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Hello and welcome to another ClickHouse newsletter!
We’ve got another feature-packed ClickHouse release, with custom HTTP handlers, pipelined SQL, and Japanese/Chinese tokenizers for the text-index.
Elsewhere, Mohamed Hussain S dives into the replication queue, Tom Schreiber and Lionel Palacin share the first end-to-end results from CostBench, and Himanshu Pandey walks us through reading ClickHouse query plans.
We also have preview releases of PromQL, On-Demand Compute, AI functions, and sub-second Postgres replication to ClickHouse
Featured community member: Rory Shanks
This month's featured community member is Rory Shanks, ClickHouse Engineer at PostHog.
Rory’s background is in site reliability and cloud platform engineering, and he previously worked as a Staff DevOps Engineer at ENWAY and a Senior Site Reliability Engineer at Inkitt and powercloud.
Rory contributed several improvements to ClickHouse 26.8, released at the end of August.
First, he added an option for replicas to fetch already mutated data parts from another replica, avoiding the need to repeat mutation work locally. Additionally, he added caching for tokens absent from the text index and improved JSON subcolumn reads by reusing column metadata during conversions.
➡️ Connect with Rory on LinkedIn
Open House Roadshow
We’re halfway through the Open House Roadshow, but there are still visits to come in Bangalore (Sep 22), London (Sep 30), and Munich (Oct 6), so don’t forget to sign up!
➡️ See all Open House locations
26.8 release
After last month’s mega 26.7 release blog post, we’ve decided to try something different this month: multiple smaller posts!
The 26.8 release includes a series of features, such as custom HTTP handlers and dynamic query filtering, that enable you to use ClickHouse as a streaming HTTP API. This release also adds a new |> operator that lets us write queries as a sequence of transformations.
The release also adds a system.user_query_log table that shows only the current user’s queries, a URL database engine, and Japanese and Chinese tokenizer support for the text index.
Understanding the replication queue in ClickHouse
Mohamed Hussain S explores ClickHouse’s replication queue by stopping a replica and investigating the backlog.
He shows how to use the system.replicas and system.replication_queue system tables to diagnose issues, and explains why a non-empty queue doesn’t necessarily mean something is wrong.
Measuring real-time performance per dollar under continuous load: CostBench’s first end-to-end results
Tom Schreiber and Lionel Palacin share the first end-to-end results from CostBench, an open benchmark for cloud data warehouse cost-performance: performance-per-dollar, rather than just speed.
They test ClickHouse Cloud, Snowflake, BigQuery, and Redshift Serverless under continuous ingestion, measuring the cost of keeping fresh data ready for queries alongside query performance.
In a follow-up post, they take a closer look at the ClickHouse Cloud and Snowflake results, explaining how their architectures and billing models contribute to the performance-per-dollar gap.
Announcing On-Demand Compute: Instant compute for your most intensive workloads
This is one of the biggest features we have been working on: On-Demand Compute is now in private preview.
You are now a step away from offloading intensive workloads to dedicated ClickHouse workers. And it doesn’t land alone! It comes with two friends:
• A new cost-based optimizer (CBO)
• A new distributed query execution framework
The dream for anybody wanting to offload ad-hoc or data lake queries to dedicated workers!
Curious to learn more? Melvyn Peignon will present a live webinar on September 24th, where he’ll explain how it works, give a live demo, and talk through the six-month roadmap.
ClickHouse 26.8 LTS: 57 Breaking Changes Since 26.3
Mohamed Hussain S has written an alternative blog post for the 26.8 release, exploring changes since the previous LTS release, 26.3.
He highlights breaking changes and new defaults across all five releases, with a checklist of what to audit before upgrading and monitor afterward.
Postgres Round-up
We’ve been publishing more and more Postgres content as the weeks go by, so I thought it deserved its own section in the newsletter.
- Sai Srirampur announced WalShadow, an open-source engine that replicates Postgres data to ClickHouse directly from the physical WAL. It’s available as an open-source project or in private preview on ClickHouse Managed Postgres.
- Kunal Gupta announced the availability of ClickHouse Managed Postgres on Google Cloud, also in private preview for the time being.
- David Wheeler announced the open-source chdb Postgres extension, which expands Postgres import and export features via the chDB library.
- Gülçin Yıldırım Jelínek has started writing a series of blog posts on Postgres 19. So far, she’s covered monitoring, new system views, and read-your-writes.
- Kaushik Iska explains how ClickHouse Managed Postgres protects Postgres from resource-hungry supporting processes.
- Sai Srirampur explores how storage choices affect Postgres performance.
- Cristina Albu and Yashpreet Bathla walk through a new onboarding flow for ClickHouse Managed Postgres.
Introducing ClickHouse's new TimeSeries Engine: Your drop-In Prometheus replacement
James Cunningham introduces PromQL and the TimeSeries table engine in ClickHouse Cloud, now in private preview.
You can send metrics to ClickHouse through Prometheus remote write and query them with PromQL in Grafana, ClickHouse, or ClickStack, all while keeping your existing collection setup.
Quick reads
- Saarth Soni compares streaming and batch counts of Wikipedia edits using Quix Streams and ClickHouse, exploring why the same data can yield different results.
