SERVER-55058 More move optimizations for Document/Value

13 files changed, 106 insertions, 15 deletions

diff --git a/src/mongo/db/exec/document_value/document.cpp b/src/mongo/db/exec/document_value/document.cpp
index f9c37fb91ac..9e639d321ff 100644
--- a/src/mongo/db/exec/document_value/document.cpp
+++ b/src/mongo/db/exec/document_value/document.cpp
@@ -518,7 +518,7 @@ Document Document::fromBsonWithMetaData(const BSONObj& bson) {
     return md.freeze();
 }
 
-Document Document::getOwned() const {
+Document Document::getOwned() const& {
     if (isOwned()) {
         return *this;
     } else {
@@ -528,6 +528,16 @@ Document Document::getOwned() const {
     }
 }
 
+Document Document::getOwned() && {
+    if (isOwned()) {
+        return std::move(*this);
+    } else {
+        MutableDocument md(std::move(*this));
+        md.makeOwned();
+        return md.freeze();
+    }
+}
+
 MutableDocument::MutableDocument(size_t expectedFields)
     : _storageHolder(nullptr), _storage(_storageHolder) {
     if (expectedFields) {
diff --git a/src/mongo/db/exec/document_value/document.h b/src/mongo/db/exec/document_value/document.h
index 439c88f1cc2..526fa10eb60 100644
--- a/src/mongo/db/exec/document_value/document.h
+++ b/src/mongo/db/exec/document_value/document.h
@@ -311,7 +311,8 @@ public:
     /**
      * Returns a document that owns the underlying BSONObj.
      */
-    Document getOwned() const;
+    Document getOwned() const&;
+    Document getOwned() &&;
 
     /**
      * Returns true if the underlying BSONObj is owned.
@@ -515,6 +516,10 @@ public:
         storage().appendField(fieldName, ValueElement::Kind::kInserted) = val;
     }
 
+    void addField(StringData fieldName, Value&& val) {
+        storage().appendField(fieldName, ValueElement::Kind::kInserted) = std::move(val);
+    }
+
     /** Update field by key. If there is no field with that key, add one.
      *
      *  If the new value is missing(), the field is logically removed.
@@ -525,6 +530,9 @@ public:
     void setField(StringData key, const Value& val) {
         getField(key) = val;
     }
+    void setField(StringData key, Value&& val) {
+        getField(key) = std::move(val);
+    }
     MutableValue getField(StringData key) {
         return MutableValue(storage().getField(key, DocumentStorage::LookupPolicy::kCacheOnly));
     }
@@ -539,6 +547,9 @@ public:
     void setField(Position pos, const Value& val) {
         getField(pos) = val;
     }
+    void setField(Position pos, Value&& val) {
+        getField(pos) = std::move(val);
+    }
     MutableValue getField(Position pos) {
         return MutableValue(storage().getField(pos).val);
     }
@@ -561,12 +572,18 @@ public:
     void setNestedField(const FieldPath& dottedField, const Value& val) {
         getNestedField(dottedField) = val;
     }
+    void setNestedField(const FieldPath& dottedField, Value&& val) {
+        getNestedField(dottedField) = std::move(val);
+    }
 
     /// Takes positions vector from Document::getNestedField. All fields in path must exist.
     MutableValue getNestedField(const std::vector<Position>& positions);
     void setNestedField(const std::vector<Position>& positions, const Value& val) {
         getNestedField(positions) = val;
     }
+    void setNestedField(const std::vector<Position>& positions, Value&& val) {
+        getNestedField(positions) = std::move(val);
+    }
 
     /**
      * Copies all metadata from source if it has any.
diff --git a/src/mongo/db/exec/document_value/document_value_test.cpp b/src/mongo/db/exec/document_value/document_value_test.cpp
index 6ca845670a3..421da707001 100644
--- a/src/mongo/db/exec/document_value/document_value_test.cpp
+++ b/src/mongo/db/exec/document_value/document_value_test.cpp
@@ -372,6 +372,23 @@ public:
         Document final = md.freeze();
         ASSERT_EQUALS(3ULL, final.computeSize());
         assertRoundTrips(final);
+
+        // Add field to the document as an lvalue.
+        MutableDocument md1;
+        Value v1(1);
+        md1.addField("a", v1);
+        ASSERT_VALUE_EQ(md1.peek().getField("a"), v1);
+
+        // Set field to the document as an lvalue.
+        Value v2(2);
+        md1.setField("a", v2);
+        ASSERT_VALUE_EQ(md1.peek().getField("a"), v2);
+
+        // Set nested field to the document as an lvalue.
+        FieldPath xxyyzz("xx.yy.zz");
+        Value v3("nested"_sd);
+        md1.setNestedField(xxyyzz, v3);
+        ASSERT_VALUE_EQ(md1.peek().getNestedField(xxyyzz), v3);
     }
 };
 
