Query performance analysis

Answers "which queries are slow or failing and why" from system.query_log, system.processes and system.query_views_log. Queries are grouped by normalized_query_hash, which collapses literals so one row represents a query pattern, not a single execution. Run altinity-expert-clickhouse-connection first if the connection mode, cluster and time window are not yet established.

Query packs

• checks.sql — 15 checks: currently running queries, recent performance summary, slowest queries, most frequent query patterns, queries by CPU time, queries reading too much data, queries by table accessed, recent failures and failure summary by error code, query type distribution, peak query hours, queries by user, materialized-view execution during inserts, slow materialized-view breakdown per query and distributed query performance. 2 of them need system.query_views_log.
• reference.md — background (settings, sizing, anti-patterns); read only when you need to explain a recommendation.

How to run the query packs

1. Read each pack file from this skill's directory (the skill loader prints the directory path).
2. Run statements one at a time, never a whole file. Statements end with ; and start with a -- @check <id> <title> header; keep the id with its result.
3. Honor -- @requires: skip the statement when the named table is missing, when keeper is required and the server has no Keeper/ZooKeeper, or when the version condition is not met. List skipped ids with the reason.
4. Keep {cluster} as written when a cluster macro exists; otherwise apply the connection skill's rewrite rule. Any other {placeholder} is a template variable: substitute a real value first or skip the statement.
5. On an error, record the check id and the first line of the error, then continue. Only for UNKNOWN_IDENTIFIER, run DESCRIBE TABLE system.<table> and drop the missing column.
6. A severity column is the verdict for that row. Copy it; do not re-grade.