Always reset prepared sql statements

This allow the creation of checkpoints and fixes the growing wal issue

Fixes: #7646

changelog/unreleased/7646

@@ -0,0 +1,5 @@
+Bugfix: SQLite wal file grows to several gigabyte
+
+We fixed a bug where the SQLite wal file growed until the client was quit.
+
+https://github.com/owncloud/client/issues/7646

src/common/ownsql.cpp

@@ -494,18 +494,28 @@ void SqlQuery::reset_and_clear_bindings()
     }
 }
 
-bool SqlQuery::initOrReset(const QByteArray &sql, OCC::SqlDatabase &db)
+PreparedSqlQueryRAII::PreparedSqlQueryRAII(SqlQuery *query)
+    : _query(query)
 {
-    OC_ENFORCE(!_sqldb || &db == _sqldb);
-    _sqldb = &db;
-    _db = db.sqliteDb();
-    if (_stmt) {
-        reset_and_clear_bindings();
-        return true;
-    } else {
-        return prepare(sql) == 0;
+    Q_ASSERT(!sqlite3_stmt_busy(_query->_stmt));
+}
+
+PreparedSqlQueryRAII::PreparedSqlQueryRAII(SqlQuery *query, const QByteArray &sql, SqlDatabase &db)
+    : _query(query)
+{
+    Q_ASSERT(!sqlite3_stmt_busy(_query->_stmt));
+    OC_ENFORCE(!query->_sqldb || &db == query->_sqldb);
+    query->_sqldb = &db;
+    query->_db = db.sqliteDb();
+    if (!query->_stmt) {
+        _ok = query->prepare(sql) == 0;
     }
 }
 
+PreparedSqlQueryRAII::~PreparedSqlQueryRAII()
+{
+    _query->reset_and_clear_bindings();
+}
+
 
 } // namespace OCC

src/common/ownsql.h

@@ -104,12 +104,6 @@ class OCSYNC_EXPORT SqlQuery
     explicit SqlQuery() = default;
     explicit SqlQuery(SqlDatabase &db);
     explicit SqlQuery(const QByteArray &sql, SqlDatabase &db);
-    /**
-     * Prepare the SqlQuery if it was not prepared yet.
-     * Otherwise, clear the results and the bindings.
-     * return false if there is an error
-     */
-    bool initOrReset(const QByteArray &sql, SqlDatabase &db);
     /**
      * Prepare the SqlQuery.
      * If the query was already prepared, this will first call finish(), and re-prepare it.
@@ -167,8 +161,43 @@ class OCSYNC_EXPORT SqlQuery
     QString _error;
     int _errId;
     QByteArray _sql;
+
+    friend class PreparedSqlQueryRAII;
 };
 
+class OCSYNC_EXPORT PreparedSqlQueryRAII
+{
+public:
+    /**
+     * Simple Guard which allow reuse of prepared querys.
+     * The queries are reset in the destructor to prevent wal locks
+     */
+    PreparedSqlQueryRAII(SqlQuery *query);
+    /**
+     * Prepare the SqlQuery if it was not prepared yet.
+     */
+    PreparedSqlQueryRAII(SqlQuery *query, const QByteArray &sql, SqlDatabase &db);
+    ~PreparedSqlQueryRAII();
+
+    explicit operator bool() const { return _ok; }
+
+    SqlQuery *operator->() const
+    {
+        Q_ASSERT(_ok);
+        return _query;
+    }
+
+    SqlQuery &operator*() const &
+    {
+        Q_ASSERT(_ok);
+        return *_query;
+    }
+
+private:
+    SqlQuery *const _query;
+    bool _ok = true;
+    Q_DISABLE_COPY(PreparedSqlQueryRAII);
+};
 } // namespace OCC
 
 #endif // OWNSQL_H