Borrowing it
Nothing to install: this file belongs to PostHog/posthog-foss. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/PostHog/posthog-foss/master/.agents/skills/generating-clickhouse-query-performance-reports/SKILL.mdgit clone --depth 1 https://github.com/PostHog/posthog-fossWrote 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.
[](https://agentmods.dev/skills/posthog/posthog-foss/generating-clickhouse-query-performance-reports)<a href="https://agentmods.dev/skills/posthog/posthog-foss/generating-clickhouse-query-performance-reports"><img src="https://agentmods.dev/badge/skills/posthog/posthog-foss/generating-clickhouse-query-performance-reports/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.
<a href="https://agentmods.dev/skills/posthog/posthog-foss/generating-clickhouse-query-performance-reports"><img src="https://agentmods.dev/badge/skills/posthog/posthog-foss/generating-clickhouse-query-performance-reports.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 6 findings, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium Prompt Injection · line 51 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
- medium Prompt Injection · line 51 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
- medium Prompt Injection · line 54 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
- medium Prompt Injection · line 58 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
- medium Prompt Injection · line 59 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
- medium Prompt Injection · line 61 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
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 | $0.00142 | $0.04409 |
| Opus 5 | $0.00071 | $0.02204 |
| Sonnet 5 | $0.00028 | $0.00882 |
| Haiku 4.5 | $0.00014 | $0.00441 |
Grade A, and why
generating-clickhouse-query-performance-reports 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.
How it starts
The opening of the file, as written. The whole thing — 254 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Generating ClickHouse query performance reports
This skill is the methodology for investigating slow ClickHouse queries and writing up a
performance report. It pairs with querying-production-databases-via-metabase,
which is the mechanism (SSO-gated auth and hogli metabase:query). Run every query in this skill
through that one.
Reports themselves are not public. When it exists, the private PostHog/query-performance-analysis repo
holds the historical reports and example query IDs; this repo holds only the tooling and methodology.
That repo is usually checked out as a sibling folder to the posthog checkout (e.g.
../query-performance-analysis relative to the repo root, or alongside it under the same parent
directory). Look for a sibling directory named query-performance-analysis containing an analysis/
folder of dated reports. If you find it, add the new report there as a new markdown file under
analysis/, named <YYYY-MM-DD>-<topic>.md (match the existing naming, e.g.
2026-05-27-slow-queries-14d.md).
The sibling repo may not exist, and that is fine. If you cannot find it, do not write into the public
posthog repo and do not block on it: write the report to a temp folder instead (e.g.
/tmp/<YYYY-MM-DD>-<topic>.md), tell the user where you put it, and skip the previous-report comparison
in step 9 (there is no history to diff against).
Data source: posthog.query_log_archive (not system.query_log)
system.query_log on the production clusters retains only a few hours, so it cannot answer a
multi-day question. Use the Distributed archive table instead:
FROM posthog.query_log_archive
It retains roughly three weeks and exposes log_comment as typed columns, so you skip JSONExtract.
Query it directly (it already fans out across the cluster). Always filter is_initial_query so
distributed sub-queries are not double-counted. Confirm current retention with a per-day
count() before trusting a window (see references/query-patterns.md).
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.
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.
- yesterday Changed · +3 tokens per session 6f844417b491
- 9d ago First seen · 254 lines · 139 tokens per session scan A 1ad662d6e88d
generating-clickhouse-query-performance-reports is a skill published in the GitHub repository PostHog/posthog-foss (714 stars, last pushed today), licensed MIT. It adds 142 tokens to every session and 4,409 once invoked, about $0.0007 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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