Load data into the online store
Feast allows users to load their feature data into an online store in order to serve the latest features to models for online prediction.
Materializing features
1. Register feature views
Before proceeding, please ensure that you have applied (registered) the feature views that should be materialized.
Deploy a feature store2.a Materialize
The materialize command allows users to materialize features over a specific historical time range into the online store.
The above command will query the batch sources for all feature views over the provided time range, and load the latest feature values into the configured online store.
It is also possible to materialize for specific feature views by using the -v / --views argument.
The materialize command is completely stateless. It requires the user to provide the time ranges that will be loaded into the online store. This command is best used from a scheduler that tracks state, like Airflow.
2.b Materialize Incremental (Alternative)
For simplicity, Feast also provides a materialize command that will only ingest new data that has arrived in the offline store. Unlike materialize, materialize-incremental will track the state of previous ingestion runs inside of the feature registry.
The example command below will load only new data that has arrived for each feature view up to the end date and time (2021-04-08T00:00:00).
The materialize-incremental command functions similarly to materialize in that it loads data over a specific time range for all feature views (or the selected feature views) into the online store.
Unlike materialize, materialize-incremental automatically determines the start time from which to load features from batch sources of each feature view. The first time materialize-incremental is executed it will set the start time to the oldest timestamp of each data source, and the end time as the one provided by the user. For each run of materialize-incremental, the end timestamp will be tracked.
Subsequent runs of materialize-incremental will then set the start time to the end time of the previous run, thus only loading new data that has arrived into the online store. Note that the end time that is tracked for each run is at the feature view level, not globally for all feature views, i.e, different feature views may have different periods that have been materialized into the online store.
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