This is nice because there are a lot of clickhouse fdw implementations and none of them are well maintained from what I can tell.
Appreciate you chiming in! We evaluated almost all the FDWs and landed on clickhouse_fdw (built by Ildus) as the most mature option. However, it hadn’t been maintained since 2020. We used it as the base, and the goal is to take it to the next level.
Our main focus is comprehensive pushdown capabilities. It was very surprising to see how much the Postgres FDW framework has evolved over the years and the number and types of hooks it now provides for push down. This is why we decided to lean into FDW than build an extension bottoms up. But we may still do that within pg_clickhouse for a few features, wherever FDW framework becomes a restriction.
We’ve made notable progress over the last few months, including support for pushdown of custom aggregations and SEMI JOINs/basic subqueries. Fourteen of twenty-two TPCH queries are now fully pushdownable.
We’ll be doubling down to add pushdown support for much more complex queries, CTEs, window functions, and more. More on the future here - https://github.com/ClickHouse/pg_clickhouse?tab=readme-ov-fi... All with the goal of enabling users to build fast analytics from the Postgres layer itself but still using the power of ClickHouse!
>All with the goal of enabling users to build fast analytics from the Postgres layer itself but still using the power of ClickHouse!
That would be incredible! So many times I want to reach for ClickHouse but whatever company I'm at has so much inertia built into PG. Pleease add CTE support.
And yes I'm aware of PeerDB or whatever that project is called. This is still or even more helpful.
You're replying to the CEO of PeerDB. We recognize CDC is only one tool in the integration toolbox, which is why we're prioritizing this
At this stage it may be possible to build one's entire application stack inside of postgres extensions.
This is pretty good. It will allow us to use PostgREST as an API endpoint to query the ClickHouse database directly
Good idea! Btw, ClickHouse does provide a HTTP interface directly, too! https://clickhouse.com/docs/interfaces/http
Ooh, neat idea!
What are the typical uses of PostgREST? is it just when you want to make your database accessible to various languages over HTTP because you don't want to use an ORM and connect to your db? But besides that, for an entreprise solution, why would you use PostgREST to develop your backend rather than, say, use an ORM in your language and make direct queries? (honest question)
You skip the backend entirely and query from the frontend. PostgREST and Postgres is your backend. If you want extra sauce on top you route those paths to an application that does whatever extra imperative operations you need.
This always sounds super messy to me but I guess supabase is kind of the same thing and especially for side projects it seems like a very efficient setup.
So a kind of "mini-Firebase" ? and then you have security through row-based security?
But this also means your users can generate their own queries, possibly doing some weird stuff taking down the db, so I assume it's more for "internal tools"?
Yeah definitely not for public facing things of any capacity.
No matter your size unless you have a trivial amount of data, if you expose a full SQL query language you can be hit be a DOS attack pretty trivially.
This ignores that row level security is also not enough on its own to implement an even moderately capable level of access controls.
I'm using Postgres as my base business database, and thinking now about linking it to either DuckDb/DuckLake or Clickhouse...
what would you recommend and why?
I understand part of the interest of pg_clickhouse is to be able to use "pre-existing Postgres queries" on an analytical database without having to change anything, so if I am building my database now and have no legacy, would pg_clickhouse make sense, or should I do analytics differently?
Also, would you have some kind of tutorial / sample setup of a typical business application in Postgres and kind of replication in clickhouse to make analytics queries? so I can see how Clickhouse would be typically used?
Depending on your workload you might also be able to use Timescale to have very fast analytical queries inside postgres directly. That avoids having to replicate the data altogether.
Note that I work for the company that built timescale (Tiger Data). Clickhouse is cool though, just throwing another option into the ring.
Tbf in terms of speed Clickhouse pulls ahead on most benchmark, unless you want to join a lot with your postgres data directly then you might benefit from having everything in one place. And of course you avoid the sync overhead.
I'm indeed already using Timescaledb, I was wondering if I would really gain something from adding clickhouse
I was using Timescale for a small project of mine and eventually switched to Clickhouse. While there was a 2-4x disk space reduction, the major benefits have operational (updates & backups). The documentation is much better since Timescale's mixes their cloud product documentation in, really muddying the water.
Despite that, man it is really nice to be able to join your non-timeseries data in your queries (perhaps the fdw will allow this for clickhouse? I need to look into that). If you don't have to deal with the operations side too much and performance isn't a problem, Timescale is really nice.
More on use-cases involving TimescaleDB replication/migration to ClickHouse https://clickhouse.com/blog/timescale-to-clickhouse-clickpip...
We released a meltano target for DuckLake[0]. dlt has one now too. Pretty easy to sync pg -> ducklake.
I've been really happy with DuckLake, happy to answer any questions about it.
DuckDB has always felt easier to use vs. Clickhouse for me, but both are great options. If I were you, I'd try both options for a few hours with your use case and pick the one that feels better.
I love DuckDB from a product perspective and appreciate the engineering excellence behind it. However, DuckDB was primarily built for seamless for in-process analytics, data science, data-preparation/ETL workloads than real-time customer facing analytics.
ClickHouse’s bread and butter is real-time analytics for customer-facing applications, which often come with demanding concurrency and latency requirements.
Ack, totally makes sense that both are amazing technologies - you could try both and test them at the scale your real-time application may reach, and then choose the technology that best fits your needs. :)
I tested DuckDB and even Motherduck and this was my takeaway. Square hole, round peg situation.
Nice, what would be your typical setup?
You keep like 1 year's worth of data in your "business database", and then archive the rest in S3 with parquet and query with DuckDB ?
And if you want to sync everything, even "current data", to do datascience/analytics, can you just write the recent data (eg the last week of data or whatever) in S3 every hours/days to get relatively up-to-date data? And doesn't that cause the S3 data to grow needlessly (eg does it replace, rather than store an additional copy of recent data each hour?)
Do you have kind of "starter project" for a Postgres + DuckLake integration that I could look at to see how it's used in practice, and how it makes some operations easier?
Once you have meltano installed, it's just be:
```
meltano run tap-postgres target-ducklake
```
0 - https://www.notion.so/luabase/Postgres-to-DuckLake-example-2...
Great question! If you’re starting a greenfield application, pg_clickhouse makes a lot of sense since you’ll be using a unified query layer for your application.
Now, coming to your question about replication: you can use PeerDB (acquired by ClickHouse https://github.com/PeerDB-io/peerdb), which is laser-focused and battle-tested at scale for Postgres-to-ClickHouse replication. Once the data is replicated into ClickHouse, you can start querying those tables from within Postgres using pg_clickhouse. In ClickHouse Cloud, we offer ClickPipes for Postgres CDC/replication, which is a managed service version of PeerDB and is tightly integrated with ClickHouse. Now there could be non-transcational tables that you can directly ingest to ClickHouse and still query using pg_clickhouse.
So TL;DR: Postgres for OLTP; ClickHouse for OLAP; PeerDB/ClickPipes for data replication; pg_clickhouse as the unified query layer. We are actively working on making this entire stack tightly integrated so that building real-time apps becomes seamless. More on that soon! :)
The name of the project is a reference to P. G. Wodehouse[0] for those unaware.
Hmm, no.
It’s just like all the other postgres extensions named “pg_foo”, and the clear and obvious choice for “foo” in this case is “clickhouse”.
Unless this is some bad joke that has flown over my head.
I will never un-see it now, tbh
"I am never wrong, sir" -onedognight
LOL