[Qt] Add dbcache migration path

Github-Pull: #8407
Rebased-From: 893f379ba0

src/qt/optionsmodel.cpp

@@ -43,6 +43,8 @@ void OptionsModel::Init(bool resetSettings)
     if (resetSettings)
         Reset();
 
+    checkAndMigrate();
+
     QSettings settings;
 
     // Ensure restart flag is unset on client startup
@@ -429,3 +431,22 @@ bool OptionsModel::isRestartRequired()
     QSettings settings;
     return settings.value("fRestartRequired", false).toBool();
 }
+
+void OptionsModel::checkAndMigrate()
+{
+    // Migration of default values
+    // Check if the QSettings container was already loaded with this client version
+    QSettings settings;
+    static const char strSettingsVersionKey[] = "nSettingsVersion";
+    int settingsVersion = settings.contains(strSettingsVersionKey) ? settings.value(strSettingsVersionKey).toInt() : 0;
+    if (settingsVersion < CLIENT_VERSION)
+    {
+        // -dbcache was bumped from 100 to 300 in 0.13
+        // see https://github.com/bitcoin/bitcoin/pull/8273
+        // force people to upgrade to the new value if they are using 100MB
+        if (settingsVersion < 130000 && settings.contains("nDatabaseCache") && settings.value("nDatabaseCache").toLongLong() == 100)
+            settings.setValue("nDatabaseCache", (qint64)nDefaultDbCache);
+
+        settings.setValue(strSettingsVersionKey, CLIENT_VERSION);
+    }
+}

src/qt/optionsmodel.h

@@ -84,9 +84,11 @@ private:
     /* settings that were overriden by command-line */
     QString strOverriddenByCommandLine;
 
-    /// Add option to list of GUI options overridden through command line/config file
+    // Add option to list of GUI options overridden through command line/config file
     void addOverriddenOption(const std::string &option);
 
+    // Check settings version and upgrade default values if required
+    void checkAndMigrate();
 Q_SIGNALS:
     void displayUnitChanged(int unit);
     void coinControlFeaturesChanged(bool);