# @cocalc/database

This package connects the hub and nextjs servers to the PostgreSQL database, and implements some nontrivial functionality to support these servers.  In particular:

- It implements changefeeds and user queries, which provides a pure JSON language similar to the basics of GraphQL for setting, getting, and subscribing to data in the database.  This uses PostgreSQL LISTEN/NOTIFY to send push notifications about changes to tables.  It's specifically designed for our data structures, of course, and is not generic.  The data structures are currently defined in `@cocalc/util/db-schema`.

## Notes

**WARNING**: This is the single scariest chunk of CoffeeScript left in CoCalc! 

**Temporary Warning:** There is a circular dependency between this package and @cocalc/server right now.  That's necessary while we rewrite the coffeescript code.  What happened was that these files `postgres-*.coffee` ended up implementing hundreds amount of "server functions"  that have nothing to do with basic database functionality.  They need to be rewritten in lots of small typescript files, mostly in `@cocalc/server`.