Speaking of custom query languages by Big Tech companies, I've always been curious about Google's Yedalog[0]. I mean it's obviously inspired by a rich history of logic programming here, as it's trying to find a middle ground between Prolog and Datalog. I'm not sure what's come of it, and I certainly hope they eventually make it open source or at least available for BigQuery for something.

[0]: https://static.googleusercontent.com/media/research.google.c...