generating-clickhouse-query-performance-reports
Produce and structure slow-query performance reports for PostHog's production ClickHouse (US and EU). Use when asked for a slow query report, query performance analysis over the last N days, per-team query cost, OOM or timeout investigation, cluster cost/memory regressions, or materialization candidates. Covers the modern `query_log_archive` source (typed `lc_*` columns, multi-day retention), how to categorize and attribute slow queries, root-cause patterns (unmaterialized JSONExtract, high-cardinality breakdowns, heavy joins), and the report structure. Runs queries via the `query-clickhouse-via-metabase` skill.
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92%
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Low
Low-risk findings worth noting
Low
Low-risk findings.
1 low severity finding. Worth noting, but not necessarily harmful.
W011: Third-party content exposure detected (indirect prompt injection risk).
What this means
The skill exposes the agent to untrusted, user-generated content from public third-party sources, creating a risk of indirect prompt injection. This includes browsing arbitrary URLs, reading social media posts or forum comments, and analyzing content from unknown websites.
Why it was flagged
The workflow pulls `query`, `lc_query__query`, and related text fields from the outsider-authored ClickHouse log rows in `posthog.query_log_archive` (e.g., user/AI-written HogQL in `lc_query__query` and product/web query text in `query`), and this free text is read by the LLM when generating the report and example-focused write-up/delta and when grounding recommendations via linked query contents.
- Repository
- PostHog/posthog
- Commit
d1dd198
- Audited
- Security analysis
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