SERVER-43145 Change M/R output database name to be an optional string

7 files changed, 31 insertions, 29 deletions

diff --git a/src/mongo/db/commands/map_reduce_agg.cpp b/src/mongo/db/commands/map_reduce_agg.cpp
index c94116a3934..6dd26ee46c3 100644
--- a/src/mongo/db/commands/map_reduce_agg.cpp
+++ b/src/mongo/db/commands/map_reduce_agg.cpp
@@ -115,8 +115,8 @@ bool runAggregationMapReduce(OperationContext* opCtx,
                                                        &result);
     else
         map_reduce_output_format::appendOutResponse(
-            NamespaceString(parsedMr.getOutOptions().getDatabaseName(),
-                            parsedMr.getOutOptions().getCollectionName()),
+            parsedMr.getOutOptions().getDatabaseName(),
+            parsedMr.getOutOptions().getCollectionName(),
             boost::get_optional_value_or(parsedMr.getVerbose(), false),
             false,
             &result);
diff --git a/src/mongo/db/commands/map_reduce_out_options.cpp b/src/mongo/db/commands/map_reduce_out_options.cpp
index bbcc069272b..ce82280997a 100644
--- a/src/mongo/db/commands/map_reduce_out_options.cpp
+++ b/src/mongo/db/commands/map_reduce_out_options.cpp
@@ -38,7 +38,7 @@ using namespace std::string_literals;
 
 MapReduceOutOptions MapReduceOutOptions::parseFromBSON(const BSONElement& element) {
     if (element.type() == BSONType::String) {
-        return MapReduceOutOptions("", element.str(), OutputType::Replace, false);
+        return MapReduceOutOptions(boost::none, element.str(), OutputType::Replace, false);
     } else if (element.type() == BSONType::Object) {
         const auto obj = element.embeddedObject();
         // The inline option is allowed alone.
@@ -47,7 +47,7 @@ MapReduceOutOptions MapReduceOutOptions::parseFromBSON(const BSONElement& elemen
             uassert(
                 ErrorCodes::BadValue, "'inline' takes only numeric '1'", inMemory.number() == 1.0);
 
-            return MapReduceOutOptions("", "", OutputType::InMemory, false);
+            return MapReduceOutOptions(boost::none, "", OutputType::InMemory, false);
         }
 
         int allowedNFields = 3;
@@ -64,15 +64,15 @@ MapReduceOutOptions MapReduceOutOptions::parseFromBSON(const BSONElement& elemen
             }
         }();
 
-        const auto databaseName = [&]() {
+        const auto databaseName = [&]() -> boost::optional<std::string> {
             if (const auto db = obj["db"]) {
                 uassert(ErrorCodes::BadValue,
                         "db field value must be string",
                         db.type() == BSONType::String);
-                return db.str();
+                return boost::make_optional(db.str());
             } else {
                 --allowedNFields;
-                return ""s;
+                return boost::none;
             }
         }();
 
diff --git a/src/mongo/db/commands/map_reduce_out_options.h b/src/mongo/db/commands/map_reduce_out_options.h
index 4e99254186a..b7d25fd7840 100644
--- a/src/mongo/db/commands/map_reduce_out_options.h
+++ b/src/mongo/db/commands/map_reduce_out_options.h
@@ -52,7 +52,7 @@ public:
     static MapReduceOutOptions parseFromBSON(const BSONElement& element);
 
     MapReduceOutOptions() = default;
-    MapReduceOutOptions(std::string databaseName,
+    MapReduceOutOptions(boost::optional<std::string> databaseName,
                         std::string collectionName,
                         const OutputType outputType,
                         bool sharded)
@@ -76,8 +76,8 @@ public:
             case OutputType::Reduce:
                 sub.append("reduce", _collectionName);
         }
-        if (_databaseName != "")
-            sub.append("db", _databaseName);
+        if (_databaseName)
+            sub.append("db", _databaseName.get());
         if (_sharded)
             sub.append("sharded", true);
     }
@@ -90,12 +90,12 @@ public:
         return _collectionName;
     }
 
