query-optimizer

A guide for finding and fixing slow PostgreSQL queries, which are commands used to read or change database data. It uses EXPLAIN ANALYZE, a PostgreSQL report showing how a query actually ran, to suggest fixes such as indexes or query changes.

In plain words
What is it for?
Use it to investigate slow queries or pages, identify missing indexes and costly operations, detect N+1 database requests, and compare timings before and after a fix.
Why use it?
It replaces guesswork with evidence about where a query spends time. It also covers common causes such as scanning too many rows and making one database request per result row.

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/m-binimran/dev-pack/query-optimizer
Any agent
npx skills add m-binimran/dev-pack --skill query-optimizer
Clone the repo
git clone --depth 1 https://github.com/m-binimran/dev-pack

Made for: Claude Code, Codex.

Per session 56 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 404 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 $0.00056 $0.00404
Opus 5 $0.00028 $0.00202
Sonnet 5 $0.00011 $0.00081
Haiku 4.5 $0.00006 $0.00040

Measured yesterday against content hash e6dc8bd37b1e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

query-optimizer 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.

skills/query-optimizer/SKILL.md · 34 lines

What it actually says

query-optimizer

Make the query fast based on evidence, not guesses.

Process

  1. Get the plan: run EXPLAIN (ANALYZE, BUFFERS) <query>. Never optimize without it.
  2. Read the plan top-down: find the costliest node. Look for:
    • Seq Scan on a big table where an index could be used.
    • Rows Removed by Filter high → missing/!selective index.
    • Estimated vs actual rows far apart → stale stats (ANALYZE).
    • Nested loop over many rows → maybe a hash/merge join is better.
  3. Propose the smallest fix: an index, a rewritten predicate, a LIMIT, or pagination.
  4. Re-measure with EXPLAIN ANALYZE and report before/after timing. Don't claim a win without it.

Common fixes

  • Composite index ordered by selectivity for multi-column filters.
  • Partial index (where active) for queries that always filter the same way.
  • Replace OFFSET pagination with keyset (where id > $last) for deep pages.
  • Kill N+1: one query per row in app code → use a join or IN (...)/= ANY.

Output

  • The plan's bottleneck in one sentence.
  • The fix (SQL/DDL).
  • Before/after timing from real EXPLAIN ANALYZE runs.

Guardrails

  • An index isn't free — it slows writes. Only add what the plan justifies.
  • Don't add an index that duplicates an existing one's prefix.
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 · 34 lines · 56 tokens per session scan A e6dc8bd37b1e

Subscribe to this mod's changes

query-optimizer is a skill published in the GitHub repository m-binimran/dev-pack (2 stars, last pushed 2mo ago), licensed MIT. It adds 56 tokens to every session and 404 once invoked, about $0.0003 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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