Fix connection access issue.

Author: guzman-raphael

datajoint/connection.py

@@ -235,7 +235,6 @@ def purge_query_cache(self):
             path_iter = pathlib.Path(config['query_cache']).glob('**/*')
             for path in path_iter:
                 path.unlink()
-        self._query_cache = None
 
     def close(self):
         self._conn.close()

docs-parts/queries/12-Query-Caching_lang1.rst

@@ -4,12 +4,10 @@
   # set the query cache path
   dj.config['query_cache'] = os.path.expanduser('~/dj_query_cache')
 
-  # access the currently active connection object
-  conn = dj.conn()
-  ## OR
-  conn = schema.connection
-  ## OR
-  conn = table.connection
+  # access the active connection object for the tables
+  conn = dj.conn() # if queries co-located with tables
+  conn = module.schema.connection # if schema co-located with tables
+  conn = module.table.connection # most flexible
 
   # activate query caching for a namespace called 'main'
   conn.set_query_cache(query_cache='main')

tests/test_fetch.py

@@ -261,28 +261,29 @@ def test_query_caching(self):
         os.mkdir(os.path.expanduser('~/dj_query_cache'))
 
         with dj.config(query_cache=os.path.expanduser('~/dj_query_cache')):
+            conn = schema.TTest3.connection
             # insert sample data and load cache
             schema.TTest3.insert([dict(key=100+i, value=200+i) for i in range(2)])
-            dj.conn().set_query_cache(query_cache='main')
+            conn.set_query_cache(query_cache='main')
             cached_res = schema.TTest3().fetch()
             # attempt to insert while caching enabled
             try:
                 schema.TTest3.insert([dict(key=200+i, value=400+i) for i in range(2)])
-                assert False, 'Insert allowed which query caching enabled'
+                assert False, 'Insert allowed while query caching enabled'
             except dj.DataJointError:
-                dj.conn().set_query_cache()
+                conn.set_query_cache()
             # insert new data
             schema.TTest3.insert([dict(key=600+i, value=800+i) for i in range(2)])
             # re-enable cache to access old results
-            dj.conn().set_query_cache(query_cache='main')
+            conn.set_query_cache(query_cache='main')
             previous_cache = schema.TTest3().fetch()
             # verify properly cached and how to refresh results
             assert all([c == p for c, p in zip(cached_res, previous_cache)])
-            dj.conn().set_query_cache()
+            conn.set_query_cache()
             uncached_res = schema.TTest3().fetch()
             assert len(uncached_res) > len(cached_res)
             # purge query cache
-            dj.conn().purge_query_cache()
+            conn.purge_query_cache()
 
         # reset cache directory state (will fail if purge was unsuccessful)
         os.rmdir(os.path.expanduser('~/dj_query_cache'))