-    const std::string& getDatabaseName() const {
+    const boost::optional<std::string>& getDatabaseName() const {
         return _databaseName;
     }
 
 private:
-    std::string _databaseName;
+    boost::optional<std::string> _databaseName;
     std::string _collectionName;
     OutputType _outputType;
     bool _sharded;
diff --git a/src/mongo/db/query/map_reduce_output_format.cpp b/src/mongo/db/query/map_reduce_output_format.cpp
index c3c9859a423..9747dfa05b6 100644
--- a/src/mongo/db/query/map_reduce_output_format.cpp
+++ b/src/mongo/db/query/map_reduce_output_format.cpp
@@ -76,15 +76,15 @@ void appendInlineResponse(BSONArray&& documents,
     appendMetadataFields(verbose, inMongos, resultBuilder);
 }
 
-void appendOutResponse(NamespaceString outCollNss,
+void appendOutResponse(boost::optional<std::string> outDb,
+                       std::string outColl,
                        bool verbose,
                        bool inMongos,
                        BSONObjBuilder* resultBuilder) {
-    if (outCollNss.db().empty())
-        resultBuilder->append("result", outCollNss.coll());
+    if (!outDb)
+        resultBuilder->append("result", outColl);
     else
-        resultBuilder->append("result",
-                              BSON("db" << outCollNss.db() << "collection" << outCollNss.coll()));
+        resultBuilder->append("result", BSON("db" << *outDb << "collection" << outColl));
     appendMetadataFields(verbose, inMongos, resultBuilder);
 }
 }  // namespace mongo::map_reduce_output_format
diff --git a/src/mongo/db/query/map_reduce_output_format.h b/src/mongo/db/query/map_reduce_output_format.h
index eff91ae14e3..26136efd1f1 100644
--- a/src/mongo/db/query/map_reduce_output_format.h
+++ b/src/mongo/db/query/map_reduce_output_format.h
@@ -50,12 +50,13 @@ void appendInlineResponse(BSONArray&& documents,
 
 /**
  * Appends fields to 'resultBuilder' to formulate a response that would be given if the mapReduce
- * command had written output to the collection named by 'outCollNss'. 'verbose' causes extra fields
- * to be appended to the response in accordance with the verbose option on the mapReduce command.
- * 'inMongos' indicates that we are using the format that was historically sent from mongos. If it
- * isn't set, we will use the mongod format.
+ * command had written output to the collection named by 'outColl' in output database 'outDb'.
+ * 'verbose' causes extra fields to be appended to the response in accordance with the verbose
+ * option on the mapReduce command. 'inMongos' indicates that we are using the format that was
+ * historically sent from mongos. If it isn't set, we will use the mongod format.
  */
-void appendOutResponse(NamespaceString outCollNss,
+void appendOutResponse(boost::optional<std::string> outDb,
+                       std::string outColl,
                        bool verbose,
                        bool inMongos,
                        BSONObjBuilder* resultBuilder);
diff --git a/src/mongo/db/query/map_reduce_output_format_test.cpp b/src/mongo/db/query/map_reduce_output_format_test.cpp
index 06460770eb2..04589b4c2e3 100644
--- a/src/mongo/db/query/map_reduce_output_format_test.cpp
+++ b/src/mongo/db/query/map_reduce_output_format_test.cpp
@@ -36,6 +36,8 @@
 #include "mongo/db/query/map_reduce_output_format.h"
 #include "mongo/unittest/unittest.h"
 
+using namespace std::literals::string_literals;
+
 namespace mongo {
 namespace {
 
@@ -65,7 +67,7 @@ TEST(MapReduceOutputFormat, FormatEmptyInlineMapReduceResponse) {
 
 TEST(MapReduceOutputFormat, FormatNonInlineMapReduceResponseWithoutDb) {
     BSONObjBuilder builder;
-    map_reduce_output_format::appendOutResponse(NamespaceString("", "c"), false, false, &builder);
+    map_reduce_output_format::appendOutResponse(boost::none, "c", false, false, &builder);
     ASSERT_BSONOBJ_EQ(fromjson("{result: \"c\","
                                "timeMillis: 0,"
                                "counts: {input: 0, emit: 0, reduce: 0, output: 0},"
@@ -75,7 +77,7 @@ TEST(MapReduceOutputFormat, FormatNonInlineMapReduceResponseWithoutDb) {
 
