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Posted to issues@spark.apache.org by "Josh Rosen (JIRA)" <ji...@apache.org> on 2019/04/27 05:13:00 UTC
[jira] [Commented] (SPARK-27213) Unexpected results when filter is
used after distinct
[ https://issues.apache.org/jira/browse/SPARK-27213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16827449#comment-16827449 ]
Josh Rosen commented on SPARK-27213:
------------------------------------
Since this sounds like a legitimate query correctness bug, I'm adding the {{correctness}} label.
/cc [~smilegator] FYI
> Unexpected results when filter is used after distinct
> -----------------------------------------------------
>
> Key: SPARK-27213
> URL: https://issues.apache.org/jira/browse/SPARK-27213
> Project: Spark
> Issue Type: Bug
> Components: PySpark
> Affects Versions: 2.3.2, 2.4.0
> Reporter: Rinaz Belhaj
> Priority: Major
> Labels: distinct, filter
>
> The following code gives unexpected output due to the filter not getting pushed down in catalyst optimizer.
> {code:java}
> df = spark.createDataFrame([['a','123','12.3','n'],['a','123','12.3','y'],['a','123','12.4','y']],['x','y','z','y_n'])
> df.show(5)
> df.filter("y_n='y'").select('x','y','z').distinct().show()
> df.select('x','y','z').distinct().filter("y_n='y'").show()
> {code}
> {panel:title=Output}
> |x|y|z|y_n|
> |a|123|12.3|n|
> |a|123|12.3|y|
> |a|123|12.4|y|
>
> |x|y|z|
> |a|123|12.3|
> |a|123|12.4|
>
> |x|y|z|
> |a|123|12.4|
> {panel}
> Ideally, the second statement should result in an error since the column used in the filter is not present in the preceding select statement. But the catalyst optimizer is using first() on column y_n and then applying the filter.
> Even if the filter was pushed down, the result would have been accurate.
> {code:java}
> df = spark.createDataFrame([['a','123','12.3','n'],['a','123','12.3','y'],['a','123','12.4','y']],['x','y','z','y_n'])
> df.filter("y_n='y'").select('x','y','z').distinct().explain(True)
> df.select('x','y','z').distinct().filter("y_n='y'").explain(True)
> {code}
> {panel:title=Output}
>
> == Parsed Logical Plan ==
> Deduplicate [x#74, y#75, z#76|#74, y#75, z#76]
> +- AnalysisBarrier
> +- Project [x#74, y#75, z#76|#74, y#75, z#76]
> +- Filter (y_n#77 = y)
> +- LogicalRDD [x#74, y#75, z#76, y_n#77|#74, y#75, z#76, y_n#77], false
>
> == Analyzed Logical Plan ==
> x: string, y: string, z: string
> Deduplicate [x#74, y#75, z#76|#74, y#75, z#76]
> +- Project [x#74, y#75, z#76|#74, y#75, z#76]
> +- Filter (y_n#77 = y)
> +- LogicalRDD [x#74, y#75, z#76, y_n#77|#74, y#75, z#76, y_n#77], false
>
> == Optimized Logical Plan ==
> Aggregate [x#74, y#75, z#76|#74, y#75, z#76], [x#74, y#75, z#76|#74, y#75, z#76]
> +- Project [x#74, y#75, z#76|#74, y#75, z#76]
> +- Filter (isnotnull(y_n#77) && (y_n#77 = y))
> +- LogicalRDD [x#74, y#75, z#76, y_n#77|#74, y#75, z#76, y_n#77], false
>
> == Physical Plan ==
> *(2) HashAggregate(keys=[x#74, y#75, z#76|#74, y#75, z#76], functions=[], output=[x#74, y#75, z#76|#74, y#75, z#76])
> +- Exchange hashpartitioning(x#74, y#75, z#76, 10)
> +- *(1) HashAggregate(keys=[x#74, y#75, z#76|#74, y#75, z#76], functions=[], output=[x#74, y#75, z#76|#74, y#75, z#76])
> +- *(1) Project [x#74, y#75, z#76|#74, y#75, z#76]
> +- *(1) Filter (isnotnull(y_n#77) && (y_n#77 = y))
> +- Scan ExistingRDD[x#74,y#75,z#76,y_n#77|#74,y#75,z#76,y_n#77]
>
> -------------------------------------------------------------------------------------------------------------------
>
> == Parsed Logical Plan ==
> 'Filter ('y_n = y)
> +- AnalysisBarrier
> +- Deduplicate [x#74, y#75, z#76|#74, y#75, z#76]
> +- Project [x#74, y#75, z#76|#74, y#75, z#76]
> +- LogicalRDD [x#74, y#75, z#76, y_n#77|#74, y#75, z#76, y_n#77], false
>
> == Analyzed Logical Plan ==
> x: string, y: string, z: string
> Project [x#74, y#75, z#76|#74, y#75, z#76]
> +- Filter (y_n#77 = y)
> +- Deduplicate [x#74, y#75, z#76|#74, y#75, z#76]
> +- Project [x#74, y#75, z#76, y_n#77|#74, y#75, z#76, y_n#77]
> +- LogicalRDD [x#74, y#75, z#76, y_n#77|#74, y#75, z#76, y_n#77], false
>
> == Optimized Logical Plan ==
> Project [x#74, y#75, z#76|#74, y#75, z#76]
> +- Filter (isnotnull(y_n#77) && (y_n#77 = y))
> +- Aggregate [x#74, y#75, z#76|#74, y#75, z#76], [x#74, y#75, z#76, first(y_n#77, false) AS y_n#77|#74, y#75, z#76, first(y_n#77, false) AS y_n#77]
> +- LogicalRDD [x#74, y#75, z#76, y_n#77|#74, y#75, z#76, y_n#77], false
>
> == Physical Plan ==
> *(3) Project [x#74, y#75, z#76|#74, y#75, z#76]
> +- *(3) Filter (isnotnull(y_n#77) && (y_n#77 = y))
> +- SortAggregate(key=[x#74, y#75, z#76|#74, y#75, z#76], functions=[first(y_n#77, false)|#77, false)], output=[x#74, y#75, z#76, y_n#77|#74, y#75, z#76, y_n#77])
> +- *(2) Sort [x#74 ASC NULLS FIRST, y#75 ASC NULLS FIRST, z#76 ASC NULLS FIRST|#74 ASC NULLS FIRST, y#75 ASC NULLS FIRST, z#76 ASC NULLS FIRST], false, 0
> +- Exchange hashpartitioning(x#74, y#75, z#76, 10)
> +- SortAggregate(key=[x#74, y#75, z#76|#74, y#75, z#76], functions=[partial_first(y_n#77, false)|#77, false)], output=[x#74, y#75, z#76, first#95, valueSet#96|#74, y#75, z#76, first#95, valueSet#96])
> +- *(1) Sort [x#74 ASC NULLS FIRST, y#75 ASC NULLS FIRST, z#76 ASC NULLS FIRST|#74 ASC NULLS FIRST, y#75 ASC NULLS FIRST, z#76 ASC NULLS FIRST], false, 0
> +- Scan ExistingRDD[x#74,y#75,z#76,y_n#77|#74,y#75,z#76,y_n#77]
>
> {panel}
> The second query. ie *"df.select('x','y','z').distinct().filter("y_n='y'").explain(True)"* should result in error rather than giving wrong output.
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