romankovsv/claude-code-python-devops-mlops/postgres-patterns

-- Composite Index (equality first, then range)
CREATE INDEX idx ON orders (status, created_at);
 
-- Covering Index
CREATE INDEX idx ON users (email) INCLUDE (name, created_at);
 
-- Partial Index
CREATE INDEX idx ON users (email) WHERE deleted_at IS NULL;
 
-- UPSERT
INSERT INTO settings (user_id, key, value) VALUES (123, 'theme', 'dark')
ON CONFLICT (user_id, key) DO UPDATE SET value = EXCLUDED.value;
 
-- Cursor Pagination (O(1) vs OFFSET O(n))
SELECT * FROM products WHERE id > $last_id ORDER BY id LIMIT 20;
 
-- Queue Processing
UPDATE jobs SET status = 'processing'
WHERE id = (
  SELECT id FROM jobs WHERE status = 'pending'
  ORDER BY created_at LIMIT 1
  FOR UPDATE SKIP LOCKED
) RETURNING *;

-- Find unindexed foreign keys
SELECT conrelid::regclass, a.attname
FROM pg_constraint c
JOIN pg_attribute a ON a.attrelid = c.conrelid AND a.attnum = ANY(c.conkey)
WHERE c.contype = 'f'
  AND NOT EXISTS (
    SELECT 1 FROM pg_index i WHERE i.indrelid = c.conrelid AND a.attnum = ANY(i.indkey)
  );
 
-- Find slow queries
SELECT query, mean_exec_time, calls FROM pg_stat_statements
WHERE mean_exec_time > 100 ORDER BY mean_exec_time DESC;