 TEST(MapReduceOutputFormat, FormatNonInlineMapReduceResponseWithDb) {
     BSONObjBuilder builder;
-    map_reduce_output_format::appendOutResponse(NamespaceString("db", "c"), false, false, &builder);
+    map_reduce_output_format::appendOutResponse("db"s, "c", false, false, &builder);
     ASSERT_BSONOBJ_EQ(fromjson("{result: {db: \"db\", collection: \"c\"},"
                                "timeMillis: 0,"
                                "counts: {input: 0, emit: 0, reduce: 0, output: 0},"
@@ -85,7 +87,7 @@ TEST(MapReduceOutputFormat, FormatNonInlineMapReduceResponseWithDb) {
 
 TEST(MapReduceOutputFormat, FormatVerboseMapReduceResponse) {
     BSONObjBuilder builder;
-    map_reduce_output_format::appendOutResponse(NamespaceString("", "c"), true, false, &builder);
+    map_reduce_output_format::appendOutResponse(boost::none, "c", true, false, &builder);
     ASSERT_BSONOBJ_EQ(fromjson("{result: \"c\","
                                "timeMillis: 0,"
                                "timing: {mapTime: 0, emitLoop: 0, reduceTime: 0, total: 0},"
@@ -128,7 +130,7 @@ TEST(MapReduceOutputFormat, FormatEmptyInlineClusterMapReduceResponse) {
 
 TEST(MapReduceOutputFormat, FormatNonInlineClusterMapReduceResponseWithoutDb) {
     BSONObjBuilder builder;
-    map_reduce_output_format::appendOutResponse(NamespaceString("", "c"), false, true, &builder);
+    map_reduce_output_format::appendOutResponse(boost::none, "c", false, true, &builder);
     ASSERT_BSONOBJ_EQ(fromjson("{result: \"c\","
                                "counts: {input: 0, emit: 0, reduce: 0, output: 0},"
                                "timeMillis: 0,"
@@ -142,7 +144,7 @@ TEST(MapReduceOutputFormat, FormatNonInlineClusterMapReduceResponseWithoutDb) {
 
 TEST(MapReduceOutputFormat, FormatNonInlineClusterMapReduceResponseWithDb) {
     BSONObjBuilder builder;
-    map_reduce_output_format::appendOutResponse(NamespaceString("db", "c"), false, true, &builder);
+    map_reduce_output_format::appendOutResponse("db"s, "c", false, true, &builder);
     ASSERT_BSONOBJ_EQ(fromjson("{result: {db: \"db\", collection: \"c\"},"
                                "counts: {input: 0, emit: 0, reduce: 0, output: 0},"
                                "timeMillis: 0,"
@@ -156,7 +158,7 @@ TEST(MapReduceOutputFormat, FormatNonInlineClusterMapReduceResponseWithDb) {
 
 TEST(MapReduceOutputFormat, FormatVerboseClusterMapReduceResponse) {
     BSONObjBuilder builder;
-    map_reduce_output_format::appendOutResponse(NamespaceString("", "c"), true, true, &builder);
+    map_reduce_output_format::appendOutResponse(boost::none, "c", true, true, &builder);
     ASSERT_BSONOBJ_EQ(fromjson("{result: \"c\","
                                "counts: {input: 0, emit: 0, reduce: 0, output: 0},"
                                "timeMillis: 0,"
diff --git a/src/mongo/s/commands/cluster_map_reduce_agg.cpp b/src/mongo/s/commands/cluster_map_reduce_agg.cpp
index af2c92807be..e8b433956b7 100644
--- a/src/mongo/s/commands/cluster_map_reduce_agg.cpp
+++ b/src/mongo/s/commands/cluster_map_reduce_agg.cpp
@@ -75,7 +75,6 @@ bool runAggregationMapReduce(OperationContext* opCtx,
     auto mrRequest = MapReduce::parse(IDLParserErrorContext("MapReduce"), cmd);
     bool inMemory = mrRequest.getOutOptions().getOutputType() == OutputType::InMemory;
     std::string outColl = mrRequest.getOutOptions().getCollectionName();
-    std::string outDb = mrRequest.getOutOptions().getDatabaseName();
     // Either inline response specified or we have an output collection.
     invariant(inMemory ^ !outColl.empty());