Datastore problem with ckan2.7

[roll]

Overview

With this line in Dockerfile we solve the psycopg2 bug related to postgresql-client@10:

    # Workaround to solve https://github.com/psycopg/psycopg2/issues/594 in Alpine 3.7
	sed -i -e "s/psycopg2==2.4.5/psycopg2==2.7.3.2/g" requirements.txt && \

But at the same time it seems there are breaking changes between these versions of psycopg. For example a query like this:

http://ckan-dev:5000/api/3/action/datastore_search_sql?sql=SELECT%20DISTINCT%20%22Sex%22%20FROM%20%22723c1bca-c4da-4a84-b99b-7140e242921f%22

will fail because of the fact that the latter psycopg returns already parsed dict instead of JSON:

ckan/ckanext/datastore/helpers.py

        query_plan = json.loads(result['QUERY PLAN'])
        plan = query_plan[0]['Plan']

I was able to solve it patching CKAN:

diff --git a/ckanext/datastore/helpers.py b/ckanext/datastore/helpers.py
index b616f0f94..ec1428d1d 100644
--- a/ckanext/datastore/helpers.py
+++ b/ckanext/datastore/helpers.py
@@ -105,8 +105,8 @@ def get_table_names_from_sql(context, sql):
     table_names = []

     try:
-        query_plan = json.loads(result['QUERY PLAN'])
-        plan = query_plan[0]['Plan']
+        # TODO: add comment and issue
+        plan = result['QUERY PLAN'][0]['Plan']

         table_names.extend(_get_table_names_from_plan(plan))

But it's only for this exact problem - not sure are there other breaking changes in psycopg2