use Field instead of FieldDesc in select_stmt

src/observer/sql/executor/execute_stage.cpp

@@ -266,8 +266,8 @@ RC ExecuteStage::do_select(SQLStageEvent *sql_event)
   pred_oper.add_child(&table_scan_operator);
   ProjectOperator project_oper;
   project_oper.add_child(&pred_oper);
-  for (const FieldDesc &field : select_stmt->query_fields()) {
-    project_oper.add_projection(field.table_, field.field_meta_);
+  for (const Field &field : select_stmt->query_fields()) {
+    project_oper.add_projection(field.table(), field.meta());
   }
   rc = project_oper.open();
   if (rc != RC::SUCCESS) {

src/observer/sql/operator/project_operator.h

@@ -25,7 +25,7 @@ public:
 
   virtual ~ProjectOperator() = default;
 
-  void add_projection(const Table *table, const FieldMeta *field); // TODO how to handle the memory in tupleCellSpec?
+  void add_projection(const Table *table, const FieldMeta *field);
 
   RC open() override;
   RC next() override;

src/observer/sql/stmt/select_stmt.cpp

@@ -27,12 +27,12 @@ SelectStmt::~SelectStmt()
   }
 }
 
-static void wildcard_fields(Table *table, std::vector<FieldDesc> &field_metas)
+static void wildcard_fields(Table *table, std::vector<Field> &field_metas)
 {
   const TableMeta &table_meta = table->table_meta();
   const int field_num = table_meta.field_num();
   for (int i = table_meta.sys_field_num(); i < field_num; i++) {
-    field_metas.push_back(FieldDesc(table, table_meta.field(i)));
+    field_metas.push_back(Field(table, table_meta.field(i)));
   }
 }
 
@@ -64,7 +64,7 @@ RC SelectStmt::create(Db *db, const Selects &select_sql, Stmt *&stmt)
   }
   
   // collect query fields in `select` statement
-  std::vector<FieldDesc> query_fields;
+  std::vector<Field> query_fields;
   for (int i = select_sql.attr_num - 1; i >= 0; i--) {
     const RelAttr &relation_attr = select_sql.attributes[i];
 
@@ -102,7 +102,7 @@ RC SelectStmt::create(Db *db, const Selects &select_sql, Stmt *&stmt)
 	    return RC::SCHEMA_FIELD_MISSING;
 	  }
 
-	  query_fields.push_back(FieldDesc(table, field_meta));
+	  query_fields.push_back(Field(table, field_meta));
 	}
       }
     } else {
@@ -118,7 +118,7 @@ RC SelectStmt::create(Db *db, const Selects &select_sql, Stmt *&stmt)
 	return RC::SCHEMA_FIELD_MISSING;
       }
 
-      query_fields.push_back(FieldDesc(table, field_meta));
+      query_fields.push_back(Field(table, field_meta));
     }
   }
 

src/observer/sql/stmt/select_stmt.h

@@ -18,22 +18,13 @@ See the Mulan PSL v2 for more details. */
 
 #include "rc.h"
 #include "sql/stmt/stmt.h"
+#include "storage/common/field.h"
 
 class FieldMeta;
 class FilterStmt;
 class Db;
 class Table;
 
-// TODO better to create a field class 
-struct FieldDesc
-{
-  Table *table_ = nullptr;
-  const FieldMeta *field_meta_ = nullptr;
-
-  FieldDesc() = default;
-  FieldDesc(Table *table, const FieldMeta *field_meta) : table_(table), field_meta_(field_meta) {}
-};
-
 class SelectStmt : public Stmt
 {
 public:
@@ -47,11 +38,11 @@ public:
 
 public:
   const std::vector<Table *> &tables() const { return tables_; }
-  const std::vector<FieldDesc> &query_fields() const { return query_fields_; }
+  const std::vector<Field> &query_fields() const { return query_fields_; }
   FilterStmt *filter_stmt() const { return filter_stmt_; }
 
 private:
-  std::vector<FieldDesc> query_fields_;
+  std::vector<Field> query_fields_;
   std::vector<Table *> tables_;
   FilterStmt *filter_stmt_ = nullptr;
 };