Ruby on Rails connection guide
Rails PostgreSQL Connection String
Configure Rails with DATABASE_URL, understand how it merges with database.yml, and test the connection before a deploy.
Use the connection value generated by Ruby on Rails, keep it in an environment variable, and test it before changing application code. The URI shape below is a template, not a credential to paste unchanged.
- URI scheme
- postgresql://
- Default PostgreSQL port
- 5432
- Credential handling
- Environment variable or secret manager
- First test
- bin/rails db:version
Connection string template
postgresql://USER:PASSWORD@HOST:5432/DB_NAME?pool=5Replace every uppercase placeholder. Percent-encode reserved characters in URI usernames and passwords.
Environment variable
DATABASE_URL="postgresql://USER:PASSWORD@HOST:5432/DB_NAME"Where to get the Ruby on Rails values
Rails reads DATABASE_URL automatically. A production database.yml can use url: <%= ENV.fetch("DATABASE_URL") %> and set the pool from RAILS_MAX_THREADS.
The failure mode worth checking first
If database.yml and DATABASE_URL both contain connection values, Rails merges them and the environment URL wins on duplicate keys. That can make a stale host in deployment settings hard to spot.
Test the connection
Run a cheap read-only command before migrations or application startup. That separates network, TLS, and authentication errors from framework configuration problems.
Connection check
bin/rails db:versionOpen it in PostgresGUI
Paste the PostgreSQL URI into PostgresGUI or enter the same host, port, database, user, password, and SSL mode as separate fields. A desktop connection is useful for checking the visible schemas and role permissions before debugging the application layer.
Questions that come up
Should the connection string be committed to Git?
No. Commit an example with placeholders and load the real value from an environment variable or secret manager.
Why does a password with @ or # break the URI?
Those characters have meaning inside a URL. Percent-encode the username and password, or use a structured connection API instead of assembling a URL by hand.
Do I need sslmode=require?
Most hosted PostgreSQL services require TLS. For strict certificate and hostname verification, use sslmode=verify-full with the provider's trusted root certificate when the client supports it.