This tutorial shows you how build a simple Ruby application with CockroachDB using a PostgreSQL-compatible driver or ORM. We've tested and can recommend the Ruby pg driver and the ActiveRecord ORM, so those are featured here.
examples-orms repository.Before You Begin
Make sure you have already installed CockroachDB.
Step 1. Install the ActiveRecord ORM
To install ActiveRecord as well as the pg driver and a CockroachDB Ruby package that accounts for some minor differences between CockroachDB and PostgreSQL, run the following command:
$ gem install activerecord pg activerecord-cockroachdb-adapter
Step 2. Start a single-node cluster
For the purpose of this tutorial, you need only one CockroachDB node running in insecure mode:
$ cockroach start \
--insecure \
--store=hello-1 \
--host=localhost
Step 3. Create a user
In a new terminal, as the root user, use the cockroach user command to create a new user, maxroach.
$ cockroach user set maxroach --insecure
Step 4. Create a database and grant privileges
As the root user, use the built-in SQL client to create a bank database.
$ cockroach sql --insecure -e 'CREATE DATABASE bank'
Then grant privileges to the maxroach user.
$ cockroach sql --insecure -e 'GRANT ALL ON DATABASE bank TO maxroach'
Step 5. Run the Ruby code
The following code uses the ActiveRecord ORM to map Ruby-specific objects to SQL operations. Specifically, Schema.new.change() creates an accounts table based on the Account model (or drops and recreates the table if it already exists), Account.create() inserts rows into the table, and Account.all selects from the table so that balances can be printed.
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require 'active_record'
require 'pg'
require 'activerecord-cockroachdb-adapter'
# Connect to CockroachDB through ActiveRecord.
# In Rails, this configuration would go in config/database.yml as usual.
ActiveRecord::Base.establish_connection(
adapter: 'cockroachdb',
username: 'maxroach',
password: '',
database: 'bank',
host: 'localhost',
port: 26257,
)
# Define the Account model.
# In Rails, this would go in app/models/ as usual.
class Account < ActiveRecord::Base
validates :id, presence: true
validates :balance, presence: true
end
# Define a migration for the accounts table.
# In Rails, this would go in db/migrate/ as usual.
class Schema < ActiveRecord::Migration
def change
create_table :accounts, force: true do |t|
t.integer :balance
end
end
end
# Run the schema migration by hand.
# In Rails, this would be done via rake db:migrate as usual.
Schema.new.change()
# Create two accounts, inserting two rows into the accounts table.
Account.create(id: 1, balance: 1000)
Account.create(id: 2, balance: 250)
# Retrieve accounts and print out the balances
Account.all.each do |acct|
puts "#{acct.id} #{acct.balance}"
end
Then run the code:
$ ruby activerecord-basic-sample.rb
The output should be:
-- create_table(:accounts, {:force=>true})
-> 0.0361s
1 1000
2 250
To verify that the table and rows were created successfully, you can again use the built-in SQL client:
$ cockroach sql --insecure -e 'SHOW TABLES' --database=bank
+----------+
| Table |
+----------+
| accounts |
+----------+
(1 row)
$ cockroach sql --insecure -e 'SELECT id, balance FROM accounts' --database=bank
+----+---------+
| id | balance |
+----+---------+
| 1 | 1000 |
| 2 | 250 |
+----+---------+
(2 rows)
What's Next?
Read more about using the ActiveRecord ORM, or check out a more realistic implementation of ActiveRecord with CockroachDB in our examples-orms repository.
You might also be interested in using a local cluster to explore the following core CockroachDB features:
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