Automatic feature engineering
A typical problem: to write a Metarank config file with event to feature mapping, you need to read the docs on feature extraction and well-understand your click-through input dataset:
  • Which fields do items have? Which values does each field have?
  • Do these values look like categories?
  • How many unique values are there per field?
Nobody likes reading docs and writing YAML, so Metarank has an AutoML level-4 style generator of typical feature extractors based on the historical click-through dataset you already have.

Use the autofeature sub-command from the main binary:
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/ \_/ __ \ __\__ \\_ __ \__ \ / \| |/ /
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\/ \/ \/ \/ \/ \/ ver:None
Usage: metarank <subcommand> <options>
Subcommand: autofeature - generate reference config based on existing data
-d, --data <arg> path to a directory with input files
-f, --format <arg> input file format: json, snowplow, snowplow:tsv,
snowplow:json (optional, default=json)
-o, --offset <arg> offset: earliest, latest, ts=1663161962, last=1h
(optional, default=earliest)
--out <arg> path to an output config file
-r, --ruleset <arg> set of rules to generate config: stable, all (optional,
default=stable, values: [stable, all])
-h, --help Show help message
For all other tricks, consult the docs on https://docs.metarank.ai
An example minimal command to generate the config file for your dataset:
java -jar metarank.jar autofeature --data /path/to/events.json --out /path/to/config.yaml
For a RankLens dataset, for example, it will emit the following:
15:32:11.284 INFO a.metarank.main.command.AutoFeature$ - Generating config file
15:32:11.524 INFO ai.metarank.source.FileEventSource - path=/home/shutty/code/metarank/src/test/resources/ranklens/events/events.jsonl.gz is a file
15:32:11.537 INFO ai.metarank.source.FileEventSource - file /home/shutty/code/metarank/src/test/resources/ranklens/events/events.jsonl.gz selected=true (timeMatch=true formatMatch=true)
15:32:11.538 INFO ai.metarank.source.FileEventSource - reading file /home/shutty/code/metarank/src/test/resources/ranklens/events/events.jsonl.gz (with gzip decompressor)
15:32:15.686 INFO a.metarank.main.command.AutoFeature$ - Event model statistics collected
15:32:15.691 INFO a.m.m.c.a.r.InteractionFeatureRule$ - generated interacted_with feature for interaction 'click' over field 'writer'
15:32:15.692 INFO a.m.m.c.a.r.InteractionFeatureRule$ - generated interacted_with feature for interaction 'click' over field 'tags'
15:32:15.692 INFO a.m.m.c.a.r.InteractionFeatureRule$ - generated interacted_with feature for interaction 'click' over field 'director'
15:32:15.693 INFO a.m.m.c.a.r.InteractionFeatureRule$ - generated interacted_with feature for interaction 'click' over field 'title'
15:32:15.693 INFO a.m.m.c.a.r.InteractionFeatureRule$ - generated interacted_with feature for interaction 'click' over field 'genres'
15:32:15.693 INFO a.m.m.c.a.r.InteractionFeatureRule$ - generated interacted_with feature for interaction 'click' over field 'actors'
15:32:15.700 INFO a.m.m.c.a.r.NumericalFeatureRule$ - generated `number` feature for item field popularity in the range 0.6..967.351
15:32:15.704 INFO a.m.m.c.a.r.NumericalFeatureRule$ - generated `number` feature for item field vote_avg in the range 3.2..8.7
15:32:15.705 INFO a.m.m.c.a.r.NumericalFeatureRule$ - generated `number` feature for item field release_date in the range 3.18816E8..1.56168E9
15:32:15.707 INFO a.m.m.c.a.r.NumericalFeatureRule$ - generated `number` feature for item field budget in the range 0.0..3.8E8
15:32:15.708 INFO a.m.m.c.a.r.NumericalFeatureRule$ - generated `number` feature for item field vote_cnt in the range 15.0..30232.0
15:32:15.709 INFO a.m.m.c.a.r.NumericalFeatureRule$ - generated `number` feature for item field runtime in the range 3.0..242.0
15:32:15.719 INFO a.m.m.c.a.rules.StringFeatureRule - field writer is not looking like a categorial value, skipping
15:32:15.726 INFO a.m.m.c.a.rules.StringFeatureRule - field tags is not looking like a categorial value, skipping
15:32:15.728 INFO a.m.m.c.a.rules.StringFeatureRule - field director is not looking like a categorial value, skipping
15:32:15.730 INFO a.m.m.c.a.rules.StringFeatureRule - field title is not looking like a categorial value, skipping
15:32:15.731 INFO a.m.m.c.a.rules.StringFeatureRule - item field genres has 19 distinct values, generated 'string' feature with index encoding for top 11 items
15:32:15.734 INFO a.m.m.c.a.rules.StringFeatureRule - field actors is not looking like a categorial value, skipping
15:32:15.735 INFO a.m.m.c.a.rules.RelevancyRule$ - skipped generating relevancy feature: non_zero=0 min=Some(0.0) max=Some(0.0)
15:32:15.851 INFO ai.metarank.main.Main$ - My job is done, exiting.
Process finished with exit code 0

Metarank has multiple sets of heuristics to generate feature configuration, toggled by the --ruleset CLI option:
  • stable: a default one, ruleset with less agressive heuristics, proven to be safe in production use.
  • all: generates all features it can, even the problematic ones (like CTR, which may introduce biases).
The following stable heuristics are supported:
  • Numeric: all numerical item fields are encoded as a number feature. So for a numeric field budget describing a movie budget in dollars, it will generate the following feature extractor defitition:
- source: item.budget
type: number
name: budget
scope: item
  • String: string item fields with low-cardinality are encoded as a string feature. So movie genres field is a good candidate for this type of heuristic due to its low cardinality:
- name: genres
type: string
source: item.genres
scope: item
encode: index
values:
- drama
- comedy
- thriller
- action
- adventure
- romance
- crime
- science fiction
- fantasy
- family
- horror
  • InteractedWith: all interaction over low-cardinality fields are translated to interacted_with feature. So if a user clicked on an item with horror genre, other horror movies may get extra points:
- name: click_genres
type: interacted_with
scope: user
interaction: click
field: item.genres
  • Relevancy: if rankings with non-zero relevancy are present, then a feature relevancy is built:
- name: relevancy
type: relevancy
The all ruleset contains all stable heuristics with an addition of a couple of extra ones:
  • Rate: For all interaction types a rate feature is generated over multiple typical time windows:
- name: click_rate
type: rate
top: click
bucket: 1d
bottom: impression
scope: item
periods:
- 3
- 7
- 14
- 30
- name: count_click
type: window_count
bucket: 1d
scope: item
interaction: click
periods:
- 3
- 7
- 14
- 30

The main difference between two rulesets is the lack of rate/window_count features, which is made deliberately:
  • rate/window_count features usually introduce a popularity bias to the final ranking: as people tend to click more on popular items, ML model may attempt to always put popular items on top just because they're popular.
  • this behavior may be not that bad from the business KPI standpoint, but may make your ranking more static and less affected by past visitor actions.
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Running the autofeature generator
Supported heuristics
Why stable ruleset has no counters?