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Posted to issues@spark.apache.org by "Apache Spark (JIRA)" <ji...@apache.org> on 2016/07/04 18:11:11 UTC
[jira] [Assigned] (SPARK-16355) Incorrect Statistics when Queries
Containing LIMIT/TABLESAMPLE 0
[ https://issues.apache.org/jira/browse/SPARK-16355?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Apache Spark reassigned SPARK-16355:
------------------------------------
Assignee: (was: Apache Spark)
> Incorrect Statistics when Queries Containing LIMIT/TABLESAMPLE 0
> ----------------------------------------------------------------
>
> Key: SPARK-16355
> URL: https://issues.apache.org/jira/browse/SPARK-16355
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.0.0
> Reporter: Xiao Li
>
> When a query containing LIMIT/TABLESAMPLE 0, the statistics could be zero. Results are correct but it could cause a huge performance regression. For example,
> {noformat}
> Seq(("one", 1), ("two", 2), ("three", 3), ("four", 4)).toDF("k", "v")
> .createOrReplaceTempView("test")
> val df1 = spark.table("test")
> val df2 = spark.table("test").limit(0)
> val df = df1.join(df2, Seq("k"), "left")
> {noformat}
> The statistics of both {{df}} and {{df2}} are zero. The statistics values should never be zero; otherwise `sizeInBytes` of `BinaryNode` will also be zero (product of children).
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