Got the SqlAlchemy query to work

app/dao/templates_dao.py

@@ -1,6 +1,7 @@
 import uuid
 
-from sqlalchemy import (desc, text)
+import sqlalchemy
+from sqlalchemy import desc
 
 from app import db
 from app.models import (Template, TemplateHistory)
@@ -61,11 +62,21 @@ def dao_get_template_versions(service_id, template_id):
 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()
+    # 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),
+                                                             uuid.UUID(template_id.decode())).label('template_id'),
+                         sqlalchemy.sql.expression.bindparam("count" + str(i), int(count.decode())).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,
+                                    Template.id == cache_subq.c.template_id
+                                    ).order_by(Template.name)
+
+    return query.all()