Add missing const qualifier in DatabaseEngine methods

src/database/connection.cpp

@@ -6,8 +6,10 @@ namespace huadb {
 
 Connection::Connection(DatabaseEngine &database) : database_(database) {}
 
-void Connection::SendQuery(const std::string &sql, ResultWriter &writer) { database_.ExecuteSql(sql, writer, *this); }
+void Connection::SendQuery(const std::string &sql, ResultWriter &writer) const {
+  database_.ExecuteSql(sql, writer, *this);
+}
 
-bool Connection::InTransaction() { return database_.InTransaction(*this); }
+bool Connection::InTransaction() const { return database_.InTransaction(*this); }
 
 }  // namespace huadb

src/database/connection.h

@@ -10,8 +10,8 @@ class DatabaseEngine;
 class Connection {
  public:
   explicit Connection(DatabaseEngine &database);
-  void SendQuery(const std::string &sql, ResultWriter &writer);
-  bool InTransaction();
+  void SendQuery(const std::string &sql, ResultWriter &writer) const;
+  bool InTransaction() const;
 
  private:
   DatabaseEngine &database_;

src/database/database_engine.cpp

@@ -70,9 +70,11 @@ DatabaseEngine::~DatabaseEngine() {
 
 const std::string &DatabaseEngine::GetCurrentDatabase() const { return current_db_; }
 
-bool DatabaseEngine::InTransaction(Connection &connection) const { return xids_.find(&connection) != xids_.end(); }
+bool DatabaseEngine::InTransaction(const Connection &connection) const {
+  return xids_.find(&connection) != xids_.end();
+}
 
-void DatabaseEngine::ExecuteSql(const std::string &sql, ResultWriter &writer, Connection &connection) {
+void DatabaseEngine::ExecuteSql(const std::string &sql, ResultWriter &writer, const Connection &connection) {
   if (!sql.empty() && sql[0] == '\\') {
     if (sql[1] == 'l') {
       ShowDatabases(writer);
@@ -285,7 +287,7 @@ void DatabaseEngine::Crash() {
   crashed_ = true;
 }
 
-void DatabaseEngine::Help(ResultWriter &writer) {
+void DatabaseEngine::Help(ResultWriter &writer) const {
   std::string help = R"(
   \? or \h              show help message
   \c [database_name]    change database
@@ -302,7 +304,7 @@ void DatabaseEngine::CreateDatabase(const std::string &db_name, bool exists_ok,
   WriteOneCell("CREATE DATABASE", writer);
 }
 
-void DatabaseEngine::ShowDatabases(ResultWriter &writer) {
+void DatabaseEngine::ShowDatabases(ResultWriter &writer) const {
   writer.BeginTable();
   writer.BeginHeader();
   writer.WriteHeaderCell("database_name");
@@ -349,7 +351,7 @@ void DatabaseEngine::CreateTable(const std::string &table_name, const ColumnList
   WriteOneCell("CREATE TABLE", writer);
 }
 
-void DatabaseEngine::DescribeTable(const std::string &table_name, ResultWriter &writer) {
+void DatabaseEngine::DescribeTable(const std::string &table_name, ResultWriter &writer) const {
   auto column_list = catalog_->GetTableColumnList(table_name);
   writer.BeginTable();
   writer.BeginHeader();
@@ -370,7 +372,7 @@ void DatabaseEngine::DescribeTable(const std::string &table_name, ResultWriter &
   writer.WriteRowCount(column_count);
 }
 
-void DatabaseEngine::ShowTables(ResultWriter &writer) {
+void DatabaseEngine::ShowTables(ResultWriter &writer) const {
   writer.BeginTable();
   writer.BeginHeader();
   writer.WriteHeaderCell("table_name");
@@ -402,7 +404,7 @@ void DatabaseEngine::DropIndex(const std::string &index_name, ResultWriter &writ
   WriteOneCell("DROP INDEX", writer);
 }
 
-void DatabaseEngine::Begin(Connection &connection) {
+void DatabaseEngine::Begin(const Connection &connection) {
   if (xids_.find(&connection) != xids_.end()) {
     throw DbException("There is already a transaction in progress");
   } else {
@@ -412,7 +414,7 @@ void DatabaseEngine::Begin(Connection &connection) {
   }
 }
 
-void DatabaseEngine::Commit(Connection &connection) {
+void DatabaseEngine::Commit(const Connection &connection) {
   if (xids_.find(&connection) == xids_.end()) {
     throw DbException("There is no transaction in process");
   } else {
@@ -422,7 +424,7 @@ void DatabaseEngine::Commit(Connection &connection) {
   }
 }
 
