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Posted to issues@flink.apache.org by "Josh Mahonin (Jira)" <ji...@apache.org> on 2022/07/28 15:53:00 UTC

[jira] [Created] (FLINK-28736) Add APPROX_PERCENTILE function

Josh Mahonin created FLINK-28736:
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             Summary: Add APPROX_PERCENTILE function
                 Key: FLINK-28736
                 URL: https://issues.apache.org/jira/browse/FLINK-28736
             Project: Flink
          Issue Type: Improvement
    Affects Versions: 1.15.1
            Reporter: Josh Mahonin


We have an {{APPROX_PERCENTILE}} UDF that we believe may be useful to the broader community. It's a rather simple implementation that wraps TDigest to return approximate quantile/percentile data in both batch and streaming mode.

I'm somewhat torn as to how to properly contribute this. Following Calcite conventions, I believe this would qualify as an {{APPROXIMATE PERCENTILE_DISC}} function, although that would require Calcite >= 1.28 (FLINK-21239, FLINK-27998). 

Alternatively, perhaps this could simply be dropped in as a new function that's not backed by Calcite, although it's not immediately clear to me how to proceed with that, though I'm happy to take guidance here.

This is a gist of the implementation:
https://gist.github.com/jmahonin/d75150999af30bc78bdf00c7b0ecbd4f



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