Core/Database: Optimize named query result field access

2 files changed, 31 insertions, 8 deletions

diff --git a/src/server/database/Database/QueryResult.cpp b/src/server/database/Database/QueryResult.cpp
index 3180761b81f..6edfff80b9c 100644
--- a/src/server/database/Database/QueryResult.cpp
+++ b/src/server/database/Database/QueryResult.cpp
@@ -405,7 +405,7 @@ _fields(fields)
     for (uint32 i = 0; i < _fieldCount; i++)
     {
         InitializeDatabaseFieldMetadata(&_fieldMetadata[i], &_fields[i], i, false);
-        bool success = _fieldIndexByAlias.try_emplace(_fieldMetadata[i].Alias, i).second;
+        bool success = _fieldIndexByAlias.try_emplace({ Trinity::DB::FieldLookupByAliasKey::RuntimeInit, _fieldMetadata[i].Alias }, i).second;
         ASSERT(success);
         _currentRow[i].SetMetadata(&_fieldMetadata[i]);
     }
@@ -463,7 +463,7 @@ m_metadataResult(result)
         rowSize += size;
 
         InitializeDatabaseFieldMetadata(&m_fieldMetadata[i], &field[i], i, true);
-        bool success = m_fieldIndexByAlias.try_emplace(m_fieldMetadata[i].Alias, i).second;
+        bool success = m_fieldIndexByAlias.try_emplace({ Trinity::DB::FieldLookupByAliasKey::RuntimeInit, m_fieldMetadata[i].Alias }, i).second;
         ASSERT(success);
 
         m_rBind[i].buffer_type = field[i].type;
@@ -637,7 +637,7 @@ Field const& ResultSet::operator[](std::size_t index) const
     return _currentRow[index];
 }
 
-Field const& ResultSet::operator[](std::string_view const& alias) const
+Field const& ResultSet::operator[](Trinity::DB::FieldLookupByAliasKey const& alias) const
 {
     auto itr = _fieldIndexByAlias.find(alias);
     ASSERT(itr != _fieldIndexByAlias.end());
@@ -663,7 +663,7 @@ Field const& PreparedResultSet::operator[](std::size_t index) const
     return m_rows[std::size_t(m_rowPosition) * m_fieldCount + index];
 }
 
-Field const& PreparedResultSet::operator[](std::string_view const& alias) const
+Field const& PreparedResultSet::operator[](Trinity::DB::FieldLookupByAliasKey const& alias) const
 {
     ASSERT(m_rowPosition < m_rowCount);
     auto itr = m_fieldIndexByAlias.find(alias);
diff --git a/src/server/database/Database/QueryResult.h b/src/server/database/Database/QueryResult.h
index 381fd9d368c..683f1eeab3c 100644
--- a/src/server/database/Database/QueryResult.h
+++ b/src/server/database/Database/QueryResult.h
@@ -20,9 +20,32 @@
 
 #include "Define.h"
 #include "DatabaseEnvFwd.h"
+#include "Hash.h"
 #include <unordered_map>
 #include <vector>
 
+namespace Trinity::DB
+{
+struct FieldLookupByAliasKey
+{
+    std::size_t HashValue;      ///< Cached hash value (first field to make opeartor== return early, minimizing number of string comparisons)
+    std::string_view Alias;
+
+    // implicit constructor from string literal for users of the query result
+    consteval FieldLookupByAliasKey(char const* alias) : HashValue(HashFnv1a(alias)), Alias(alias) { }
+
+    // runtime only constructor used internally to fill alias to index mapping
+    struct RuntimeInitTag { } static inline constexpr RuntimeInit = { };
+    FieldLookupByAliasKey(RuntimeInitTag, std::string_view alias) : HashValue(HashFnv1a(alias)), Alias(std::move(alias)) { }
+
+    friend bool operator==(FieldLookupByAliasKey const& left, FieldLookupByAliasKey const& right) = default;
+
+    struct Hash { constexpr std::size_t operator()(FieldLookupByAliasKey const& k) const { return k.HashValue; } };
+};
+
+using FieldAliasToIndexMap = std::unordered_map<FieldLookupByAliasKey, std::size_t, FieldLookupByAliasKey::Hash>;
+}
+
 class TC_DATABASE_API ResultSet
 {
     public:
@@ -35,13 +58,13 @@ class TC_DATABASE_API ResultSet
 
         Field* Fetch() const { return _currentRow; }
         Field const& operator[](std::size_t index) const;
-        Field const& operator[](std::string_view const& alias) const;
+        Field const& operator[](Trinity::DB::FieldLookupByAliasKey const& alias) const;
 
         QueryResultFieldMetadata const& GetFieldMetadata(std::size_t index) const;
 
     protected:
         std::vector<QueryResultFieldMetadata> _fieldMetadata;
-        std::unordered_map<std::string_view, std::size_t> _fieldIndexByAlias;
+        Trinity::DB::FieldAliasToIndexMap _fieldIndexByAlias;
         uint64 _rowCount;
         Field* _currentRow;
         uint32 _fieldCount;
@@ -67,13 +90,13 @@ class TC_DATABASE_API PreparedResultSet
 
         Field* Fetch() const;
         Field const& operator[](std::size_t index) const;
-        Field const& operator[](std::string_view const& alias) const;
+        Field const& operator[](Trinity::DB::FieldLookupByAliasKey const& alias) const;
 
         QueryResultFieldMetadata const& GetFieldMetadata(std::size_t index) const;
 
     protected:
         std::vector<QueryResultFieldMetadata> m_fieldMetadata;
-        std::unordered_map<std::string_view, std::size_t> m_fieldIndexByAlias;
+        Trinity::DB::FieldAliasToIndexMap m_fieldIndexByAlias;
         std::vector<Field> m_rows;
         uint64 m_rowCount;
         uint64 m_rowPosition;