Could not load 'active_record/connection_adapters/redshift_adapter' - ruby

Question

I ran into the error when I tried to run SQL through ruby script. Can someone help me figure out what could be the cause? I already looked for some similar posts but couldn't find the right solution yet.
/Users/User/.rbenv/versions/2.4.3/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require': Could not load 'active_record/connection_adapters/redshift_adapter'. Make sure that the adapter in config/database.yml is valid. If you use an adapter other than 'mysql', 'mysql2', 'postgresql' or 'sqlite3' add the necessary adapter gem to the Gemfile. (LoadError)
from /Users/User/.rbenv/versions/2.4.3/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `block in require'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:240:in `load_dependency'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `require'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/pg-0.17.1/lib/pg.rb:4:in `<top (required)>'
from /Users/User/.rbenv/versions/2.4.3/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require'
from /Users/User/.rbenv/versions/2.4.3/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `block in require'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:240:in `load_dependency'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `require'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activerecord4-redshift-adapter-0.2.1/lib/active_record/connection_adapters/redshift_adapter.rb:17:in `<top (required)>'
from /Users/User/.rbenv/versions/2.4.3/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:133:in `require'
from /Users/User/.rbenv/versions/2.4.3/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:133:in `rescue in require'
from /Users/User/.rbenv/versions/2.4.3/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:39:in `require'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `block in require'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:240:in `load_dependency'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `require'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activerecord-4.2.10/lib/active_record/connection_adapters/connection_specification.rb:175:in `spec'
from /Users/User/.rvm/gems/ruby-2.4.3/gems/activerecord-4.2.10/lib/active_record/connection_handling.rb:50:in `establish_connection'
from /Users/User/Desktop/github/tracker/app/workers/appsflyer_importer_worker_aggregate.rb:100:in `fetch_data'
from /Users/User/Desktop/github/tracker/app/workers/appsflyer_importer_worker_aggregate.rb:120:in `perform'
from -:30:in `<main>'
Here is my settings:
Gemfile
ruby '2.4.3'
gem 'activerecord4-redshift-adapter', '~> 0.2'
gem 'pg'
Ruby version
ruby 2.4.3p205 (2017-12-14 revision 61247) [x86_64-darwin17]
Gem list
activerecord (4.2.10, 4.2.8)
activerecord4-redshift-adapter (0.2.1)
pg (1.0.0, 0.17.1)
Script
require 'active_record'
conn = {
adapter: 'redshift',
database: '#database',
host: '#host',
port: 5439,
username: '#username',
password: '#password'
}
ActiveRecord::Base.establish_connection(conn)
sql = 'select count(*) from table'
ActiveRecord::Base.connection.execute(sql)

Answer 1

You're using the pg gem version 1.0.0 and it is not compatible with the version of active_record and activerecord4-redshift-adapter that you're using:
The PGconn, PGresult, and PGError constants are deprecated, and will be removed as of version 1.0.
This can be seen in the history of the pg gem.
The activerecord4-redshift-adapter uses both the PGconn and PGError constants:
def connection_active?
#connection.status == PGconn::CONNECTION_OK
rescue PGError
false
end
Although I was unable to exactly duplicate the error message that you saw, by modifying the Gemfile to use an older version of the pg gem I was able to get farther along:
gem 'pg', '~> 0.21'
My exact steps were:
create the Gemfile
create a file test.rb containing your Ruby code
run bundle install
run bundle exec ruby test.rb
This produces the following error:
/Users/test/.rvm/gems/ruby-2.4.3/gems/activerecord4-redshift-adapter-0.2.1/lib/active_record/connection_adapters/redshift_adapter.rb:568:in `initialize': could not translate host name "#host" to address: nodename nor servname provided, or not known (PG::ConnectionBad)
This is almost certainly in the right direction for the problem you're having, and should put you on the path to accomplishing your goal.