postgresql

name: postgresql description: PostgreSQL relational database with JSONB, CTEs, window functions, and extensions. Use for SQL queries.

PostgreSQL (Postgres) is a powerful, open-source object-relational database system. It is known for its reliability, feature robustness (JSONB, GIS, Full Text Search), and performance.

When to Use

Primary Database: The default choice for almost any modern application (Django, Rails, Node).
Complex Data: When you need Relational + JSON (NoSQL) + Geo-spatial (PostGIS) in one DB.
Data Integrity: When strictly typed schemas and ACID compliance are critical.

Quick Start

-- JSONB column usage
CREATE TABLE events (
    id SERIAL PRIMARY KEY,
    data JSONB
);

INSERT INTO events (data) VALUES ('{"type": "login", "user": "alice"}');

-- Query JSON directly (indexing supported)
SELECT * FROM events WHERE data->>'user' = 'alice';

Core Concepts

JSONB

Binary JSON storage. Faster to process and allows indexing.

CREATE INDEX idx_data ON events USING GIN (data);

Common Table Expressions (CTEs)

Readable complex queries using WITH.

WITH regional_sales AS (
    SELECT region, SUM(amount) AS total_sales
    FROM orders
    GROUP BY region
)
SELECT * FROM regional_sales WHERE total_sales > (SELECT SUM(total_sales)/10 FROM regional_sales);

MVCC (Multi-Version Concurrency Control)

Postgres handles simultaneous access by keeping multiple versions of a row. Readers don't block writers, and writers don't block readers.

Best Practices (2025)

Do:

Use pgvector: For AI/ML vector embeddings storage (Postgres 17+ optimizations).
Use GENERATE_SERIES: Great for generating test data or filling gaps in time-series reports.
Tune work_mem: Default is low (4MB). Increase specific session work_mem for complex complex sort/hash operations.

Don't:

Don't use NOT IN with NULLs: It often behaves counter-intuitively. Use NOT EXISTS.
Don't skip VACUUM: Although autovacuum is good, heavy write loads may need tuning.