database-expert

Database Expert

Comprehensive guide for database design, optimization, and administration.

Database Selection

PostgreSQL

Schema Design

-- Users table with proper constraints
CREATE TABLE users (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    email VARCHAR(255) NOT NULL UNIQUE,
    password_hash VARCHAR(255) NOT NULL,
    full_name VARCHAR(100) NOT NULL,
    status VARCHAR(20) NOT NULL DEFAULT 'active'
        CHECK (status IN ('active', 'inactive', 'suspended')),
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

-- Index for common queries
CREATE INDEX idx_users_email ON users(email);
CREATE INDEX idx_users_status ON users(status) WHERE status = 'active';

-- Automatic updated_at trigger
CREATE OR REPLACE FUNCTION update_updated_at_column()
RETURNS TRIGGER AS $$
BEGIN
    NEW.updated_at = NOW();
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER update_users_updated_at
    BEFORE UPDATE ON users
    FOR EACH ROW
    EXECUTE FUNCTION update_updated_at_column();

-- Posts with full-text search
CREATE TABLE posts (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    author_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    title VARCHAR(255) NOT NULL,
    content TEXT NOT NULL,
    tags TEXT[] DEFAULT '{}',
    search_vector TSVECTOR,
    published_at TIMESTAMPTZ,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

-- Full-text search index
CREATE INDEX idx_posts_search ON posts USING GIN(search_vector);

Query Optimization

-- EXPLAIN ANALYZE for query analysis
EXPLAIN (ANALYZE, BUFFERS, FORMAT TEXT)
SELECT u.full_name, COUNT(p.id) as post_count
FROM users u
LEFT JOIN posts p ON p.author_id = u.id
WHERE u.status = 'active'
GROUP BY u.id
ORDER BY post_count DESC
LIMIT 10;

-- Partial index for filtered queries
CREATE INDEX idx_posts_published
ON posts(published_at)
WHERE published_at IS NOT NULL;

-- Covering index (index-only scan)
CREATE INDEX idx_posts_author_title
ON posts(author_id)
INCLUDE (title, published_at);

-- Expression index
CREATE INDEX idx_users_email_lower
ON users(LOWER(email));