sql-index-review

A method for finding database indexes that can make SQL queries faster. An index is an extra data structure that helps a database find, join, or sort rows without scanning the whole table.

In plain words
What is it for?
Use it to investigate slow queries, choose indexes for filters, joins, and sorting, assess covering indexes, and verify the result with EXPLAIN.
Why use it?
It replaces guesswork with query-plan checks before and after an index change. It also helps avoid unnecessary indexes, which use storage and can slow down data changes.

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/ikarusmk/aicortex/sql-index-review
Any agent
npx skills add IkarusMK/AIcortex --skill sql-index-review
Clone the repo
git clone --depth 1 https://github.com/IkarusMK/AIcortex

Made for: Claude Code, Codex.

Per session 32 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 360 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 $0.00032 $0.00360
Opus 5 $0.00016 $0.00180
Sonnet 5 $0.00006 $0.00072
Haiku 4.5 $0.00003 $0.00036

Measured 3d ago against content hash ae9aabc22294, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

sql-index-review 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 3d 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.

examples/skills/sql-index-review/SKILL.md · 32 lines

What it actually says

SQL Index Review

When to use

A query is slow, or before shipping a query that runs hot.

Method

  1. Get the plan: EXPLAIN (ANALYZE, BUFFERS) (Postgres) / EXPLAIN (MySQL). Look for Seq Scan / full table scan on big tables, and rows estimated ≫ rows returned.
  2. Index what you filter, join, and sort on — columns in WHERE, JOIN ... ON, and ORDER BY. A composite index follows the column order of the predicate (equality columns first, then the range/sort column).
  3. Covering index: include the selected columns so the index alone answers the query (INCLUDE (...) in Postgres) — no heap fetch.
  4. Re-measure the plan after adding the index. Confirm the scan is now an index scan.

Don't

  • Over-index: every index slows writes and costs storage. Drop unused ones.
  • Index low-cardinality columns alone (e.g. a boolean) — rarely helps.
  • Wrap an indexed column in a function in WHERE (WHERE lower(email)=…) unless you built a matching expression index — it defeats the index.

Rule of thumb

Add the index that turns the most expensive Seq Scan in your hottest query into an index scan; verify with EXPLAIN before and after.

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. 3d ago First seen · 32 lines · 32 tokens per session scan A ae9aabc22294

Subscribe to this mod's changes

sql-index-review is a skill published in the GitHub repository IkarusMK/AIcortex (9 stars, last pushed 14d ago), licensed Apache-2.0. It adds 32 tokens to every session and 360 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.

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