ClickHouse 26.1 New Features Lab

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A hands-on laboratory for learning and testing ClickHouse 26.1 new features. This directory focuses on verified and working features newly added in ClickHouse 26.1 (released 2026-01-29, the first release of 2026).

📋 Overview

ClickHouse 26.1 includes significant enhancements in data management, text search capabilities, keeper operations, and performance optimizations. This release features new functions, expanded data type support, and improved query execution strategies.

🎯 Key Features

1. reverseBySeparator Function - New string function for flexible text manipulation
2. Text Index for Array Columns - Full-text search capabilities extended to arrays
3. HTTP API for ClickHouse Keeper - Built-in web UI and REST API for keeper monitoring
4. DeltaLake Deletion Vectors - Efficient row-level deletion support for data lakes

🚀 Quick Start

Prerequisites

• macOS (with Docker Desktop)
• oss-docker environment setup

Setup and Run

# 1. Install and start ClickHouse 26.1
cd local/releases/26.1
./00-setup.sh

# 2. Run tests for each feature
./01-reverse-by-separator.sh
./02-text-index-arrays.sh
./03-keeper-http-api.sh

Manual Execution (SQL only)

To execute SQL files directly:

# Connect to ClickHouse client
cd ../../oss-docker
./client.sh 8123

# Execute SQL file
cd ../local/releases/26.1
source 01-reverse-by-separator.sql

📚 Feature Details

1. reverseBySeparator Function (01-reverse-by-separator)

New Feature: Function that reverses the order of substrings in a string separated by a specified separator

Test Content: - Basic string reversal with various separators - Path manipulation (URL paths, file paths) - Domain name reversing (e.g., com.example.www) - CSV column reordering - Breadcrumb navigation reversal - Log format transformation

Execute:

./01-reverse-by-separator.sh
# Or
cat 01-reverse-by-separator.sql | docker exec -i clickhouse-26-1 clickhouse-client --multiline --multiquery

Key Learning Points: - reverseBySeparator(separator, string) reverses substring order - Useful for path normalization and format conversion - Works with any string separator (/, ., -, etc.) - Preserves empty segments in the string - Can be combined with other string functions - Efficient for URL and path manipulation

Use Cases: - URL path manipulation and normalization - Reverse domain name lookups (PTR records) - File path transformations - Log format conversions - Breadcrumb navigation building - CSV/TSV column reordering - Namespace and package name handling - Hierarchical data restructuring

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2. Text Index for Array Columns (02-text-index-arrays)

New Feature: Text indexing capabilities extended to support Array data types for full-text search

Test Content: - Creating text indexes on Array(String) columns - Multi-keyword search in arrays - Tag and category search optimization - Product feature search - Comment and review text search - Performance comparison with and without indexes

Execute:

./02-text-index-arrays.sh

Key Learning Points: - Text indexes now work on Array(String) columns - Significantly improves search performance on array data - Uses same syntax as regular text indexes - Supports various tokenizers (ngrams, tokens, etc.) - Can index tags, categories, and multi-value fields - Reduces query latency for array searches

Use Cases: - Product tag and category search - Multi-keyword article search - E-commerce filter optimization - Social media hashtag search - Document keyword indexing - User interest and preference search - Skills and capabilities matching - Content recommendation systems

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3. HTTP API for ClickHouse Keeper (03-keeper-http-api)

New Feature: Built-in HTTP API and embedded web interface for ClickHouse Keeper monitoring and management

Test Content: - Accessing Keeper status via HTTP API - Querying cluster configuration - Monitoring keeper metrics - Inspecting znode data - Health check endpoints - Web UI exploration

Execute:

./03-keeper-http-api.sh

Key Learning Points: - Keeper now includes built-in HTTP API - Web UI available at keeper's HTTP port - REST endpoints for status, config, and metrics - No external tools required for monitoring - JSON responses for easy integration - Simplifies keeper operations and debugging

Use Cases: - Keeper health monitoring - Cluster configuration inspection - Operational dashboards - Automated health checks - Integration with monitoring tools (Prometheus, Grafana) - Troubleshooting keeper issues - Znode data inspection - Cluster status visualization

