Refactored the class ResultSet to avoid copying the PGresult,

instead, it will reuse during initialization.

Author: rkhaotix

libs/libconnector/src/connection.cpp

@@ -431,8 +431,7 @@ QStringList Connection::getNotices()
 
 void Connection::executeDMLCommand(const QString &sql, ResultSet &result)
 {
-	ResultSet *new_res=nullptr;
-	PGresult *sql_res=nullptr;
+    PGresult *sql_res = nullptr;
 
 	//Raise an error in case the user try to close a not opened connection
 	if(!connection)
@@ -442,13 +441,11 @@ void Connection::executeDMLCommand(const QString &sql, ResultSet &result)
 	notices.clear();
 
 	//Alocates a new result to receive the resultset returned by the sql command
-	sql_res=PQexec(connection, sql.toStdString().c_str());
+    sql_res = PQexec(connection, sql.toStdString().c_str());
 
 	//Prints the SQL to stdout when the flag is active
 	if(print_sql)
-	{
-		qDebug().noquote() << "\n---\n" << sql;
-	}
+        qDebug().noquote() << "\n---\n" << sql;
 
 	//Raise an error in case the command sql execution is not sucessful
 	if(strlen(PQerrorMessage(connection))>0)
@@ -459,15 +456,8 @@ void Connection::executeDMLCommand(const QString &sql, ResultSet &result)
 						QString(PQresultErrorField(sql_res, PG_DIAG_SQLSTATE)));
 	}
 
-	//Generates the resultset based on the sql result descriptor
-	new_res=new ResultSet(sql_res);
-
-	//Copy the new resultset to the parameter resultset
-	result=*(new_res);
-
-	//Deallocate the new resultset
-	delete new_res;
-	PQclear(sql_res);
+    // Initializes the result set with the PG result instance.
+    result.initResultSet(sql_res);
 }
 
 void Connection::executeDDLCommand(const QString &sql)

libs/libconnector/src/resultset.cpp

@@ -18,68 +18,69 @@
 
 #include "resultset.h"
 #include "exception.h"
+#include <QDebug>
 
 ResultSet::ResultSet()
 {
 	sql_result = nullptr;
 	empty_result = false;
-	is_res_copied = false;
 	current_tuple = -1;
 }
 
-ResultSet::ResultSet(PGresult *sql_result)
+ResultSet::ResultSet(PGresult *sql_result) : ResultSet()
 {
-	QString str_aux;
-	int res_state;
-
-	if(!sql_result)
-		throw Exception(ErrorCode::AsgNotAllocatedSQLResult, __PRETTY_FUNCTION__, __FILE__, __LINE__);
-
-	this->sql_result=sql_result;
-	res_state=PQresultStatus(this->sql_result);
-
-	//Handling the status of the result
-	switch(res_state)
-	{
-		//Generating an error in case the server returns an incomprehensible response
-		case PGRES_BAD_RESPONSE:
-			throw Exception(ErrorCode::IncomprehensibleDBMSResponse, __PRETTY_FUNCTION__, __FILE__, __LINE__);
-
-		//Generating an error in case the server returns a fatal error
-		case PGRES_FATAL_ERROR:
-			str_aux=Exception::getErrorMessage(ErrorCode::DBMSFatalError)
-					.arg(PQresultErrorMessage(sql_result));
-			throw Exception(str_aux,ErrorCode::DBMSFatalError, __PRETTY_FUNCTION__, __FILE__, __LINE__);
-
-		//In case of sucess states the result will be created
-		default:
-			/* For any other result set status different from PGRES_TUPLES_OK
-			 * we flag the result set as empty since they either return no tuples
-			 * or aren't support at the moment by this class */
-			empty_result = res_state != PGRES_TUPLES_OK;
-			current_tuple = -1;
-			is_res_copied = false;
-		break;
-	}
+    initResultSet(sql_result);
 }
 
 ResultSet::~ResultSet()
 {
 	clearResultSet();
 }
 
+void ResultSet::initResultSet(PGresult *sql_res)
+{
+    if(!sql_res)
+        throw Exception(ErrorCode::AsgNotAllocatedSQLResult, __PRETTY_FUNCTION__, __FILE__, __LINE__);
+
+    int res_state = -1;
+
+    clearResultSet();
+    this->sql_result = sql_res;
+    res_state = PQresultStatus(sql_res);
+
+    //Handling the status of the result
+    switch(res_state)
+    {
+        //Generating an error in case the server returns an incomprehensible response
+        case PGRES_BAD_RESPONSE:
+            throw Exception(ErrorCode::IncomprehensibleDBMSResponse, __PRETTY_FUNCTION__, __FILE__, __LINE__);
+
+        //Generating an error in case the server returns a fatal error
+        case PGRES_FATAL_ERROR:
+            throw Exception(Exception::getErrorMessage(ErrorCode::DBMSFatalError)
+                                .arg(PQresultErrorMessage(sql_res)),
+                            ErrorCode::DBMSFatalError, __PRETTY_FUNCTION__, __FILE__, __LINE__);
+
+        //In case of sucess states the result will be created
+        default:
+            /* For any other result set status different from PGRES_TUPLES_OK
+                 * we flag the result set as empty since they either return no tuples
+                 * or aren't support at the moment by this class */
+            empty_result = res_state != PGRES_TUPLES_OK;
+            current_tuple = -1;
+        break;
+    }
+}
+
 void ResultSet::clearResultSet()
 {
-	/* Destroy the resultset of the object if it was not copied
-		to another class instance (see 'operator =') */
-	if(sql_result && !is_res_copied)
-		PQclear(sql_result);
+   if(sql_result)
+      PQclear(sql_result);
 
