2 files changed, 20 insertions, 6 deletions
diff --git a/vk/tracking/db/format.py b/vk/tracking/db/format.py
index 7b3f312..f9a670c 100644
--- a/vk/tracking/db/format.py
+++ b/vk/tracking/db/format.py
@@ -27,13 +27,23 @@ class Format(Enum):
             raise NotImplementedError('unsupported database format: ' + str(self))
 
     def open_output_file(self, path=None):
-        if self is Format.CSV or self is Format.LOG:
-            return io.open_output_text_file(path)
+        if self is Format.CSV:
+            return self._open_output_database_file(path)
+        elif self is Format.LOG:
+            return self._open_output_log_file(path)
         elif self is Format.NULL:
-            return io.open_output_text_file(None)
+            return self._open_output_database_file(None)
         else:
             raise NotImplementedError('unsupported database format: ' + str(self))
 
+    @staticmethod
+    def _open_output_log_file(path):
+        return io.open_output_text_file(path, mode='a')
+
+    @staticmethod
+    def _open_output_database_file(path):
+        return io.open_output_text_file(path, mode='x')
+
     def create_reader(self, fd=sys.stdin):
         if self is Format.CSV:
             return backend.csv.Reader(fd)
diff --git a/vk/tracking/db/io.py b/vk/tracking/db/io.py
index 805334d..d280634 100644
--- a/vk/tracking/db/io.py
+++ b/vk/tracking/db/io.py
@@ -36,8 +36,12 @@ def _open_file(path=None, default=None, **kwargs):
         if fd is not default:
             fd.close()
 
-def open_output_text_file(path=None):
-    return _open_file(path, default=sys.stdout, mode='w', encoding='utf-8')
+_DEFAULT_ENCODING = 'utf-8'
+
+def open_output_text_file(path=None, mode='w'):
+    return _open_file(path, default=sys.stdout, mode=mode,
+                      encoding=_DEFAULT_ENCODING)
 
 def open_input_text_file(path=None):
-    return _open_file(path, default=sys.stdin, mode='r', encoding='utf-8')
+    return _open_file(path, default=sys.stdin, mode='r',
+                      encoding=_DEFAULT_ENCODING)