getDiff

function

Compares the available set data to the requested data and returns the data that should be loaded from the cache and the data loaded from the base connection.

`connection.getDiff( set, availableSets )`

This attempts to find the minimal amount of data to load by going through each availableSet and doing a subset test and a set difference with set.

If set is a subset of an availableSet, {cached: set} will be returned.

If there is a difference of set and an availableSet, the difference will be what's needed. The intersection of set and that availableSet will be what's cached. A count will be taken of what's needed resulting in an object like:

{
  needed: {start: 50, end: 99},
  cached: {start: 0, end: 49},
  count: 49
}

Finally, getDiff will pick the diff objet with the lowest count. If there is no diff object, {needed: set} is returned.

Parameters

set {Set}:
The set that is being loaded.
availableSets {Array<Set>}:
An array of available sets in the cacheConnection.

Returns

{Promise<Object>}: