[blixtra]

The project looks very interesting. But I had a look at the license of the Citus source code and it appears to be under an AGPL license and I didn't see an exception for the part of the code that you're including in Hydra. FWIU, AGPL code is not compatible with including in Apache code, although the opposite is compatible. So, I'd be interested to know if I'm understanding this wrong or if there is some license exception I'm not seeing.

[blixtra]

I'll answer my own question after doing some more digging. It seems that as the columnar code is a self-contained PostgreSQL extension, you're only using the API which would be fine as there is no linking involved.