Thanks for your reply Tom. I've found that the culprit is the function parentContainers(), which recurses in a folder structure and looks like this:
create function parentContainers(numeric) returns setof numeric
as '
select parentContainers( (select container_id from container where id = $1 ) )
union
select id from container where id = $1
' language sql stable returns null on null input;
Is is declared stable, but I know that is just planner hint, so it doesn't guarantee that it will only get called once. If I replace the function call with the two values this function returns,
