Memory usage and OOM diagnostics

Answers "where is the RAM going, and what will OOM next?" from system.asynchronous_metrics, system.metrics, system.dictionaries, system.parts, system.server_settings and system.query_log. Run altinity-expert-clickhouse-connection first if the connection mode, cluster and time window are not yet established.

Query packs

• checks.sql — 15 checks: RAM total vs ClickHouse resident, component breakdown (dictionaries, Memory/Set/Join tables, primary keys, caches), allocation audit, top memory consumers among queries, dictionaries, Memory-engine tables and primary keys, memory over time, MEMORY_LIMIT_EXCEEDED exceptions, a query plus part_log memory timeline, server memory settings, memory used by non-ClickHouse processes, and high-memory GROUP BY and JOIN query shapes. Check memory-08 needs system.asynchronous_metric_log and memory-11 needs system.part_log; skip them when those tables are absent.
• 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.