-void DatabaseEngine::Rollback(Connection &connection) {
+void DatabaseEngine::Rollback(const Connection &connection) {
   if (xids_.find(&connection) == xids_.end()) {
     throw DbException("There is no transaction in process");
   } else {
@@ -496,7 +498,7 @@ void DatabaseEngine::VariableSet(const Connection &connection, const VariableSet
 }
 
 void DatabaseEngine::VariableShow(const Connection &connection, const VariableShowStatement &stmt,
-                                  ResultWriter &writer) {
+                                  ResultWriter &writer) const {
   std::string result;
   if (stmt.variable_ == "tables") {
     ShowTables(writer);
@@ -510,10 +512,10 @@ void DatabaseEngine::VariableShow(const Connection &connection, const VariableSh
     result = std::to_string(log_manager_->GetRedoCount());
   } else {
     if (client_variables_.find(&connection) == client_variables_.end() ||
-        client_variables_[&connection].find(stmt.variable_) == client_variables_[&connection].end()) {
+        client_variables_.at(&connection).find(stmt.variable_) == client_variables_.at(&connection).end()) {
       throw DbException("Variable not found");
     }
-    result = client_variables_[&connection][stmt.variable_];
+    result = client_variables_.at(&connection).at(stmt.variable_);
   }
   writer.BeginTable();
   writer.BeginHeader();

src/database/database_engine.h

@@ -33,32 +33,32 @@ class DatabaseEngine {
   ~DatabaseEngine();
 
   const std::string &GetCurrentDatabase() const;
-  bool InTransaction(Connection &connection) const;
-  void ExecuteSql(const std::string &sql, ResultWriter &writer, Connection &connection);
+  bool InTransaction(const Connection &connection) const;
+  void ExecuteSql(const std::string &sql, ResultWriter &writer, const Connection &connection);
 
   void Crash();
 
  private:
-  void Help(ResultWriter &writer);
+  void Help(ResultWriter &writer) const;
 
   void CreateDatabase(const std::string &db_name, bool exists_ok, ResultWriter &writer);
-  void ShowDatabases(ResultWriter &writer);
+  void ShowDatabases(ResultWriter &writer) const;
   void ChangeDatabase(const std::string &db_name, ResultWriter &writer);
   void DropDatabase(const std::string &db_name, bool missing_ok, ResultWriter &writer);
   void CloseDatabase();
 
   void CreateTable(const std::string &table_name, const ColumnList &column_list, ResultWriter &writer);
-  void DescribeTable(const std::string &table_name, ResultWriter &writer);
-  void ShowTables(ResultWriter &writer);
+  void DescribeTable(const std::string &table_name, ResultWriter &writer) const;
+  void ShowTables(ResultWriter &writer) const;
   void DropTable(const std::string &table_name, ResultWriter &writer);
 
   void CreateIndex(const std::string &index_name, const std::string &table_name,
                    const std::vector<std::string> &column_names, ResultWriter &writer);
   void DropIndex(const std::string &index_name, ResultWriter &writer);
 
-  void Begin(Connection &connection);
-  void Commit(Connection &connection);
-  void Rollback(Connection &connection);
+  void Begin(const Connection &connection);
+  void Commit(const Connection &connection);
+  void Rollback(const Connection &connection);
 
   void Checkpoint();
   void Recover();
@@ -67,7 +67,7 @@ class DatabaseEngine {
   void Lock(xid_t xid, const LockStatement &stmt, ResultWriter &writer);
 
   void VariableSet(const Connection &connection, const VariableSetStatement &stmt, ResultWriter &writer);
-  void VariableShow(const Connection &connection, const VariableShowStatement &stmt, ResultWriter &writer);
+  void VariableShow(const Connection &connection, const VariableShowStatement &stmt, ResultWriter &writer) const;
 
   void Analyze(const AnalyzeStatement &stmt, ResultWriter &writer);
   void Vacuum(const VacuumStatement &stmt, ResultWriter &writer);
@@ -90,9 +90,9 @@ class DatabaseEngine {
   std::unique_ptr<LockManager> lock_manager_;
 
   std::unordered_map<const Connection *, std::unordered_map<std::string, std::string>> client_variables_;
-  std::unordered_map<Connection *, xid_t> xids_;
+  std::unordered_map<const Connection *, xid_t> xids_;
   std::unordered_map<const Connection *, IsolationLevel> isolation_levels_;
-  std::unordered_set<Connection *> auto_transaction_set_;
+  std::unordered_set<const Connection *> auto_transaction_set_;
 
   ForceJoin force_join_ = ForceJoin::NONE;
   JoinOrderAlgorithm join_order_algorithm_ = DEFAULT_JOIN_ORDER_ALGORITHM;