diff --git a/database.cpp b/database.cpp
index 5006db4..7976fea 100644
--- a/database.cpp
+++ b/database.cpp
@@ -15,7 +15,7 @@ bool Database::init()
     QString path = QStandardPaths::writableLocation(QStandardPaths::AppDataLocation);
     QDir dir(path);
 
-    m_database = QSqlDatabase::addDatabase("QSQLITE");
+    QSqlDatabase m_database = QSqlDatabase::addDatabase("QSQLITE");
 
     if(!dir.mkpath("."))
         return false;
@@ -30,6 +30,7 @@ bool Database::init()
             m_database.exec("CREATE TABLE IF NOT EXISTS fits_files (id INTEGER PRIMARY KEY AUTOINCREMENT, file VARCHAR(255) UNIQUE, mtime DATETIME)");
             m_database.exec("CREATE TABLE IF NOT EXISTS fits_headers (id INTEGER PRIMARY KEY AUTOINCREMENT, id_file INTEGER,"
                             "key VARCHAR(81), value VARCHAR(81), comment VARCHAR(81), FOREIGN KEY(id_file) REFERENCES fits_files(id) ON DELETE CASCADE)");
+            m_database.exec("CREATE INDEX IF NOT EXISTS key_value    ON fits_headers(key, value)");
             QSqlError error = m_database.lastError();
 
             if(error.type() == QSqlError::NoError)
@@ -64,27 +65,27 @@ bool Database::mark(const QString &filename)
 {
     m_markQuery.bindValue(0, filename);
     m_markQuery.exec();
-    return checkError();
+    return checkError(m_markQuery);
 }
 
 bool Database::unmark(const QString &filename)
 {
     m_unmarkQuery.bindValue(0, filename);
     m_unmarkQuery.exec();
-    return checkError();
+    return checkError(m_unmarkQuery);
 }
 
 bool Database::isMarked(const QString &filename)
 {
     m_isMarkedQuery.bindValue(":name", filename);
     m_isMarkedQuery.exec();
-    checkError();
+    checkError(m_isMarkedQuery);
     return m_isMarkedQuery.next();
 }
 
 QStringList Database::getMarkedFiles()
 {
-    QSqlQuery markedFiles("SELECT * from files", m_database);
+    QSqlQuery markedFiles("SELECT * from files");
 
     QStringList files;
     while(markedFiles.next())
@@ -96,9 +97,9 @@ QStringList Database::getMarkedFiles()
     return files;
 }
 
-bool Database::checkError()
+bool Database::checkError(QSqlQuery &query)
 {
-    QSqlError error = m_database.lastError();
+    QSqlError error = query.lastError();
     if(error.type() == QSqlError::NoError)
         return true;
     else
@@ -124,11 +125,12 @@ void Database::indexDir(const QDir &dir, QProgressDialog *progress)
     m_progress = 0;
     int count = countFiles(dir);
     progress->setMaximum(count);
-    m_database.transaction();
+    QSqlDatabase database = QSqlDatabase::database();
+    database.transaction();
     if(indexDir2(dir, progress))
-        m_database.commit();
+        database.commit();
     else
-        m_database.rollback();
+        database.rollback();
 }
 
 QStringList Database::getFitsKeywords()
diff --git a/database.h b/database.h
index f2500ca..888d216 100644
--- a/database.h
+++ b/database.h
@@ -10,7 +10,6 @@
 class Database : public QObject
 {
     Q_OBJECT
-    QSqlDatabase m_database;
     QSqlQuery m_markQuery;
     QSqlQuery m_unmarkQuery;
     QSqlQuery m_isMarkedQuery;
@@ -34,7 +33,7 @@ public:
     QStringList getFitsKeywords();
 protected:
     bool indexDir2(const QDir &dir, QProgressDialog *progress);
-    bool checkError();
+    bool checkError(QSqlQuery &query);
 };
 
 #endif // DATABASE_H