Add postgresql function for access to pickle tags array and aggregate it.

sql/tags.sql

@@ -0,0 +1,24 @@
+CREATE OR REPLACE FUNCTION unpickle (data text)
+  RETURNS text[]
+AS $$
+    import base64
+    import pickle
+
+    return pickle.loads(base64.b64decode(data))
+$$ LANGUAGE plpythonu;
+
+CREATE OR REPLACE FUNCTION array_uniq_join (data text[], data2 text[])
+  RETURNS text[]
+AS $$
+    tmp = set(data)
+    tmp.update(data2)
+    return tuple(tmp)
+$$ LANGUAGE plpythonu;
+
+DROP AGGREGATE array_uniq_concat (text[]);
+CREATE AGGREGATE array_uniq_concat (text[])
+(
+    sfunc = array_uniq_join,
+    stype = text[],
+    initcond = '{}'
+);