Chronon, Airbnb's ML Feature Platform, Is Now Open Source

Re:Chronon, Airbnb's ML Feature Platform, Is Now Open Source by mulmen on Wednesday April 10, 2024 @04:01PM (#39995117)

I’ll stop short of calling comparisons to standard SQL disingenuous but it’s definitely unrealistic because no standard SQL implementation exists.

What does this “last” operation do? There’s definitely a LAST_VALUE() window function in the databases I use. It is available in Postgres, Redshift, EMR, Oracle, MySQL, MSSQL, Bigquery, and certainly others I am not aware of.

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Re:Chronon, Airbnb's ML Feature Platform, Is Now Open Source by better365 on Thursday April 11, 2024 @01:50PM (#40004858)

That's fair.

Actually, Last is usually called last_k(n), so that you can specify the number of the values in the result array. For example, if the input column is page_view_id and n = 300, it will return the last 300 page_view_id as an array. If a window is used, for example, 7d, it will truncate the results to the past 7d. The LAST_VALUE() seems to return the last value from an ordered set. Hope that helps. Thanks for your interests.

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Re:Chronon, Airbnb's ML Feature Platform, Is Now Open Source by mulmen on Thursday April 11, 2024 @03:04PM (#40005631)

In SQL we do that with a RANK window function then apply a filter to that rank. It can also be done with a correlated subquery.

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