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From "Michael Armbrust (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (SPARK-4963) SchemaRDD.sample may return wrong results
Date Sat, 10 Jan 2015 22:20:34 GMT

     [ https://issues.apache.org/jira/browse/SPARK-4963?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Michael Armbrust resolved SPARK-4963.
-------------------------------------
       Resolution: Fixed
    Fix Version/s: 1.3.0

Issue resolved by pull request 3827
[https://github.com/apache/spark/pull/3827]

> SchemaRDD.sample may return wrong results
> -----------------------------------------
>
>                 Key: SPARK-4963
>                 URL: https://issues.apache.org/jira/browse/SPARK-4963
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 1.2.0
>            Reporter: Cheng Lian
>            Assignee: Yanbo Liang
>             Fix For: 1.3.0
>
>
> This {{sbt/sbt hive/console}} session can easily reproduce this issue:
> {code}
> sql("SELECT * FROM src WHERE key % 2 = 0").
>   sample(withReplacement = false, fraction = 0.05).
>   registerTempTable("sampled")
> println(table("sampled").queryExecution)
> val query = sql("SELECT * FROM sampled WHERE key % 2 = 1")
> println(query.queryExecution)
> // Should print `true'
> println((1 to 10).map(_ => query.collect().isEmpty).reduce(_ && _))
> {code}
> Notice that when fraction is less than 0.4, {{GapSamplingIterator}} is used to do the
sampling. My guess is that there’s something to do with the underlying mutable row objects
used in {{HiveTableScan}}, but haven't figured out the root cause.



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