spotify/scio

Reservoir sampling into a side output?

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#1,321 opened on Aug 23, 2018

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 (6 comments) (0 reactions) (0 assignees)Scala (529 forks)auto 404
enhancementgood first issue

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Description

Right now we have SCollection#sample which uses a Beam transform and is implemented as a global combine operation. It'll be nice to have a sample into side output variation that passes main input through while randomly reservoir sample them into a side input. We should also benchmark this approach against the Beam implementation.

Contributor guide

Research direction
Study the current SCollection#sample implementation, understand Beam's side output concept (e.g., with ParDo and PCollectionViews), implement a new method that passes the main input unchanged while reservoir sampling a random subset into a side output. Benchmark the new approach against the global combine implementation.
Tech stack
scala
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Scala
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70