# schema-foreign-key-indexes

> Postgres does not automatically index foreign key columns. Missing indexes cause slow JOINs and CASCADE operations.

- Source: https://doutorai.pt/en/components/skills__schema-foreign-key-indexes
- Type: Skills
- Category: Databases
- Downloads: 0
- Site: Doutor AI (https://doutorai.pt/en) - AI tools for small businesses

An open-source community component, curated and adapted by Doutor AI.

## What it does and how to use it

A **skill** that teaches Claude Code to do databases tasks well. It is packaged knowledge the model uses whenever it is relevant.

1. Install the skill (command above).
2. In Claude Code, describe what you need - the skill turns on by itself when the context fits.
3. No commands to memorize: you talk in plain language and the skill does the rest.

## Install (Claude Code)

```bash
mkdir -p .claude/skills/schema-foreign-key-indexes && curl -fsSL https://doutorai.pt/data/lib/skills__schema-foreign-key-indexes.md -o .claude/skills/schema-foreign-key-indexes/SKILL.md
```

Paste this command into the terminal, in your project folder, and the component installs automatically.

## Content

````
---
title: Index Foreign Key Columns
impact: HIGH
impactDescription: 10-100x faster JOINs and CASCADE operations
tags: foreign-key, indexes, joins, schema
---

## Index Foreign Key Columns

Postgres does not automatically index foreign key columns. Missing indexes cause slow JOINs and CASCADE operations.

**Incorrect (unindexed foreign key):**

```sql
create table orders (
  id bigint generated always as identity primary key,
  customer_id bigint references customers(id) on delete cascade,
  total numeric(10,2)
);

-- No index on customer_id!
-- JOINs and ON DELETE CASCADE both require full ta

- 🔒 Full content on the Pro plan (€7.99/month) -
````

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Content by Doutor AI (https://doutorai.pt/en). When quoting, please cite the source: https://doutorai.pt/en/components/skills__schema-foreign-key-indexes