Why do I get Postgres extension errors when I run `rake db:structure:load` or `rake db:setup`?
When Rails generates
structure.sql, it includes commands to enable the database extensions it wants to use. Unfortunately, these are blocked by
heroku-postgresql. One way around this is to use
config.active_record.schema_format = :ruby, which means your app would generate a
schema.rb instead of a
schema.rbis compatible with
heroku-postgresql because it doesn't enable extensions.
If you need to use
structure.sql you can remove
COMMENT ON EXTENSION plpgsql IS 'PL/pgSQL procedural language'; which should also resolve this issue.