Rails 3 - Awesome Nested Set - Comment.rebuild! - Results in a ERROR - ruby-on-rails

Question

I'm using the awesome_nested_set rails 3 fork here: https://github.com/FreakyDazio/awesome_nested_set
I'm trying to rebuild the nesting per the installation instructions.
I went to console and typed in:
>>Comment.rebuild!
But that errors with:
ActiveRecord::StatementInvalid: PGError: ERROR: column "comments.created_at" must appear in the GROUP BY clause or be used in an aggregate function
LINE 2: HAVING COUNT("lft") > 1 ORDER BY comments.cr...
^
: SELECT "lft", COUNT("lft") FROM "comments" GROUP BY "lft"
HAVING COUNT("lft") > 1 ORDER BY comments.created_at DESC LIMIT 1
Any thoughts or ideas why?
Thanks

Answer 1

This same issues is reported in another fork of acts_as_nested_set (you seem to have all the bad luck. :) See this error report. He does mention a workaround you can put in your model:
def self.all_roots_valid?
if acts_as_nested_set_options[:scope]
roots.group_by{|record| scope_column_names.collect{|col| record.send(col.to_sym)}}.all? do |scope, grouped_roots|
each_root_valid?(grouped_roots)
end
else
each_root_valid?(roots)
end
end