@@ -1157,6 +1174,17 @@ public:
         ASSERT_EQUALS(-.3, document["banana"].getDouble());
         ASSERT_EQUALS(Object, value.getType());
         assertRoundTrips(value);
+
+        MutableDocument md1;
+        Value v(1);
+        md1.addField("a", v);
+
+        MutableDocument md2;
+        // Construct Value from an rvalue.
+        md2.addField("nested", Value(md1.freeze()));
+
+        ASSERT_VALUE_EQ(md2.peek().getNestedField("nested.a"), v);
+        ASSERT_DOCUMENT_EQ(md1.freeze(), mongo::Document());
     }
 };
 
diff --git a/src/mongo/db/exec/document_value/value.cpp b/src/mongo/db/exec/document_value/value.cpp
index f69bdb313f0..29e5680a303 100644
--- a/src/mongo/db/exec/document_value/value.cpp
+++ b/src/mongo/db/exec/document_value/value.cpp
@@ -131,6 +131,10 @@ void ValueStorage::putDocument(const Document& d) {
     putRefCountable(d._storage);
 }
 
+void ValueStorage::putDocument(Document&& d) {
+    putRefCountable(std::move(d._storage));
+}
+
 void ValueStorage::putVector(boost::intrusive_ptr<RCVector>&& vec) {
     fassert(16485, bool(vec));
     putRefCountable(std::move(vec));
@@ -159,7 +163,14 @@ Document ValueStorage::getDocument() const {
 
 // not in header because document is fwd declared
 Value::Value(const BSONObj& obj) : _storage(Object, Document(obj.getOwned())) {}
+
+// An option of providing 'Value(Document)' was rejected in favor of 'Value(const Document&)' and
+// 'Value(Document&&)' overloads, and lvalue/rvalue reference overloads of callees, since
+// 'Value(Document)' option with a lvalue parameter would result in one extra move operation in
+// 'ValueStorage::putDocument()'.
 Value::Value(const Document& doc) : _storage(Object, doc.isOwned() ? doc : doc.getOwned()) {}
+Value::Value(Document&& doc)
+    : _storage(Object, doc.isOwned() ? std::move(doc) : std::move(doc).getOwned()) {}
 
 Value::Value(const BSONElement& elem) : _storage(elem.type()) {
     switch (elem.type()) {
diff --git a/src/mongo/db/exec/document_value/value.h b/src/mongo/db/exec/document_value/value.h
index 072ff9e0a18..c89fedcf092 100644
--- a/src/mongo/db/exec/document_value/value.h
+++ b/src/mongo/db/exec/document_value/value.h
@@ -32,6 +32,7 @@
 #include "mongo/base/static_assert.h"
 #include "mongo/base/string_data.h"
 #include "mongo/db/exec/document_value/value_internal.h"
+#include "mongo/util/concepts.h"
 #include "mongo/util/uuid.h"
 
 namespace mongo {
@@ -102,6 +103,7 @@ public:
     explicit Value(StringData value) : _storage(String, value) {}
     explicit Value(const std::string& value) : _storage(String, StringData(value)) {}
     explicit Value(const Document& doc);
+    explicit Value(Document&& doc);
     explicit Value(const BSONObj& obj);
     explicit Value(const BSONArray& arr);
     explicit Value(const std::vector<BSONObj>& vec);
@@ -128,6 +130,11 @@ public:
      */
     explicit Value(const char*) = delete;
 
+    Value(const Value&) = default;
+    Value(Value&&) = default;
+    Value& operator=(const Value&) = default;
+    Value& operator=(Value&&) = default;
+
     /**
      *  Prevent implicit conversions to the accepted argument types.
      */
@@ -397,14 +404,22 @@ inline void swap(mongo::Value& lhs, mongo::Value& rhs) {
     lhs.swap(rhs);
 }
 
