Rails 3.1 - Pushing to Heroku - Errors installing postgres adapter? - postgresql

Question

I just upgraded to Rails 3.1 and the first app i've tried to deploy to Heroku has encountered a problem relating to Postgres adapter. I'm able to push the app to heroku but then when i try to migrate the database i get the following error:
heroku rake db:migrate
rake aborted!
Please install the postgresql adapter: `gem install activerecord-postgresql-adapter`
(pg is not part of the bundle. Add it to Gemfile.)
Tasks: TOP => db:migrate => db:load_config
(See full trace by running task with --trace)
when I try their suggested install i get:
ERROR: Could not find a valid gem 'activerecord-postgresql-adapter' (>= 0) in any repository
ERROR: Possible alternatives: activerecord-postgis-adapter, activerecord-jdbcpostgresql-adapter, activerecord-postgresql-cursors, activerecord-jdbcmysql-adapter, activerecord-jdbcmssql-adapter
which already seems weird... so what exact gem should I install to get this thing working if not what they say I should install??
When I try installing gem pg i get:
Building native extensions. This could take a while...
ERROR: Error installing pg:
ERROR: Failed to build gem native extension.
/Users/jerometufte/.rvm/rubies/ruby-1.9.2-p180/bin/ruby extconf.rb
checking for pg_config... no
No pg_config... trying anyway. If building fails, please try again with
--with-pg-config=/path/to/pg_config
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
Provided configuration options:
--with-opt-dir
...
I'm using SQLite3 currently. Any help greatly appreciated, this is baffling me.

Answer 1

Option 1:
Add pg to your Gemfile but skip trying to install it locally.
$ cat Gemfile
...
group :production do
# gems specifically for Heroku go here
gem "pg"
end
# Skip attempting to install the pg gem
$ bundle install --without production
Option 2 (Debian/Ubuntu):
Add pg to your Gemfile but first install the prerequisites.
$ cat Gemfile
...
group :production do
# gems specifically for Heroku go here
gem "pg"
end
# Install the pg gem's dependencies first
$ sudo apt-get install libpq-dev
# Then install the pg gem along with all the other gems
$ bundle install

Answer 2

You definitely need pg in the Gemfile for Heroku.
About the error you're getting locally: make sure you have postgres installed, run gem install pq -- --with-pg-config=[path to wherever your pg-config binary is], then bundle install.
Alternatively, if your local database is working fine (either because you're using sqlite or postgres-pr), you could put the gem 'pg' line in your Gemfile in a group called production, then bundle install --without production locally.

Answer 3

More up-to-date info: It had something to do with a different version of pg gem locally.
I already had pg in a production group (I run sqllite locally), but Heroku was still puking.
The problem went away for my new Rails 3.1 app when I:
rm Gemfile.lock
touch Gemfile
bundle install
git add .
git commit -am "wiped Gemfile.lock re-ran bundle install"
git push heroku master
worked like a charm when I then ran heroku run rake db:migrate