Added a redis cache for the template usage stats.

Cache expires every 10 minutes, but will help with the every 2 second query, especially when a job is running.
There is some clean up and qa to do for this yet

app/dao/templates_dao.py

@@ -1,6 +1,7 @@
 import uuid
 
-from sqlalchemy import (asc, desc)
+import sqlalchemy
+from sqlalchemy import (desc, cast, String, text)
 
 from app import db
 from app.models import (Template, TemplateHistory)
@@ -56,3 +57,39 @@ def dao_get_template_versions(service_id, template_id):
     ).order_by(
         desc(TemplateHistory.version)
     ).all()
+
+
+# def dao_get_templates_by_for_cache(cache):
+#     if not cache or len(cache) == 0:
+#         return []
+
+#     # First create a subquery that is a union select of the cache values
+#     # Then join templates to the subquery
+#     cache_queries = [
+#         db.session.query(sqlalchemy.sql.expression.bindparam("template_id" + str(i),
+#                                                               template_id).label('template_id'),
+#                          sqlalchemy.sql.expression.bindparam("count" + str(i), count).label('count'))
+#         for i, (template_id, count) in enumerate(cache)]
+#     cache_subq = cache_queries[0].union(*cache_queries[1:]).subquery()
+#     query = db.session.query(Template.id.label('template_id'),
+#                              Template.template_type,
+#                              Template.name,
+#                              cache_subq.c.count.label('count')
+#                              ).join(cache_subq,
+#                                     cast(Template.id, String) == cast(cache_subq.c.template_id, String)
+#                                     ).order_by(Template.name)
+#
+#     return query.all()
+
+
+def dao_get_templates_by_for_cache(cache):
+    if not cache or len(cache) == 0:
+        return []
+    txt = "( " + " Union all ".join(
+        "select '{}'::text as template_id, {} as count".format(x.decode(),
+                                                               y.decode()) for x, y in cache) + " ) as cache"
+    txt = "Select t.id as template_id, t.template_type, t.name, cache.count from templates t,  " + \
+          txt + " where t.id::text = cache.template_id order by t.name"
+    stmt = text(txt)
+
+    return db.session.execute(stmt).fetchall()