clickhouse-query-optimization

Optimize ClickHouse queries with over 20 rules for speed and memory.

12|1|Updated Jan 30, 2026

Search Tags:#query optimization #database #data analysis #sql #performance tuning #clickhouse

Ready to run

npx skills add https://github.com/obsessiondb/clickhouse-skills --skill clickhouse-query-optimization

💬 Prompt for ChatGPT / Claude Chat▼

Please help me install this Agent Skill.
Skill: clickhouse-query-optimization
Source: https://github.com/obsessiondb/clickhouse-skills/tree/main/skills/clickhouse-query-optimization
Command: npx skills add https://github.com/obsessiondb/clickhouse-skills --skill clickhouse-query-optimization

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

This Skill addresses slow-performing ClickHouse queries, excessive memory usage, and inefficient data retrieval, enabling users to achieve significantly faster query execution and reduced resource consumption.

Core Features & Use Cases

Query Speed Optimization: Implements over 20 rules to make queries 10-100x faster.
Memory Reduction: Helps reduce memory usage by up to 90%.
Efficient Data Access: Eliminates full table scans and optimizes JOINs.
Use Case: A user is experiencing a query that takes several minutes to return results. They can use this Skill to analyze the query, identify bottlenecks like inefficient JOINs or missing indexes, and receive actionable advice to optimize it for sub-second performance.

Quick Start

Optimize the following ClickHouse query for better performance.

Frequently Asked Questions about clickhouse-query-optimization

High-intent search queries and answers about installing and using this skill.

FAQPage Schema

How do I optimize slow ClickHouse queries and reduce memory usage?▼

To optimize slow ClickHouse queries, this Skill applies over 20 rules using PREWHERE, dictionaries, and index optimization, eliminating full table scans to achieve 10-100x faster execution and up to 90% less memory consumption.

Why does my ClickHouse query take several minutes to return results?▼

Your ClickHouse query may take minutes due to inefficient JOINs, missing indexes, or full table scans. Analyzing the query helps identify these bottlenecks and apply optimization rules for sub-second performance.

What is the best way to fix memory errors during ClickHouse data analysis?▼

The best way to fix memory errors during ClickHouse data analysis is applying optimization techniques like PREWHERE and dictionaries, which reduce memory usage by up to 90% by preventing full table scans.

Can I improve ClickHouse JOIN performance without changing my database schema?▼

Yes, you can improve ClickHouse JOIN performance by applying query optimization rules that address inefficient JOINs, leveraging dictionaries and index optimization to accelerate execution without requiring schema modifications.

When do I need to use PREWHERE for SQL performance tuning in ClickHouse?▼

You need to use PREWHERE in ClickHouse when optimizing queries to reduce memory consumption and speed up execution, as it filters data early, preventing full table scans and improving data retrieval efficiency.