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Analyze ClickHouse cache systems including mark cache, uncompressed cache, and query cache. Use for cache hit ratio issues and cache tuning.
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SOC 職業分類に基づく
Read-only ClickHouse security audit expert for live or exported systems. Use when assessing ClickHouse security posture, reviewing users, roles, grants, settings profiles, row policies, table functions, external sources, table engines, executable UDFs, audit logs, named collections, password hash hygiene, SQL SECURITY DEFINER, impersonation, TLS/network exposure, Keeper/interserver security, encryption at rest, backups, the HTTP interface surface, cluster security, or version-specific ClickHouse security behavior. Diagnoses from SQL/system tables, supplied configuration files, query logs, access metadata, and ClickHouse/Altinity documentation.
Diagnose and resolve ClickHouse grant and authentication errors, especially after upgrades. Use when queries fail with ACCESS_DENIED/NOT_ENOUGH_PRIVILEGES, AUTHENTICATION_FAILED/WRONG_PASSWORD/REQUIRED_PASSWORD, or ON CLUSTER privilege errors; when system.* or INFORMATION_SCHEMA access is denied; or when grant behavior changes after version upgrades.
Establishes the ClickHouse connection mode, cluster macro, and default log timeframe for diagnostics. Use first, before any other altinity-expert-clickhouse skill, to verify connectivity and set shared analysis rules.
Analyze ClickHouse external dictionaries including configuration, memory usage, reload status, and performance. Use for dictionary issues and load failures.
Analyze whether ClickHouse indexes (PRIMARY KEY, ORDER BY, skipping indexes, projections) are being used effectively for actual query patterns. Use when investigating index effectiveness, ORDER BY key design, query-to-index alignment, or when queries scan more data than expected.
Diagnose ClickHouse INSERT performance, batch sizing, part creation patterns, and ingestion bottlenecks. Use for slow inserts and data pipeline issues.
| name | altinity-expert-clickhouse-caches |
| description | Analyze ClickHouse cache systems including mark cache, uncompressed cache, and query cache. Use for cache hit ratio issues and cache tuning. |
| license | Apache-2.0 |
Analyze ClickHouse cache systems: mark cache, uncompressed cache, query cache, and compiled expression cache.
Run all queries from checks.sql in this skill's directory and analyze the results.
| Cache | Typical Size | Notes |
|---|---|---|
| Mark Cache | 5-10% of RAM | Higher if random access patterns |
| Uncompressed | 0 (disabled) or 5-10% | Enable only for specific workloads |
| Query Cache | 1-5GB | For repeated identical queries |
| Compiled Expression | 128MB-1GB | Higher for complex expressions |
Possible causes:
If mark cache > 15% RAM:
Solutions:
index_granularity for tables with excessive marksmark_cache_size setting| Finding | Load Module | Reason |
|---|---|---|
| Cache using too much RAM | altinity-expert-clickhouse-memory | Overall memory analysis |
| Poor hit ratio + high disk IO | altinity-expert-clickhouse-storage | Disk bottleneck |
| Many marks per table | altinity-expert-clickhouse-schema | Consider index_granularity tuning |
| Query cache misses | altinity-expert-clickhouse-reporting | Query pattern analysis |
| Setting | Scope | Notes |
|---|---|---|
mark_cache_size | Server | Global mark cache limit |
uncompressed_cache_size | Server | Set to 0 to disable |
use_uncompressed_cache | Query | Enable per-query |
query_cache_max_size | Server | Query result cache |
use_query_cache | Query | Enable per-query |