shell

nself db shell

Category: Database Commands

Open an interactive PostgreSQL shell (psql) connected to your nself database.

Overview

Provides direct SQL access to your PostgreSQL database for querying, administration, and debugging.

Features:

• ✅ Automatic connection to project database
• ✅ psql with full features (history, tab completion)
• ✅ Hot execution (no restart needed)
• ✅ Environment-aware (connects to correct database per ENV)
• ✅ Run SQL files directly

Usage

nself db shell [OPTIONS] [SQL_FILE]

Options

Option	Description
-c, --command SQL	Execute single SQL command
-f, --file FILE	Execute SQL from file
--readonly	Connect as read-only user
-v, --verbose	Show detailed output

Arguments

Argument	Description
SQL_FILE	Optional: SQL file to execute

Examples

Interactive Shell

nself db shell

Output:

psql (15.3)
Type "help" for help.

myapp_db=# SELECT * FROM users LIMIT 5;
 id |    email           | created_at
----+--------------------+------------
  1 | user1@example.com  | 2026-02-01
  2 | user2@example.com  | 2026-02-02
(2 rows)

myapp_db=# \dt
         List of relations
 Schema |     Name     | Type  |  Owner
--------+--------------+-------+---------
 public | users        | table | postgres
 public | roles        | table | postgres
 public | permissions  | table | postgres
(3 rows)

myapp_db=# \q

Execute Single Command

nself db shell -c "SELECT COUNT(*) FROM users;"

Output:

 count
-------
   142
(1 row)

Execute SQL File

nself db shell -f scripts/analytics.sql

Output:

→ Executing: scripts/analytics.sql
 user_count | order_count | revenue
------------+-------------+---------
        142 |        1523 | 45328.50
(1 row)

✓ Script executed successfully

Read-Only Access

nself db shell --readonly

Use when:

• Querying production data
• Preventing accidental modifications
• Running analytics queries

Common psql Commands

Meta Commands

-- List all tables
\dt

-- Describe table structure
\d users

-- List all schemas
\dn

-- List all databases
\l

-- List all roles
\du

-- Show current connection info
\conninfo

-- List all indexes
\di

-- Execute SQL from file
\i path/to/file.sql

-- Toggle timing
\timing

-- Quit
\q

Useful Queries

-- Table sizes
SELECT
  schemaname,
  tablename,
  pg_size_pretty(pg_total_relation_size(schemaname||'.'||tablename))
FROM pg_tables
WHERE schemaname NOT IN ('pg_catalog', 'information_schema')
ORDER BY pg_total_relation_size(schemaname||'.'||tablename) DESC;

-- Active connections
SELECT
  pid,
  usename,
  application_name,
  client_addr,
  state,
  query
FROM pg_stat_activity
WHERE datname = current_database();

-- Database size
SELECT pg_size_pretty(pg_database_size(current_database()));

-- Recent queries
SELECT
  query,
  calls,
  total_time,
  mean_time
FROM pg_stat_statements
ORDER BY total_time DESC
LIMIT 10;

Running Complex Queries

Multi-line Queries

myapp_db=# SELECT
myapp_db-#   users.email,
myapp_db-#   COUNT(orders.id) as order_count
myapp_db-# FROM users
myapp_db-# LEFT JOIN orders ON users.id = orders.user_id
myapp_db-# GROUP BY users.email
myapp_db-# HAVING COUNT(orders.id) > 10;

Transactions

BEGIN;

UPDATE users SET status = 'active' WHERE id = 123;
UPDATE user_stats SET last_login = NOW() WHERE user_id = 123;

COMMIT;
-- Or ROLLBACK; to undo

Import/Export

-- Export to CSV
\copy (SELECT * FROM users) TO '/tmp/users.csv' CSV HEADER;

-- Import from CSV
\copy users FROM '/tmp/users.csv' CSV HEADER;

-- Export with query
\copy (SELECT * FROM users WHERE created_at > '2026-01-01') TO '/tmp/recent_users.csv' CSV HEADER;

Database Introspection

Table Information

nself db shell -c "\d+ users"

Shows:

• Column names and types
• Constraints (PRIMARY KEY, FOREIGN KEY, UNIQUE)
• Indexes
• Triggers
• Table size

Constraint Information

nself db shell -c "SELECT conname, contype FROM pg_constraint WHERE conrelid = 'users'::regclass;"

Index Usage Statistics

nself db shell -c "SELECT schemaname, tablename, indexname, idx_scan FROM pg_stat_user_indexes ORDER BY idx_scan DESC;"

Troubleshooting

Connection refused

Error:

psql: error: connection to server failed: Connection refused

Solutions:

# Check if PostgreSQL is running
nself status postgres

# If not running
nself start postgres

# Check port
grep POSTGRES_PORT .env

Permission denied

Error:

ERROR: permission denied for table users

Solutions:

# Check user permissions
nself db shell -c "\du"

# Grant permissions (as admin)
nself db shell -c "GRANT ALL PRIVILEGES ON TABLE users TO myuser;"

Database does not exist

Error:

FATAL: database "myapp_db" does not exist

Solutions:

# Check database name in .env
grep POSTGRES_DB .env

# Create database if missing
nself db shell -c "CREATE DATABASE myapp_db;"

# Or reset and reinitialize
nself db reset
nself db migrate up

Query timeout

Error:

ERROR: canceling statement due to statement timeout

Solutions:

-- Increase timeout for session
SET statement_timeout = '60s';

-- Or globally (requires restart)
ALTER DATABASE myapp_db SET statement_timeout = '60s';

Environment-Specific Shell

Development

nself db shell
# Connects to dev database (from .env.dev or .env.local)

Staging

nself env switch staging
nself db shell
# Connects to staging database

Production

nself env switch prod
nself db shell --readonly
# Read-only recommended for production

Automation and Scripts

Automated Reporting

# Daily user report
nself db shell -f reports/daily-users.sql > /tmp/daily-report.txt

# Email report
nself db shell -f reports/weekly-stats.sql | mail -s "Weekly Stats" admin@example.com

Health Checks

# Check if database is accessible
if nself db shell -c "SELECT 1" > /dev/null 2>&1; then
  echo "Database OK"
else
  echo "Database ERROR"
  exit 1
fi

Data Validation

# Verify migrations
nself db shell -c "SELECT version FROM schema_migrations ORDER BY version;"

# Check for data integrity issues
nself db shell -f scripts/integrity-check.sql

Safety Tips

1. Always Use Transactions for Updates

BEGIN;
-- Your UPDATE/DELETE statements
-- Verify changes with SELECT
COMMIT;  -- Or ROLLBACK if wrong

2. Test Queries with LIMIT First

-- Test with small dataset first
SELECT * FROM users WHERE status = 'inactive' LIMIT 5;

-- Then run full query
DELETE FROM users WHERE status = 'inactive';

3. Backup Before Bulk Changes

# Backup before major changes
nself db backup before-bulk-update.sql

# Make changes
nself db shell -f bulk-update.sql

# If problems, restore
nself db restore backups/before-bulk-update.sql

4. Use EXPLAIN for Performance

EXPLAIN ANALYZE
SELECT * FROM users
WHERE email LIKE '%@example.com'
ORDER BY created_at DESC
LIMIT 100;

Related Commands

• nself db migrate - Apply schema migrations
• nself db seed - Load seed data
• nself db backup - Backup database before queries
• nself db restore - Restore if something goes wrong

See Also

• Database Management
• Migration Guide
• PostgreSQL Documentation
• psql Guide