Conventions for using PostgreSQL, a relational database, and for writing database migrations, which are controlled changes to a database's structure.

Use them when adding tables or columns, changing constraints, creating relationships, choosing PostgreSQL data types, or preparing migrations for existing data.

They help keep schema changes reversible, indexed, linked correctly, and safe to apply while the application is running.

database — Cursor rule for Cursor by romkey/I2C-Directory

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo

git clone --depth 1 https://github.com/romkey/I2C-Directory

Made for: Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/rules/romkey/i2c-directory/database/github.svg)](https://agentmods.dev/rules/romkey/i2c-directory/database)

Your own site

<a href="https://agentmods.dev/rules/romkey/i2c-directory/database"><img src="https://agentmods.dev/badge/rules/romkey/i2c-directory/database/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/rules/romkey/i2c-directory/database"><img src="https://agentmods.dev/badge/rules/romkey/i2c-directory/database.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 0 Nothing until a file matches its globs; then the whole rule loads.

When invoked 285 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00000	$0.00285
Opus 5.5	$0.00000	$0.00114
Sonnet 5.5	$0.00000	$0.00057
Haiku 4.5	$0.00000	$0.00028

Measured 1mo ago against content hash 422852495c33, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

database scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/database.mdc · 30 lines

What it actually says

Database and Migrations

Database: PostgreSQL 16
Adapter: pg gem with connection via DATABASE_URL or individual DB_HOST/DB_PORT/DB_USERNAME/DB_PASSWORD env vars

Migration Conventions

Always provide a reversible migration or implement both up and down methods
Use add_index for columns used in WHERE, ORDER BY, or JOIN clauses
Use add_reference with foreign_key: true for associations
Prefer change_column_null over allowing nullable columns by default — be explicit
Use PostgreSQL-specific types when beneficial: citext for case-insensitive text, jsonb for JSON data, uuid for external IDs
Add NOT NULL constraints with defaults for new required columns on existing tables to avoid downtime

# ✅ Safe addition of a required column to an existing table
class AddStatusToMembers < ActiveRecord::Migration[8.0]
  def change
    add_column :members, :status, :string, null: false, default: 'active'
    add_index :members, :status
  end
end

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

1mo ago First seen · 30 lines · 0 tokens per session scan A 422852495c33

Subscribe to this mod's changes

database is a cursor rule published in the GitHub repository romkey/I2C-Directory (11 stars, last pushed 11d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 285 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Databases PostgreSQL arduino esp32 esp8266 i2c i2c-bus twowire

database

Getting it into your agent

Wrote this? Show the measurements

What it costs to keep this loaded

Grade A, and why

Nothing flagged

What it actually says

Database and Migrations

Migration Conventions

What this file has done since we first saw it

Other cursor rules, from other repositories

adapter-features

unit-tests-tdd

planning-and-delegation

integration-tests

postgresql

netlify-database-migration-from-extension