code-review-db

A database code-review rule set covering queries, indexes, transactions, migrations and connection pools. A database stores and retrieves an application's persistent data.

In plain words
What is it for?
Reviewing database and persistence code for N+1 queries, missing limits or indexes, inefficient data fetching, transaction scope, migration safety and pooling.
Why use it?
It helps catch slow queries, accidental mass updates or deletes, unsafe schema changes and connection-management problems before they reach production.

Cursor rule for Cursor

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 rules/andr-ca/agentharness/code-review-db
Clone the repo
git clone --depth 1 https://github.com/andr-ca/agentharness

Made for: Cursor.

Per session 46 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 925 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 $0.00046 $0.00925
Opus 5 $0.00023 $0.00463
Sonnet 5 $0.00009 $0.00185
Haiku 4.5 $0.00005 $0.00093

Measured yesterday against content hash f6174050ff15, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

code-review-db 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.

.cursor/rules/code-review-db.mdc · 52 lines

How it starts

The opening of the file, as written. The whole thing — 52 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Code Review — Database & Persistence Layer

Focus on performance, correctness, and safety at the data layer.

Query Correctness

  • N+1 queries — a loop that loads related records per item. Look for for item in items: item.related. Fix with eager loading (select_related, include, JOIN) or a batch fetch outside the loop.
  • Unbounded queriesfind_all(), SELECT * with no LIMIT, WHERE 1=1. Every read from a growing table needs pagination or a LIMIT.
  • Missing WHERE clause — an UPDATE or DELETE with no filter deletes/updates every row.
  • Implicit full-table scan — a WHERE on a column with no index. Check EXPLAIN output or migration history.
  • Fetching more columns than neededSELECT * when only 2 columns are used. Unnecessary data transfer and harder to cache.

Index Strategy

  • Missing index on foreign keyFK columns not in an index cause full scans on JOIN and cascade operations.
  • Missing index on WHERE/ORDER BY columns — any column used in a filter, sort, or join should have an index unless the table is tiny (<1k rows).
  • Index on every column — over-indexing slows writes. Indexes serve reads; add them only for proven query patterns.
  • Composite index column order — a composite index on (A, B, C) helps queries filtering A, or A+B, but NOT B alone. Confirm the index covers the actual query.
  • Index on high-cardinality boolean — a boolean column index is almost never useful (50/50 selectivity).

Transactions & Consistency

  • Two writes without a transaction — if the second write fails, the first is orphaned. Wrap in a transaction.
  • Transaction too wide — a transaction that spans an HTTP call, a file system operation, or a sleep holds locks and causes contention. Keep transactions as short as possible.
  • Read-your-own-writes — reading back a record inside a write transaction without using the same transaction/session. Causes stale reads in read-replica setups.
  • Lost update — two concurrent reads followed by two concurrent writes without optimistic or pessimistic locking.
  • Missing rollback on error — exception handling that logs and continues without rolling back a partially-committed transaction.

Read the full file on GitHub · 52 lines

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 · 52 lines · 46 tokens per session scan A f6174050ff15

Subscribe to this mod's changes

code-review-db is a cursor rule published in the GitHub repository andr-ca/agentharness (1 stars, last pushed yesterday), licensed MIT. It adds 46 tokens to every session and 925 once invoked, about $0.0002 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 2026-08-31.