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https://issues.apache.org/jira/browse/SPARK-10914?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14945417#comment-14945417
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Sean Owen commented on SPARK-10914:
-----------------------------------
One long-shot question -- can you figure out whether your JVM is using
-XX:+UseCompressedOops by default? using -XX:+PrintFlagsFinal or something? it
should switch off at 32gb but is often on by default in JVMs. I hope it's not
the case that compressed OOPS throws off Tungsten.
It could also be that bigger heap sizes let tasks all execute on the same
machine and that happens to matter to reproducing this.
> Incorrect empty join sets when executor-memory >= 32g
> -----------------------------------------------------
>
> Key: SPARK-10914
> URL: https://issues.apache.org/jira/browse/SPARK-10914
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 1.5.0, 1.5.1
> Environment: Ubuntu 14.04 (spark-slave), 12.04 (master)
> Reporter: Ben Moran
>
> Using an inner join, to match together two integer columns, I generally get
> no results when there should be matches. But the results vary and depend on
> whether the dataframes are coming from SQL, JSON, or cached, as well as the
> order in which I cache things and query them.
> This minimal example reproduces it consistently for me in the spark-shell, on
> new installs of both 1.5.0 and 1.5.1 (pre-built against Hadoop 2.6 from
> http://spark.apache.org/downloads.html.)
> /* x is {"xx":1}{"xx":2} and y is just {"yy":1}{"yy:2} */
> val x = sql("select 1 xx union all select 2")
> val y = sql("select 1 yy union all select 2")
> x.join(y, $"xx" === $"yy").count() /* expect 2, get 0 */
> /* If I cache both tables it works: */
> x.cache()
> y.cache()
> x.join(y, $"xx" === $"yy").count() /* expect 2, get 2 */
> /* but this still doesn't work: */
> x.join(y, $"xx" === $"yy").filter("yy=1").count() /* expect 1, get 0 */
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