summary>
@@ -750,7 +766,7 @@ public virtual GetIndexesResult GetIndexes()
         public virtual CollectionStatsResult GetStats()
         {
             var command = new CommandDocument("collstats", _name);
-            return _database.RunCommandAs<CollectionStatsResult>(command);
+            return _commandDatabase.RunCommandAs<CollectionStatsResult>(command);
         }
 
         /// <summary>
@@ -828,7 +844,7 @@ public virtual IEnumerable<BsonDocument> Group(
                     }
                 }
             };
-            var result = _database.RunCommand(command);
+            var result = _commandDatabase.RunCommand(command);
             return result.Response["retval"].AsBsonArray.Values.Cast<BsonDocument>();
         }
 
@@ -875,7 +891,7 @@ public virtual IEnumerable<BsonDocument> Group(
                     }
                 }
             };
-            var result = _database.RunCommand(command);
+            var result = _commandDatabase.RunCommand(command);
             return result.Response["retval"].AsBsonArray.Values.Cast<BsonDocument>();
         }
 
@@ -1203,7 +1219,7 @@ public virtual MapReduceResult MapReduce(
                 { "reduce", reduce }
             };
             command.Add(options.ToBsonDocument());
-            var result = _database.RunCommandAs<MapReduceResult>(command);
+            var result = _commandDatabase.RunCommandAs<MapReduceResult>(command);
             result.SetInputDatabase(_database);
             return result;
         }
@@ -1259,7 +1275,7 @@ public virtual MapReduceResult MapReduce(BsonJavaScript map, BsonJavaScript redu
         public virtual CommandResult ReIndex()
         {
             var command = new CommandDocument("reIndex", _name);
-            return _database.RunCommand(command);
+            return _commandDatabase.RunCommand(command);
         }
 
         /// <summary>
@@ -1604,7 +1620,7 @@ public virtual SafeModeResult Update(
         public virtual ValidateCollectionResult Validate()
         {
             var command = new CommandDocument("validate", _name);
-            return _database.RunCommandAs<ValidateCollectionResult>(command);
+            return _commandDatabase.RunCommandAs<ValidateCollectionResult>(command);
         }
 
         // internal methods