Connect to PostgreSQL Data in Ruby

The CData ODBC Driver for PostgreSQL makes it easy to integrate connectivity to live PostgreSQL data in Ruby. This article shows how to create a simple Ruby app that connects to PostgreSQL data, executes a query, and displays the results.

Create an ODBC Connection to PostgreSQL Data

If you have not already, first specify connection properties in an ODBC DSN (data source name). This is the last step of the driver installation. You can use the Microsoft ODBC Data Source Administrator to create and configure ODBC DSNs.

To connect to PostgreSQL, set the Server, Port (the default port is 5432), and Database connection properties and set the User and Password you wish to use to authenticate to the server. If the Database property is not specified, the data provider connects to the user's default database.

SSH Connectivity for PostgreSQL

You can use SSH (Secure Shell) to authenticate with PostgreSQL, whether the instance is hosted on-premises or in supported cloud environments. SSH authentication ensures that access is encrypted (as compared to direct network connections).

SSH Connections to PostgreSQL in Password Auth Mode

To connect to PostgreSQL via SSH in Password Auth mode, set the following connection properties:

• User: PostgreSQL User name
• Password: PostgreSQL Password
• Database: PostgreSQL database name
• Server: PostgreSQL Server name
• Port: PostgreSQL port number like 3306
• UserSSH: "true"
• SSHAuthMode: "Password"
• SSHPort: SSH Port number
• SSHServer: SSH Server name
• SSHUser: SSH User name
• SSHPassword: SSH Password

SSH Connections to PostgreSQL in Public Key Auth Mode

To connect to PostgreSQL via SSH in Password Auth mode, set the following connection properties:

• User: PostgreSQL User name
• Password: PostgreSQL Password
• Database: PostgreSQL database name
• Server: PostgreSQL Server name
• Port: PostgreSQL port number like 3306
• UserSSH: "true"
• SSHAuthMode: "Public_Key"
• SSHPort: SSH Port number
• SSHServer: SSH Server name
• SSHUser: SSH User name
• SSHClientCret: the path for the public key certificate file

Installing Ruby and Necessary Gems

If you do not have Ruby installed, refer to the Ruby installation page. With Ruby installed, you will need to install the ruby-dbi, dbd-odbc, and ruby-odbc gems:

gem install dbi
gem install dbd-odbc
gem install ruby-odbc

Create a Ruby App with Connectivity to PostgreSQL Data

Create a new Ruby file (for example: PostgreSQLSelect.rb) and open it in a text editor. Copy the following code into your file:

#connect to the DSN
require 'dbi'
cnxn = DBI.connect('DBI:ODBC:CData PostgreSQL Source','','')

#execute a SELECT query and store the result set
resultSet = cnxn.execute("SELECT ShipName, ShipCity FROM Orders")

#display the names of the columns
resultSet.column_names.each do |name|
  print name, "\t"
end
puts

#display the results
while row = resultSet.fetch do
  (0..resultSet.column_names.size - 1).each do |n|
    print row[n], "\t"
  end
  puts
end
resultSet.finish

#close the connection
cnxn.disconnect if cnxn

With the file completed, you are ready to display your PostgreSQL data with Ruby. To do so, simply run your file from the command line:

ruby PostgreSQLSelect.rb

Writing SQL-92 queries to PostgreSQL allows you to quickly and easily incorporate PostgreSQL data into your own Ruby applications. Download a free trial today!