system.part_log Introspection

The Part Log Introspection tool tracks all part-level operations in your ClickHouse cluster, including merges, mutations, downloads, and removals.

It provides multiple filters and distribution charts as well as a detail table for us to quick find queries from the UI without manually writing multiple SQLs on the system.part_log table.

Prerequisites

Note: Read access to the system.part_log table is required to use this introspection tool. Ensure your user has the necessary system table privileges.

UI

Use Cases

Merge Monitoring

1. Filter by MergeParts: Focus on merge operations
2. Monitor Duration: Sort by duration to find slow merges
3. Track Frequency: Use distribution chart to see merge patterns
4. Identify Issues: Filter by error to find failed merges

Mutation Tracking

1. Filter by MutatePart: Track ALTER operations
2. Monitor Progress: Check duration and status
3. Identify Bottlenecks: Find slow mutations
4. Error Analysis: Filter by error to debug issues

Replication Monitoring

1. Filter by DownloadPart: Track part downloads from replicas
2. Monitor Lag: Check event times to identify replication delays
3. Error Tracking: Filter by error to find replication failures
4. Node Comparison: Filter by hostname to compare nodes

Storage Analysis

1. Filter by NewPart/RemovePart: Track part lifecycle
2. Monitor Size: Sort by size_in_bytes to find large parts
3. Track Growth: Use time range to see storage trends
4. Part Type Analysis: Filter by part_type to understand storage formats

Next Steps

• Cluster Dashboard — Monitor cluster-wide metrics
• Node Dashboard — Monitor individual node metrics
• System Log Introspection — Overview of all system log tools
• system.ddl_distribution_queue Introspection — Monitor distributed DDL operations
• system.query_log Introspection — Analyze query execution logs
• system.query_views_log Introspection — Monitor query view executions