Derived feature (like "join")

Raptor is introducing a new way to join between pieces of data - "dependencies".

As explained earlier, we write features as functions and working in the context of a "row-level" approach.

To implement a feature that "joins" a data from two different sources, we just need to call another feature that calculates the data we need.

Quick example

A relatively simple example for this is the following "rate" feature:

@feature(keys=["user_id"], sourceless_markers_df=markers_df)  # sourceless_markers_df is used for training
@freshness(max_age='1m', max_stale='10h')
def views_purchases_rate(_, ctx: Context) -> float:
  """rate of two views and purchases"""
  views, _ = ctx.get_feature("views+count")
  purchases, _ = ctx.get_feature("purchases+count")
  return views / purchases

In this code, we're using the feature_get() function to request the values of views+count and purchases+count for our user_id key(by default, the function propagate the keys). Then, we return the rate of the two. Simple right?

Using with sourceless features