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https://issues.apache.org/jira/browse/SPARK-26899?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Owen resolved SPARK-26899.
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Resolution: Not A Problem
This isn't "Major", and I don't think it's a doc problem in a comment, and I
don't think it's wrong: it's just stating what count min sketch is for in
general.
> CountMinSketchAgg ExpressionDescription is not so correct
> ---------------------------------------------------------
>
> Key: SPARK-26899
> URL: https://issues.apache.org/jira/browse/SPARK-26899
> Project: Spark
> Issue Type: Documentation
> Components: SQL
> Affects Versions: 2.4.0
> Reporter: tomzhu
> Priority: Major
>
> Hi, all, there are some not-so-correct comment in CountMinSketchAgg.scala,
> the ExpressionDescription says:
> {code:java}
> @ExpressionDescription(
> usage = """
> _FUNC_(col, eps, confidence, seed) - Returns a count-min sketch of a
> column with the given esp,
> confidence and seed. The result is an array of bytes, which can be
> deserialized to a
> `CountMinSketch` before usage. Count-min sketch is a probabilistic data
> structure used for
> cardinality estimation using sub-linear space.
> """,
> since = "2.2.0")
> {code}
> , *the Count-min sketch is a probabilistic data structure used for
> cardinality estimation*, ** actually, Count-min sketch is mainly used for
> point query, self_join size query,
> how can it support cardinality estimation? a fix might be better.
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