How to do ALTER EXTENSION with Heroku's Postgres DB? - ruby-on-rails

Question

I'm using the apartment gem for my SaaS (built with Ruby on Rails) and one of its requirements is we need to install the hstore PostgreSQL extension via a dedicated schema (ie: shared_extensions), not the default public schema.
Heroku enables hstore by default; however it is installed in the public schema. When I tried to do:
ActiveRecord::Base.connection.execute("ALTER EXTENSION hstore SET SCHEMA hstore;")
the console returned:
(3.6ms) ALTER EXTENSION hstore SET SCHEMA hstore;
PG::Error: ERROR: must be owner of extension hstore
Currently it's impossible on the code side to make do with hstore extension being installed on public, so I definitely have to find a way to put hstore extension on shared_extensions schema.
Will there be a way to do this on Heroku? Thanks.

Answer 1

A less destructive alternative work around:
1.) Put your application in maintenance mode:
heroku maintenance:on -a [app-name]
2.) Backup up your database: ALWAYS BACK IT UP :)
heroku pg:backups capture -a [app-name]
3.) Copy your database locally:
heroku pg:pull [Database URL] mylocaldb -a [app-name]
4.) Now you have the db locally, you can move the extensions without any destruction of data or columns because you have local superuser priv.:
ALTER EXTENSION "hstore" SET SCHEMA hstore;
5.) Now export this version back to production:
heroku pg:push mylocaldb [Database URL] -a [app-name]
6.) Take your app out of maint. mode and you now have the extensions installed in the shared schema of hstore.
7.) You will still need to perform step 1 of Tu H.'s response if you are on rails < 4.1
OR if you are running rails 4.1+ you can just update your database.yml file:
schema_search_path: "public,hstore"
This is a less destructive way to get what you want done without too much downtime.

Answer 2

Turns out I can't do ALTER EXTENSION hstore SET SCHEMA hstore; on Heroku. I've documented the workaround here
Append ?schema_search_path=public,hstore to your DATABASE_URL environment variable, by this you don't have to revise the database.yml file (which is impossible since Heroku regenerates a completely different and immutable database.yml of its own on each deploy)
Run heroku pg:psql from your command line
And then DROP EXTENSION hstore; (Note: This will drop all columns that use hstore type, so proceed with caution; only do this with a fresh PostgreSQL instance)
Next: CREATE SCHEMA IF NOT EXISTS hstore;
Finally: CREATE EXTENSION IF NOT EXISTS hstore SCHEMA hstore; and hit enter (\q to exit)