From: APTX <marek321@gmail.com>
Date: Wed, 5 Jun 2013 12:32:50 +0000 (+0200)
Subject: Add support for nested database transactions.
X-Git-Url: https://gitweb.tyo.aptx.org/?a=commitdiff_plain;h=f5922f9e41bcfd7d8a917a5eba9de5e5078ff362;p=localmylist.git

Add support for nested database transactions.
---

diff --git a/localmylist/database.cpp b/localmylist/database.cpp
index c98070f..20c16e1 100644
--- a/localmylist/database.cpp
+++ b/localmylist/database.cpp
@@ -9,15 +9,41 @@
 #include <QThread>
 #include <QDebug>
 
+#include <functional>
+
 namespace LocalMyList {
 
 struct DatabaseInternal
 {
+	DatabaseInternal() : transactionLevel(0) {}
+
 	QSqlDatabase db;
 
 	QHash<const char *const, QSqlQuery> preparedQueries;
+	int transactionLevel;
 
 	QThread *thread;
+
+	bool transactionInternal(std::function<bool()> transaction, std::function<bool()> savepoint)
+	{
+		if (transactionLevel)
+		{
+			if (!savepoint())
+			{
+				qDebug() << "Savepoint Transaction Error:" << db.lastError();
+				return false;
+			}
+		}
+		else
+		{
+			if (!transaction())
+			{
+				qDebug() << "Transaction Error:" << db.lastError();
+				return false;
+			}
+		}
+		return true;
+	}
 };
 
 Database::Database(const QString &connectionName) : d(0)
@@ -56,33 +82,56 @@ bool Database::transaction()
 {
 	Q_ASSERT_X(d->thread == QThread::currentThread(), "threads", "DB used from different thread");
 
-	bool success = d->db.transaction();
-	if (success)
-		return true;
-	qDebug() << "Transaction Error:" << d->db.lastError();
-	return false;
+
+	if (!d->transactionInternal(
+			[this]{ return d->db.transaction(); },
+			[this]{ return exec("SAVEPOINT transaction_level_" + QString::number(d->transactionLevel)); }))
+	{
+		return false;
+	}
+
+	++d->transactionLevel;
+	return true;
 }
 
 bool Database::commit()
 {
 	Q_ASSERT_X(d->thread == QThread::currentThread(), "threads", "DB used from different thread");
 
-	bool success = d->db.commit();
-	if (success)
-		return true;
-	qDebug() << "Commit Error:" << d->db.lastError();
-	return false;
+	if (!d->transactionLevel)
+		return false;
+
+	--d->transactionLevel;
+
+	if (!d->transactionInternal(
+			[this]{ return d->db.commit(); },
+			[this]{ return exec("RELEASE SAVEPOINT transaction_level_" + QString::number(d->transactionLevel)); }))
+	{
+		d->transactionLevel = 0;
+		return false;
+	}
+
+	return true;
 }
 
 bool Database::rollback()
 {
 	Q_ASSERT_X(d->thread == QThread::currentThread(), "threads", "DB used from different thread");
 
-	bool success = d->db.rollback();
-	if (success)
-		return true;
-qDebug() << "Commit Error:" << d->db.lastError();
-return false;
+	if (!d->transactionLevel)
+		return false;
+
+	--d->transactionLevel;
+
+	if (!d->transactionInternal(
+			[this]{ return d->db.rollback(); },
+			[this]{ return exec("ROLLBACK TO SAVEPOINT transaction_level_" + QString::number(d->transactionLevel)); }))
+	{
+		d->transactionLevel = 0;
+		return false;
+	}
+
+	return true;
 }
 
 OpenFileData Database::firstUnwatchedByExactTitle(const QString &title)
@@ -1584,6 +1633,7 @@ void Database::disconnect()
 		return;
 
 	d->preparedQueries.clear();
+	d->transactionLevel = 0;
 
 	auto subscribedNotifications = d->db.driver()->subscribedToNotifications();
 	foreach (const QString &notification, subscribedNotifications)