+MONGO_MAKE_BOOL_TRAIT(CanConstructValueFrom,
+                      (typename T),
+                      (T),
+                      (T val),
+                      //
+                      Value(std::forward<T>(val)));
+
 /**
  * This class is identical to Value, but supports implicit creation from any of the types explicitly
  * supported by Value.
  */
 class ImplicitValue : public Value {
 public:
-    template <typename T>
-    ImplicitValue(T arg) : Value(std::move(arg)) {}
+    TEMPLATE(typename T)
+    REQUIRES(CanConstructValueFrom<T>)
+    ImplicitValue(T&& arg) : Value(std::forward<T>(arg)) {}
 
     ImplicitValue(std::initializer_list<ImplicitValue> values) : Value(convertToValues(values)) {}
 
@@ -412,6 +427,7 @@ public:
 
     static std::vector<Value> convertToValues(const std::vector<int>& vec) {
         std::vector<Value> values;
+        values.reserve(vec.size());
         for_each(vec.begin(), vec.end(), ([&](const int& val) { values.emplace_back(val); }));
         return values;
     }
@@ -421,6 +437,7 @@ public:
      */
     static Value convertToValue(const std::vector<ImplicitValue>& vec) {
         std::vector<Value> values;
+        values.reserve(vec.size());
         for_each(
             vec.begin(), vec.end(), ([&](const ImplicitValue& val) { values.push_back(val); }));
         return Value(values);
@@ -431,6 +448,7 @@ public:
      */
     static std::vector<Value> convertToValues(const std::vector<ImplicitValue>& list) {
         std::vector<Value> values;
+        values.reserve(list.size());
         for (const ImplicitValue& val : list) {
             values.push_back(val);
         }
diff --git a/src/mongo/db/exec/document_value/value_internal.h b/src/mongo/db/exec/document_value/value_internal.h
index 19bded8ea42..b19af0e728f 100644
--- a/src/mongo/db/exec/document_value/value_internal.h
+++ b/src/mongo/db/exec/document_value/value_internal.h
@@ -123,6 +123,11 @@ public:
         type = t;
         putDocument(d);
     }
+    ValueStorage(BSONType t, Document&& d) {
+        zero();
+        type = t;
+        putDocument(std::move(d));
+    }
     ValueStorage(BSONType t, boost::intrusive_ptr<RCVector>&& a) {
         zero();
         type = t;
@@ -228,6 +233,7 @@ public:
     void putString(StringData s);
     void putVector(boost::intrusive_ptr<RCVector>&& v);
     void putDocument(const Document& d);
+    void putDocument(Document&& d);
     void putRegEx(const BSONRegEx& re);
     void putBinData(const BSONBinData& bd) {
         putRefCountable(RCString::create(StringData(static_cast<const char*>(bd.data), bd.length)));
diff --git a/src/mongo/db/exec/projection_executor_utils.cpp b/src/mongo/db/exec/projection_executor_utils.cpp
index 1cbc04531c9..b77b330ff05 100644
--- a/src/mongo/db/exec/projection_executor_utils.cpp
+++ b/src/mongo/db/exec/projection_executor_utils.cpp
@@ -180,7 +180,7 @@ Value applyFindSliceProjectionHelper(const Document& input,
     }
 
     MutableDocument output(input);
-    output.setField(fieldName, val);
+    output.setField(fieldName, std::move(val));
     return Value{output.freeze()};
 }
 }  // namespace
diff --git a/src/mongo/db/pipeline/accumulator_js_reduce.cpp b/src/mongo/db/pipeline/accumulator_js_reduce.cpp
index fcc01b061bd..e7192465d7c 100644
--- a/src/mongo/db/pipeline/accumulator_js_reduce.cpp
+++ b/src/mongo/db/pipeline/accumulator_js_reduce.cpp
@@ -165,7 +165,7 @@ Value AccumulatorInternalJsReduce::getValue(bool toBeMerged) {
     if (toBeMerged) {
         MutableDocument output;
         output.addField("k", _key);
-        output.addField("v", result);
+        output.addField("v", std::move(result));
         return Value(output.freeze());
     } else {
         return result;
diff --git a/src/mongo/db/pipeline/accumulator_merge_objects.cpp b/src/mongo/db/pipeline/accumulator_merge_objects.cpp
index 5eb03eed74b..8804a8a0f05 100644
--- a/src/mongo/db/pipeline/accumulator_merge_objects.cpp
+++ b/src/mongo/db/pipeline/accumulator_merge_objects.cpp
@@ -80,7 +80,7 @@ void AccumulatorMergeObjects::processInternal(const Value& input, bool merging)
         if (pair.second.missing())
             continue;
 