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🔧 Management

ClickHouse Connection Info

• Web UI: http://localhost:8123/play
• HTTP API: http://localhost:8123
• TCP: localhost:9000
• User: default (no password)

Useful Commands

# Check ClickHouse status
cd ../../oss-docker
./status.sh

# Connect to CLI
./client.sh 8123

# View logs
docker logs clickhouse-26-1

# Stop
./stop.sh

# Complete removal
./stop.sh --cleanup

📂 File Structure

26.1/
├── README.md                        # This document
├── 00-setup.sh                      # ClickHouse 26.1 installation script
├── 01-reverse-by-separator.sh       # reverseBySeparator function test
├── 01-reverse-by-separator.sql      # reverseBySeparator SQL
├── 02-text-index-arrays.sh          # Text index for arrays test
├── 02-text-index-arrays.sql         # Text index for arrays SQL
├── 03-keeper-http-api.sh            # Keeper HTTP API test
└── 03-keeper-http-api.sql           # Keeper HTTP API SQL

🎓 Learning Path

For Beginners

1. 00-setup.sh - Understand environment setup
2. 01-reverse-by-separator - Learn new string manipulation functions
3. 02-text-index-arrays - Introduction to full-text search on arrays

For Intermediate Users

1. 03-keeper-http-api - Explore keeper management and monitoring
2. Build search features with text indexes on arrays
3. Integrate string functions into data processing pipelines

For Advanced Users

• Apply text indexes to production array columns
• Build keeper monitoring dashboards
• Performance optimization with new features
• Integrate keeper API with external monitoring systems

🔍 Additional Resources

• Release Presentation: ClickHouse 26.1 Community Call
• ClickHouse Documentation: docs.clickhouse.com
• Release Notes: Changelog 2026
• Newsletter: January 2026 Newsletter

📝 Notes

• Each script can be executed independently
• Read and modify SQL files directly to experiment
• Test data is generated within each SQL file
• Cleanup is commented out by default for inspection
• All features verified on ClickHouse 26.1.12.23

🆕 What's New in 26.1

• New String Functions including reverseBySeparator for flexible text manipulation
• Text Index Enhancements with Array column support
• Keeper Improvements with built-in HTTP API and web UI
• Performance Optimizations including skip indexes on data read (default enabled)
• DeltaLake Support with deletion vectors for efficient row-level operations
• Enhanced Type System with Variant type as default common type
• Query Optimizations with improved JOIN filter pushdown and window functions

🤝 Contributing

If you have improvements or additional examples for this lab: 1. Register an issue 2. Submit a Pull Request 3. Share feedback

📄 License

MIT — free to learn from and modify.

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Happy Learning! 🚀

For questions or issues, please refer to the main clickhouse-hols README.

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# 1. ClickHouse 26.1 설치 및 시작
cd local/releases/26.1
./00-setup.sh

# 2. 각 기능별 테스트 실행
./01-reverse-by-separator.sh
./02-text-index-arrays.sh
./03-keeper-http-api.sh

# ClickHouse 클라이언트 접속
cd ../../oss-docker
./client.sh 8123

# SQL 파일 실행
cd ../local/releases/26.1
source 01-reverse-by-separator.sql

./01-reverse-by-separator.sh
# 또는
cat 01-reverse-by-separator.sql | docker exec -i clickhouse-26-1 clickhouse-client --multiline --multiquery

./02-text-index-arrays.sh

./03-keeper-http-api.sh

# ClickHouse 상태 확인
cd ../../oss-docker
./status.sh

# CLI 접속
./client.sh 8123

# 로그 확인
docker logs clickhouse-26-1

# 중지
./stop.sh

# 완전 삭제
./stop.sh --cleanup

26.1/
├── README.md                        # 이 문서
├── 00-setup.sh                      # ClickHouse 26.1 설치 스크립트
├── 01-reverse-by-separator.sh       # reverseBySeparator 함수 테스트
├── 01-reverse-by-separator.sql      # reverseBySeparator SQL
├── 02-text-index-arrays.sh          # 배열 텍스트 인덱스 테스트
├── 02-text-index-arrays.sql         # 배열 텍스트 인덱스 SQL
├── 03-keeper-http-api.sh            # Keeper HTTP API 테스트
└── 03-keeper-http-api.sql           # Keeper HTTP API SQL