Cache arbitrary queries

[lorensr]

What to use as the cache key?

SQLDataSource uses the SQL query string:

https://github.com/cvburgess/SQLDataSource/blob/master/SQLCache.js#L19

Don't know if there's an equivalent for MongoDB. Cachegoose (caching for Mongoose) uses a hash of all these query properties:

https://github.com/boblauer/cachegoose/blob/master/src/extend-query.js#L70

Don't know if any of that is specific to Mongoose.

How to intercept queries?

Cachegoose monkeypatches mongoose.Query.prototype.exec:

https://github.com/boblauer/cachegoose/blob/master/src/extend-query.js#L6-L8

Ideally we would support the mongodb library as well.

Cachegoose also does aggregations, which we could do.