I think what's becoming clear in this discussion is that there are some developers (myself definitely included) who would like to use SQL as an interface to plain programming structures outside of actual databases.

I understand postgres provides something like this, but it would be interesting as a library rather than a separate application. I'd love to be able to query hashmaps or arrays of data using SQL.

Maybe this already exists somewhere? My web-search-fu is failing me but I recall reading somewhere that facebook had something like this for querying systems, so maybe such a library exists extracted from that usecase?

Edit: Here's one. https://github.com/mozilla/moz-sql-parser