From e7da254c5e7c0fc07a811abfd3fcf030c46d643b Mon Sep 17 00:00:00 2001
From: "Wladimir J. van der Laan" <laanwj@gmail.com>
Date: Thu, 28 Jul 2016 11:10:14 +0200
Subject: [PATCH] Merge #8407: [Qt] Add dbcache migration path

893f379 [Qt] Add dbcache migration path (Jonas Schnelli)
---
 src/qt/optionsmodel.cpp | 21 +++++++++++++++++++++
 src/qt/optionsmodel.h   |  4 +++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/qt/optionsmodel.cpp b/src/qt/optionsmodel.cpp
index 6d03b4f9f..df887eba4 100644
--- a/src/qt/optionsmodel.cpp
+++ b/src/qt/optionsmodel.cpp
@@ -48,6 +48,8 @@ void OptionsModel::Init(bool resetSettings)
     if (resetSettings)
         Reset();
 
+    checkAndMigrate();
+
     this->resetSettings = resetSettings;
 
     QSettings settings;
@@ -552,3 +554,22 @@ 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);
+    }
+}
\ No newline at end of file
diff --git a/src/qt/optionsmodel.h b/src/qt/optionsmodel.h
index 88839639d..cbe90a799 100644
--- a/src/qt/optionsmodel.h
+++ b/src/qt/optionsmodel.h
@@ -95,9 +95,11 @@ 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 privateSendRoundsChanged();