postgres-patternslisted

# PostgreSQL Patterns Quick reference for PostgreSQL best practices: schema design, indexing, query optimization, concurrency, and security. ## When to Activate - Writing SQL queries or migrations - Designing database schemas - Troubleshooting slow queries (EXPLAIN ANALYZE) - Implementing Row Level Security - Preventing deadlocks / tuning concurrency - Setting up connection pooling ## Schema Design ### Data Type Quick Reference | Use Case | Correct Type | Avoid | |----------|-------------|-------| | IDs | `bigint` (IDENTITY) or UUIDv7 | `int`, random UUIDv4 as PK | | Strings | `text` | `varchar(255)` without reason | | Timestamps | `timestamptz` | `timestamp` (no timezone) | | Money | `numeric(10,2)` | `float` | | Flags | `boolean` | `varchar`, `int` | Rules: - Use `lowercase_snake_case` identifiers (avoid quoted mixed-case). - Define constraints explicitly: PK, FK with `ON DELETE`, `NOT NULL`, `CHECK`. - Index every foreign key — always, no exceptions. ## Indexing ### Index Cheat Sheet | Query Pattern | Index Type | Example | |--------------|------------|---------| | `WHERE col = value` | B-tree (default) | `CREATE INDEX idx ON t (col)` | | `WHERE col > value` | B-tree | `CREATE INDEX idx ON t (col)` | | `WHERE a = x AND b > y` | Composite | `CREATE INDEX idx ON t (a, b)` | | `WHERE jsonb @> '{}'` | GIN | `CREATE INDEX idx ON t USING gin (col)` | | `WHERE tsv @@ query` | GIN | `CREATE INDEX idx ON t USING gin (col)` | | Time-series ranges | BRIN | `CREATE INDEX idx