Installation from source guide missing instructions for pg_trgm extension creation

Walking through the installation from source guide the following error was thrown when running the setup rake task:

/home/git/gitlab# sudo -u git -H bundle exec rake gitlab:setup RAILS_ENV=production
This will create the necessary database tables and seed the database.
You will lose any previous data stored in the database.
Do you want to continue (yes/no)? yes

-- enable_extension("plpgsql")
   -> 0.0124s
-- enable_extension("pg_trgm")
rake aborted!
ActiveRecord::StatementInvalid: PG::UndefinedFile: ERROR:  could not open extension control file "/usr/share/postgresql/9.3/extension/pg_trgm.control": No such file or directory
: CREATE EXTENSION IF NOT EXISTS "pg_trgm"

This was rectified by installing the postgresql-contrib package and creating the pg_trgm extension in the production database before continuing with the migration task as per these instructions.

sudo apt-get install postgresql-contrib
sudo -u postgres psql -d gitlabhq_production
CREATE EXTENSION pg_trgm;
\q
sudo -u git -H bundle exec rake db:migrate RAILS_ENV=production

Milestone changed to 8.8

Added ~15078 label

I followed the steps on Ubuntu 14.04, and during the db setup I got a different message:

This will create the necessary database tables and seed the database.
You will lose any previous data stored in the database.
Do you want to continue (yes/no)? yes

-- enable_extension("plpgsql")
   -> 0.0263s
-- enable_extension("pg_trgm")
rake aborted!
ActiveRecord::StatementInvalid: PG::InsufficientPrivilege: ERROR:  permission denied to create extension "pg_trgm"
HINT:  Must be superuser to create this extension.
: CREATE EXTENSION IF NOT EXISTS "pg_trgm"

I tried running sudo -u postgres psql -d gitlabhq_production -c "CREATE EXTENSION pg_trgm;", but the next time I invoked rake gitlab:setup I got the same error. Creating the extension in the template1 did the trick.

mentioned in merge request !4025 (merged)

Status changed to closed by commit d68c771a

@markglenfletcher if that's not a hassle, can you confirm that the new docs work? https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/install/installation.md#initialize-database-and-activate-advanced-features

@axil Yes, I'll walk through the new instructions

Mentioned in commit pfjason/gitlab-ce@d68c771a