database

A review of database queries, schema changes, migrations, and indexes.

In plain words
What is it for?
Use it to assess query execution plans, filters, joins, schema design, migrations, foreign keys, constraints, and data integrity.
Why use it?
It exposes slow queries, missing indexes, weak constraints, poor data types, and other problems that may only appear with production-sized data.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/dean0x/devflow/database
Any agent
npx skills add dean0x/devflow --skill database
Clone the repo
git clone --depth 1 https://github.com/dean0x/devflow

Made for: Claude Code, Codex.

Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,069 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00020 $0.01069
Opus 5 $0.00010 $0.00535
Sonnet 5 $0.00004 $0.00214
Haiku 4.5 $0.00002 $0.00107

Measured yesterday against content hash f87d12d7aa63, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, 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 yesterday.

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.

src/assets/skills/database/SKILL.md · 135 lines

How it starts

The opening of the file, as written. The whole thing — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Database Patterns

Domain expertise for database design and optimization. Use alongside devflow:review-methodology for complete database reviews.

Iron Law

EVERY QUERY MUST HAVE AN EXECUTION PLAN

Never deploy a query without understanding its execution plan. Every WHERE clause needs an index analysis. Every JOIN needs cardinality consideration. "It works in dev" is not validation. Production data volumes will expose every missing index and inefficient join.

Database Categories

1. Schema Design Issues

Issue Problem Solution
Missing Foreign Keys No referential integrity, orphaned records Add FK with ON DELETE action
Denormalization Unnecessary duplication, update anomalies Normalize unless performance requires
Poor Data Types VARCHAR for everything, lost precision Use appropriate types (DECIMAL, BOOLEAN, TIMESTAMP)
Missing Constraints No data validation at DB level Add NOT NULL, CHECK, UNIQUE constraints

Example - Missing Constraints:

-- VIOLATION
CREATE TABLE products (id SERIAL, name VARCHAR(100), price DECIMAL);

-- CORRECT
CREATE TABLE products (
  id SERIAL PRIMARY KEY,
  name VARCHAR(100) NOT NULL CHECK (LENGTH(TRIM(name)) > 0),
  price DECIMAL(10, 2) NOT NULL CHECK (price >= 0)
);

2. Query Optimization Issues

Issue Problem Solution
N+1 Queries Query per iteration, O(n) round trips JOIN or batch with IN/ANY
Missing Indexes Full table scans on large tables Add indexes for WHERE/JOIN columns
Full Table Scans Functions prevent index use Functional indexes or query rewrite
Inefficient JOINs Joining before filtering Filter early, select specific columns

Example - N+1 Query:

// VIOLATION: 101 queries for 100 users
for (const user of users) {
  user.orders = await db.query('SELECT * FROM orders WHERE user_id = ?', [user.id]);
}

// CORRECT: 2 queries total
const orders = await db.query('SELECT * FROM orders WHERE user_id = ANY($1)', [userIds]);

Read the full file on GitHub · 135 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

  1. yesterday First seen · 135 lines · 20 tokens per session scan A f87d12d7aa63

Subscribe to this mod's changes

database is a skill published in the GitHub repository dean0x/devflow (19 stars, last pushed 2d ago), licensed MIT. It adds 20 tokens to every session and 1,069 once invoked, about $0.0001 per session on Opus 5. 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.

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