Flush caches before updating index

This is mostly needed for testsuite, but might be triggered in some
complex setups as well.

trans/management/commands/rebuild_index.py

@@ -21,7 +21,8 @@
 from trans.management.commands import WeblateCommand
 from lang.models import Language
 from trans.search import (
-    update_index, create_source_index, create_target_index
+    update_index, create_source_index, create_target_index,
+    flush_caches
 )
 from optparse import make_option
 
@@ -47,4 +48,6 @@ class Command(WeblateCommand):
 
         units = self.get_units(*args, **options)
 
+        flush_caches()
+
         update_index(units)

trans/search.py

@@ -112,6 +112,13 @@ def update_index(units, source_units=None):
                 )
 
 
+def flush_caches():
+    '''
+    Flushes internal caches.
+    '''
+    FULLTEXT_INDEX.flush_caches()
+
+
 class Index(object):
     '''
     Class to manage index readers and writers.
@@ -177,5 +184,11 @@ class Index(object):
         '''
         return self.target(lang).searcher()
 
+    def flush_caches():
+        '''
+        Flushes internal caches.
+        '''
+        self._source = None
+        self._target = {}
 
 FULLTEXT_INDEX = Index()