allow $select in params query when get

[beeplin]

The service method get allows a params to be passed in, but currently just ignores it, as @daffl explained in here:

By default get just returns a record by its id, adding a query wouldn't really change anything about that.

But in fact $select in the query does change something. It would pluck the record and only returns the fields you need. This is particularly useful when you have a client-side cache of the record and want to see if the record is expired: you can just do:

service.get(id, {query: {$select: ['updatedAt']}}
.then (data) => {
  // check if data.updatedAt is newer than the local updatedAt 
} 

By doing this we could just transfer a small part of the record (only the id and the updatedAt time), and then be able to check if the cache is expired. If does, call get again to get the whole record; if not, just use the cache.

But currently, when calling get for the first time, it always return the whole record (might be very very large), making the client-side cache totally useless.

[daffl]

Indeed. There is several issues for this (feathersjs-ecosystem/feathers-service-tests#25 being the starting point). The current workaround for this is a three line hook:

const pick = require('lodash.pick');

app.service('myservice').after(function(hook) {
  if(hook.params.query.$select) {
    hook.result = pick(hook.result, hook.params.query.$select);
  }  
});

[beeplin]

hmmm.. does lodash.pick support dot notation of fields?

I would go with this workaround for now, but to be frankly it's painful to add this hook to all services in an app. I understand that making this change to get is a huge work since all database adapters must be modified and tested. I am wondering if there are any schedules for this?

[daffl]

This will be released for all adapters shortly. But I just wanted to point out that it is now pretty easy to add a hook to all services with application hooks in feathers-hook v1.6.0.

[beeplin]

cool~!

[daffl]

This has now been merged and released as a minor version in all official adapters.

[lock]

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