Index: openacs-4/packages/acs-content-repository/sql/postgresql/upgrade/upgrade-5.10.0d10-5.10.0d11.sql
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-content-repository/sql/postgresql/upgrade/Attic/upgrade-5.10.0d10-5.10.0d11.sql,v
diff -u -N
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ openacs-4/packages/acs-content-repository/sql/postgresql/upgrade/upgrade-5.10.0d10-5.10.0d11.sql	14 Mar 2020 17:17:16 -0000	1.1.2.1
@@ -0,0 +1,61 @@
+--
+-- Use stable and strict SQL functions for
+--
+--   * content_folder__is_folder
+--   * content_folder__is_sub_folder, and
+--   * content_folder__is_empty
+--
+-- with simpler boolean result.
+--
+
+--
+-- procedure content_folder__is_folder/1
+--
+select define_function_args('content_folder__is_folder','item_id');
+
+CREATE OR REPLACE FUNCTION content_folder__is_folder(
+   item_id integer
+) RETURNS boolean AS $$
+
+  SELECT EXISTS (
+    SELECT 1 from cr_folders where folder_id = item_id
+  );
+
+$$ LANGUAGE sql stable strict;
+
+--
+-- procedure content_folder__is_sub_folder/2
+--
+select define_function_args('content_folder__is_sub_folder','folder_id,target_folder_id');
+
+CREATE OR REPLACE FUNCTION content_folder__is_sub_folder(
+   is_sub_folder__folder_id integer,
+   is_sub_folder__target_folder_id integer
+) RETURNS boolean AS $$
+
+  WITH RECURSIVE parents AS (
+       select item_id, parent_id from cr_items where item_id = is_sub_folder__target_folder_id
+    UNION ALL
+       select cr_items.item_id, cr_items.parent_id from cr_items, parents
+       where cr_items.item_id = parents.parent_id
+  )
+  SELECT EXISTS (
+    SELECT 1 FROM parents WHERE parent_id = is_sub_folder__folder_id
+  );
+$$ LANGUAGE sql stable strict;
+
+
+--
+-- procedure content_folder__is_empty/1
+--
+select define_function_args('content_folder__is_empty','folder_id');
+
+CREATE OR REPLACE FUNCTION content_folder__is_empty(
+   is_empty__folder_id integer
+) RETURNS boolean AS $$
+
+  SELECT NOT EXISTS (
+    SELECT 1 from cr_items where parent_id = is_empty__folder_id
+  );
+
+$$ LANGUAGE sql stable strict;