 	//Reset the other attributes
-	sql_result=nullptr;
-	empty_result=false;
-	is_res_copied=false;
-	current_tuple=-1;
+    sql_result = nullptr;
+    empty_result = false;
+    current_tuple = -1;
 }
 
 QString ResultSet::getColumnName(int column_idx)
@@ -89,7 +90,10 @@ QString ResultSet::getColumnName(int column_idx)
 		throw Exception(ErrorCode::RefTupleColumnInvalidIndex, __PRETTY_FUNCTION__, __FILE__, __LINE__);
 
 	//Returns the column name on the specified index
-	return QString(PQfname(sql_result, column_idx));
+    //QString col_name { PQfname(sql_result, column_idx) };
+    //return col_name;
+
+    return { PQfname(sql_result, column_idx) };
 }
 
 QStringList ResultSet::getColumnNames()
@@ -332,20 +336,3 @@ bool ResultSet::isValid()
 	return (sql_result != nullptr);
 }
 
-void ResultSet::operator = (ResultSet &res)
-{
-	/* Mark the result parameter as copied, avoiding
-		the sql_result attribute to be deallocated */
-	res.is_res_copied=true;
-
-	/* If the resultset 'this' is allocated,
-		it will be deallocated to avoid memory leaks */
-	clearResultSet();
-
-	//Copy the parameter restulset attributes to 'this' resultset
-	this->current_tuple=res.current_tuple;
-	this->empty_result=res.empty_result;
-	this->sql_result=PQcopyResult(res.sql_result, PG_COPYRES_TUPLES | PG_COPYRES_ATTRS | PG_COPYRES_EVENTS);
-	this->is_res_copied=false;
-}
-

libs/libconnector/src/resultset.h

@@ -38,19 +38,15 @@ It the resultset contains data the user must call ResultSet::accessTuple() to ac
 
 class __libconnector ResultSet {
 	private:
-		/*! \brief Indicates whether the result was copied, this flag is used
-	 to avoid segmentation faults when calling the destructor.
-	 As the pointer 'sql_result' is copied
-	 to other elements if it is destroyed can cause
-	 reference fails. Thus, such a pointer is only deleted
-	 when this flag is marked as false */
-		bool is_res_copied;
-
 		void validateColumnIndex(int column_idx);
 
 		int validateColumnName(const QString &column_name);
 
-	protected:
+        void initResultSet(PGresult *sql_res);
+
+        void clearResultSet();
+
+    protected:
 		//! \brief Stores the current tuple index, just for navigation
 		int current_tuple;
 
@@ -61,8 +57,12 @@ class __libconnector ResultSet {
 		//! \brief Stores the result object of a SQL command
 		PGresult *sql_result;
 
-		/*! \brief This class may be constructed from a
-	 result of SQL command generated in DBConnection class */
+        /*! \brief This class may be constructed from a
+         * result of SQL command generated in Connection class.
+         * The ResultSet takes the ownership of the provided sql_result,
+         * so there's no need to call PQclear() over it after instantiate
+         * an object of this class. When destroyed, the instance will
+         * free the PGresult. (see clearResultSet) */
 		ResultSet(PGresult *sql_result);
 
 	public:
@@ -75,6 +75,9 @@ class __libconnector ResultSet {
 		};
 
 		ResultSet();
+
+         /*! \brief Destroys the result set using clearResultSet.
+          * The internal PostgreSQL result set (sql_result) is automatically freed */
 		~ResultSet();
 
 		//! \brief Returns the value of a column (searching by name or index)
@@ -88,9 +91,9 @@ class __libconnector ResultSet {
 		//! \brief Returns all the column names / values for the current tuple.
 		attribs_map getTupleValues();
 
-		/*! \brief Returns the number of rows affected by the command that generated
-	 the result if it is an INSERT, DELETE, UPDATE or the number of
-	 tuples returned if the command was a SELECT */
+        /*! \brief Returns the number of rows affected by the command that generated
+         * the result if it is an INSERT, DELETE, UPDATE or the number of
+         * tuples returned if the command was a SELECT */
 		int getTupleCount();
 
 		//! \brief Returns the column count present in one tuple
@@ -128,10 +131,8 @@ class __libconnector ResultSet {
 		//! \brief Returns if the result set is valid (created from a valid result set)
 		bool isValid();
 
-		void clearResultSet();
-
-		//! \brief Make a copy between two resultsets
-		void operator = (ResultSet &res);
+        ResultSet &operator = (const PGresult *) = delete;
+        ResultSet &operator = (const ResultSet &) = delete;
 
 		friend class Connection;
 };

pgmodeler.pri

@@ -271,7 +271,7 @@ windows {
   !defined(PGSQL_LIB, var): PGSQL_LIB = C:/msys64/mingw64/bin/libpq.dll
   !defined(PGSQL_INC, var): PGSQL_INC = C:/msys64/mingw64/include
   !defined(XML_INC, var): XML_INC = C:/msys64/mingw64/include/libxml2
-  !defined(XML_LIB, var): XML_LIB = C:/msys64/mingw64/bin/libxml2-2.dll
+  !defined(XML_LIB, var): XML_LIB = C:/msys64/mingw64/bin/libxml2-16.dll
   INCLUDEPATH += "$$PGSQL_INC" "$$XML_INC"
 }