Configure Database Connection

This guide shows you how to configure your database connection in CQL.

Basic PostgreSQL Connection

require "cql"
require "pg"

MyDB = CQL::Schema.define(
  :my_db,
  adapter: CQL::Adapter::Postgres,
  uri: "postgres://username:password@localhost:5432/myapp_development"
) do
end

MyDB.init

Basic SQLite Connection

require "cql"
require "sqlite3"

MyDB = CQL::Schema.define(
  :my_db,
  adapter: CQL::Adapter::SQLite,
  uri: "sqlite3://./db/development.db"
) do
end

MyDB.init

Basic MySQL Connection

require "cql"
require "mysql"

MyDB = CQL::Schema.define(
  :my_db,
  adapter: CQL::Adapter::MySql,
  uri: "mysql://username:password@localhost:3306/myapp_development"
) do
end

MyDB.init

Use Environment Variables

DATABASE_URL = ENV["DATABASE_URL"]? || "postgres://localhost/myapp_development"

MyDB = CQL::Schema.define(
  :my_db,
  adapter: CQL::Adapter::Postgres,
  uri: DATABASE_URL
) do
end

Connection String Format

PostgreSQL

postgres://username:password@host:port/database
postgres://user:pass@localhost:5432/myapp
postgres://localhost/myapp  # Uses default user and port

MySQL

mysql://username:password@host:port/database
mysql://user:pass@localhost:3306/myapp

SQLite

sqlite3://path/to/database.db
sqlite3://./db/development.db
sqlite3://:memory:  # In-memory database

Test Connection

begin
  MyDB.init
  puts "Connected successfully"
rescue ex
  puts "Connection failed: #{ex.message}"
  exit 1
end

Connection with Options (PostgreSQL)

MyDB = CQL::Schema.define(
  :my_db,
  adapter: CQL::Adapter::Postgres,
  uri: "postgres://user:pass@localhost:5432/myapp?sslmode=require"
) do
end

Create Database Directory (SQLite)

db_path = "./db/development.db"
Dir.mkdir_p(File.dirname(db_path)) unless Dir.exists?(File.dirname(db_path))

MyDB = CQL::Schema.define(
  :my_db,
  adapter: CQL::Adapter::SQLite,
  uri: "sqlite3://#{db_path}"
) do
end

Multiple Databases

PrimaryDB = CQL::Schema.define(
  :primary,
  adapter: CQL::Adapter::Postgres,
  uri: ENV["PRIMARY_DATABASE_URL"]
) do
end

AnalyticsDB = CQL::Schema.define(
  :analytics,
  adapter: CQL::Adapter::Postgres,
  uri: ENV["ANALYTICS_DATABASE_URL"]
) do
end

# Use different schemas for different models
struct User
  db_context PrimaryDB, :users
end

struct PageView
  db_context AnalyticsDB, :page_views
end

Verify Connection

MyDB.init

# Run a simple query
MyDB.exec("SELECT 1")
puts "Database connection verified"

Related

• Configure Multiple Environments

• Set Up Connection Pooling

• Enable SSL Connections