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Posted to issues@spark.apache.org by "Hyukjin Kwon (Jira)" <ji...@apache.org> on 2020/02/17 04:26:00 UTC

[jira] [Created] (SPARK-30847) Take productPrefix into account in MurmurHash3.productHash

Hyukjin Kwon created SPARK-30847:
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             Summary: Take productPrefix into account in MurmurHash3.productHash
                 Key: SPARK-30847
                 URL: https://issues.apache.org/jira/browse/SPARK-30847
             Project: Spark
          Issue Type: Bug
          Components: SQL
    Affects Versions: 2.4.5, 3.0.0
            Reporter: Hyukjin Kwon


Potentially a correctness issue. See the issue in https://github.com/scala/bug/issues/10495 and fix https://github.com/scala/scala/pull/7648.

Currently, different expressions with same children can produce the same hash as below:

{code}
scala> spark.range(1).selectExpr("id - 1").queryExecution.analyzed.semanticHash()
res0: Int = -565572825

scala> spark.range(1).selectExpr("id + 1").queryExecution.analyzed.semanticHash()
res1: Int = -565572825
{code}

The reason seems to be it doesn't take the product's class itself



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