Apache Pinot

`FastHLL` has been deprecated for a while, the replacement for that is `DistinctCountHLL` with `BYTES` column for both performance and compaction

This is one of our clients' job. We are upgrading to Pinot 0.4. So FastHLL is not supported in 0.4?

`FastHLL` is still supported for backward-compatible, but might be removed any time. We introduced `FastHLL` as a work around because at that time we don't have `BYTES` type support.

We used to use `HllUtil` to generate star-tree for `FastHLL`. Do you use it to generate the raw data?

yes. we are not using Star tree index but just the fasthll raw data.

In that case, if it is hard to migrate to `DistinctCountHLL`, you might need to copy `HllUtil` to the client code to construct the strings

Sorry for the inconvenience, but I strongly suggest migrating to `DistinctCountHLL` which is more flexible and has better performance

thanks Jackie. For now I will try to copy `HllUtil` .