Giới thiệu và Cài đặt PostgreSQL 19

# PostgreSQL 19 (mới nhất, đang Beta)
docker run --name pg19 \
  -e POSTGRES_PASSWORD=mysecretpw \
  -e POSTGRES_DB=learnpg \
  -p 5432:5432 \
  -v pgdata19:/var/lib/postgresql/data \
  -d postgres:19-beta1

# PostgreSQL 18 (stable cho production)
docker run --name pg18 \
  -e POSTGRES_PASSWORD=mysecretpw \
  -e POSTGRES_DB=learnpg \
  -p 5433:5432 \
  -v pgdata18:/var/lib/postgresql/data \
  -d postgres:18-alpine

# Kết nối
psql -h localhost -p 5432 -U postgres -d learnpg

# Connection string
psql "postgresql://postgres:mysecretpw@localhost:5432/learnpg"

-- Trong psql
CREATE DATABASE learnpg WITH ENCODING 'UTF8';
\c learnpg

CREATE TABLE greetings (
    id BIGSERIAL PRIMARY KEY,
    text TEXT NOT NULL,
    created_at TIMESTAMPTZ DEFAULT NOW()
);

INSERT INTO greetings (text) VALUES ('Xin chào PostgreSQL 19!');

SELECT * FROM greetings;

# TYPE  DATABASE  USER  ADDRESS         METHOD
host    all       all   0.0.0.0/0       scram-sha-256

SELECT pg_reload_conf();

-- Postgres database có nhiều schema (mặc định: public)
CREATE SCHEMA shop;
SET search_path TO shop, public;

-- Tạo role + grant
CREATE ROLE app_user WITH LOGIN PASSWORD 'apppwd';
GRANT CONNECT ON DATABASE learnpg TO app_user;
GRANT USAGE ON SCHEMA shop TO app_user;
GRANT SELECT, INSERT, UPDATE ON ALL TABLES IN SCHEMA shop TO app_user;

-- Xem extension có sẵn
SELECT * FROM pg_available_extensions ORDER BY name;

-- Install
CREATE EXTENSION IF NOT EXISTS "uuid-ossp";           -- UUID generator (uuid_generate_v4)
CREATE EXTENSION IF NOT EXISTS pg_trgm;               -- fuzzy search, similarity
CREATE EXTENSION IF NOT EXISTS pgcrypto;              -- crypto, hash, gen_random_uuid
CREATE EXTENSION IF NOT EXISTS postgis;               -- GIS, geometry, geography
CREATE EXTENSION IF NOT EXISTS pg_stat_statements;    -- query monitoring
CREATE EXTENSION IF NOT EXISTS vector;                -- pgvector cho AI embedding (cần install riêng)