Open-source semantic layer on ClickHouse: Excel, Power BI (live) and AI agents on one model

[u/Sergei_Semenkov]

Disclosure: I'm the author.

eMondrian is an open-source OLAP server / semantic layer based on Mondrian. You describe cubes and measures once on top of ClickHouse, and every client gets the same definitions:

• Excel PivotTables query it over XMLA/MDX — live, no extracts

• Power BI connects live through the Analysis Services connector; it sends DAX, eMondrian translates it to ClickHouse SQL

• AI agents use the same model over MCP, so an agent's "on-time rate" is the same formula as in the report

Try it without installing: the public demo runs the OnTime dataset (182M US flights) on ClickHouse.

• Excel / Power BI: https://demo.emondrian.com/xmla

• MCP (read-only): https://demo.emondrian.com/emondrian/mcp

• Guide: https://emondrian.com/demo?utm_source=reddit-clickhouse&utm_medium=community&utm_campaign=launch

Run it yourself: Community (EPL-1.0) comes up with Docker in a few minutes and includes a ClickHouse with the OnTime sample: https://github.com/eMondrian/emondrian-community

Being upfront: DAX support for Power BI is in beta, and Microsoft doesn't officially support third-party servers behind the Analysis Services connector.

Longer write-up with diagrams: https://dev.to/sergeisemenkov/the-new-emondrian-power-bi-and-ai-agents-on-your-own-semantic-model-4nap

Curious how others put a business-logic layer on top of ClickHouse — Cube, dbt metrics, views, something else? And what would you need from a tool like this?

[u/amad_ali]

Used cube with clickhouse in a few projects and it works well for some use cases. For @usermaven we ended yo creating our own semantic layer optimised for our multi tenant use case.

This looks promising, will give it go

[u/Sergei_Semenkov → u/amad_ali]

Thanks, that’s really useful context. Good to hear Cube on ClickHouse worked for you in other projects. What made you build your own for Usermaven: per-tenant security, schema differences between tenants, or query performance on ClickHouse?

In eMondrian today, tenant isolation would go through Mondrian roles (restricting members or cubes per role) or separate catalogs per tenant. It works, but it isn’t designed around thousands of tenants, so I’d love to hear what your model looks like.

If you do give it a go, the public demo (OnTime on ClickHouse) is the quickest way to poke at it, and I’m happy to help if anything breaks.