-        _output.setField(pair.first, pair.second);
+        _output.setField(pair.first, std::move(pair.second));
     }
     _memUsageBytes = sizeof(*this) + _output.getApproximateSize();
 }
diff --git a/src/mongo/db/pipeline/document_source_change_stream_transform.cpp b/src/mongo/db/pipeline/document_source_change_stream_transform.cpp
index 1eb9611f2c8..fcb3d898a3c 100644
--- a/src/mongo/db/pipeline/document_source_change_stream_transform.cpp
+++ b/src/mongo/db/pipeline/document_source_change_stream_transform.cpp
@@ -361,21 +361,22 @@ Document DocumentSourceChangeStreamTransform::applyTransformation(const Document
     }
 
     // Add the post-image, pre-image, namespace, documentKey and other fields as appropriate.
-    doc.addField(DocumentSourceChangeStream::kFullDocumentField, fullDocument);
+    doc.addField(DocumentSourceChangeStream::kFullDocumentField, std::move(fullDocument));
     if (_includePreImageOptime) {
         // Set 'kFullDocumentBeforeChangeField' to the pre-image optime. The DSCSLookupPreImage
         // stage will replace this optime with the actual pre-image taken from the oplog.
-        doc.addField(DocumentSourceChangeStream::kFullDocumentBeforeChangeField, preImageOpTime);
+        doc.addField(DocumentSourceChangeStream::kFullDocumentBeforeChangeField,
+                     std::move(preImageOpTime));
     }
     doc.addField(DocumentSourceChangeStream::kNamespaceField,
                  operationType == DocumentSourceChangeStream::kDropDatabaseOpType
                      ? Value(Document{{"db", nss.db()}})
                      : Value(Document{{"db", nss.db()}, {"coll", nss.coll()}}));
-    doc.addField(DocumentSourceChangeStream::kDocumentKeyField, documentKey);
+    doc.addField(DocumentSourceChangeStream::kDocumentKeyField, std::move(documentKey));
 
     // Note that 'updateDescription' might be the 'missing' value, in which case it will not be
     // serialized.
-    doc.addField("updateDescription", updateDescription);
+    doc.addField("updateDescription", std::move(updateDescription));
     return doc.freeze();
 }
 
diff --git a/src/mongo/db/pipeline/document_source_group.cpp b/src/mongo/db/pipeline/document_source_group.cpp
index c4ca7bc932f..a92a05386c5 100644
--- a/src/mongo/db/pipeline/document_source_group.cpp
+++ b/src/mongo/db/pipeline/document_source_group.cpp
@@ -749,7 +749,7 @@ Document DocumentSourceGroup::makeDocument(const Value& id,
             // we return null in this case so return objects are predictable
             out.addField(_accumulatedFields[i].fieldName, Value(BSONNULL));
         } else {
-            out.addField(_accumulatedFields[i].fieldName, val);
+            out.addField(_accumulatedFields[i].fieldName, std::move(val));
         }
     }
 
diff --git a/src/mongo/db/pipeline/document_source_redact.cpp b/src/mongo/db/pipeline/document_source_redact.cpp
index 8fcc1a6c826..eaefcdf672b 100644
--- a/src/mongo/db/pipeline/document_source_redact.cpp
+++ b/src/mongo/db/pipeline/document_source_redact.cpp
@@ -150,9 +150,9 @@ boost::optional<Document> DocumentSourceRedact::redactObject(const Document& roo
             const Document::FieldPair field(fields.next());
 
             // This changes CURRENT so don't read from variables after this
-            const Value val = redactValue(field.second, root);
+            Value val = redactValue(field.second, root);
             if (!val.missing()) {
-                out.addField(field.first, val);
+                out.addField(field.first, std::move(val));
             }
         }
         return out.freeze();
diff --git a/src/mongo/db/pipeline/expression.cpp b/src/mongo/db/pipeline/expression.cpp
index 4746d3a253c..7a8fa4ec464 100644
--- a/src/mongo/db/pipeline/expression.cpp
+++ b/src/mongo/db/pipeline/expression.cpp
@@ -655,7 +655,7 @@ Value ExpressionObjectToArray::evaluate(const Document& root, Variables* variabl
         Document::FieldPair pair = iter.next();
         MutableDocument keyvalue;
         keyvalue.addField("k", Value(pair.first));
-        keyvalue.addField("v", pair.second);
+        keyvalue.addField("v", std::move(pair.second));
         output.push_back(keyvalue.freezeToValue());
     }