- Oleksandr Andrushchenko compares ClickHouse and PostgreSQL for SMS analytics, reporting that ClickHouse processes 10 times more rows and exploring how query shape affects performance.
- Himanshu Pandey explains how to read ClickHouse query plans to understand query execution and investigate performance.
- Andriy Yakovlev and George Larionov introduce AI Functions in ClickHouse, bringing AI models into SQL for tasks such as text generation, classification, and embeddings.
- Pete Hampton shows how to build semantic search with Google’s MCP Toolbox and ClickHouse, automatically turning text into embeddings for storage and search.
- Lareb Zafar introduces ClickGap, an autonomous QA agent that tests merged ClickHouse changes and traces regressions to the commits that introduced them.
Upcoming events
Global virtual events
- Webinar: What if your most intensive queries could run on more compute? Introducing On-Demand Compute - Sep 24, 2026 (AMER)
- Webinar: What if your most intensive queries could run on more compute? Introducing On-Demand Compute - Oct 7, 2026 (EMEA)
Virtual training
- Query Optimization with ClickHouse Workshop - Sep 29, 2026
- PostgreSQL and ClickHouse, Better Together - - Oct 8, 2026
- Real-time Analytics with ClickHouse: Level 1 - Oct 20, 2026
- Real-time Analytics with ClickHouse: Level 2 - Oct 21, 2026
- Real-time Analytics with ClickHouse: Level 3 - Oct 22, 2026
Events in AMER
- Rows and Columns summit San Francisco - Sep 22nd
- Google Cloud Summit Brasil - Sep 23-24, 2026
- Runway by RunReveal - San Francisco - Sep 29, 2026
- CoreWeave Fully Connected - San Francisco - Sep 29 - Oct 2, 2026
- Sao Paulo In-person training - Observabilidade com ClickStack - Sao Paulo - Oct 8, 2026
- Sao Paulo Meetup - Observabilidade de Agentes em Escala: o Case do iFood com Langfuse - Sao Paulo - Oct 8, 2026
Events in EMEA
- AI Engineer Paris (Langfuse) - Sept 22-24, 2026
- Stockholm In-Person Training: Real-time Analytics with ClickHouse - Sep 23, 2026
- AI Builders and Databases Barcelona - Sep 23, 2026
- BigDataLondon - Sept 23-24, 2026
- Copenhagen In-person training - Sept 24, 2026
- FabCON - Sept 28 - Oct 1
- FabCon Lunch and Learn - Sept 30, 2026
- AI Builders and Databases Paris - Sep 29, 2026
- Agentic AI Forum Dubai - Sept 30, 2026
- London In-person training - From 0 to Production: Observing and Improving AI Agents with Langfuse - Sep 30, 2026
- London In-person training - One Database, Every Workload: A ClickHouse Workshop - Sep 30, 2026
- Open House Roadshow London - Sep 30, 2026
- Munich In-person training - From 0 to Production: Observing and Improving AI Agents with Langfuse - Oct 6, 2026
- Munich In-person training - One Database, Every Workload: A ClickHouse Workshop - Oct 6, 2026
- Open House Roadshow Munich - Oct 6, 2026
- World Summit AI Amsterdam - Oct 7-8, 2026
- AI Builders and Databases Stockholm - Oct 8, 2026
- AI Builders and Databases Tel Aviv - Oct 12, 2026
- SRECon Dublin Happy Hour by the Quay - Oct 13, 2026
- SRECon Dublin - Oct 13-15, 2026
- Data Innovation Summit Dubai Oct 14-15
- Oslo In-Person Training: Real-time Analytics with ClickHouse - Oct 14, 2026
- PostgreSQL Conference Europe - Oct 20-23, 2026
- AWS Cloud Days Riyadh - Oct 21, 2026
- London In-Person Training: Real-time Analytics with ClickHouse - Oct 21, 2026
- AI Builders and Analytics London - Oct 21, 2026
- AI Builders and Databases Dubai - Oct 22, 2026
- Battle of the Quants London - Oct 22, 2026
- Dublin In-Person Training: Real-time Analytics with ClickHouse - Oct 23, 2026
- AI Builders and Databases Madrid - Nov 3, 2026
- AI Builders and Databases Cyprus - Limassol - Nov 26, 2026
Events in APAC
- Open House Roadshow Bangalore - Sep 22, 2026
- Singapore - From 0 to Production: Observing and Improving AI Agents with Langfuse - Sep 24, 2026
- Singapore: One Database, Every Workload: A ClickHouse Workshop - Sep 24, 2026
- Singapore: Build Better LLM Apps - Sep 29, 2026
- Auckland: One Database, Every Workload: A ClickHouse Workshop - Oct 6, 2026
- Auckland: Build a unified data stack with Postgres and ClickHouse - Oct 6, 2026
- Singapore: Confluent Financial Services Leaders Summit - Oct 9, 2026
- Sydney: Build a unified data stack for real-time AI with Postgres and ClickHouse - Oct 13, 2026
- Melbourne: Build Better LLM Apps - Oct 15, 2026
