extract functions to own file

table.h

@@ -10,8 +10,6 @@
 
 namespace usql {
 
-using IndexValue=std::variant<long, std::string>;
-
 struct Table {
 	Table(const Table &other);
 	Table(const std::string& name, const std::vector<ColDefNode>& columns);
@@ -75,7 +73,7 @@ struct Table {
 			bool	m_use_rowids;
 			Table *	m_table;
 			std::vector<Row>::iterator	m_fscan_itr;
-			std::vector<rowid_t>		m_rowids;		// TODO long here
+			std::vector<rowid_t>		m_rowids;
 			size_t						m_rowids_idx{};
 	};