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https://issues.apache.org/jira/browse/SPARK-19122?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-19122:
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Assignee: (was: Apache Spark)
> Unnecessary shuffle+sort added if join predicates ordering differ from
> bucketing and sorting order
> --------------------------------------------------------------------------------------------------
>
> Key: SPARK-19122
> URL: https://issues.apache.org/jira/browse/SPARK-19122
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.0.2, 2.1.0
> Reporter: Tejas Patil
>
> `table1` and `table2` are sorted and bucketed on columns `j` and `k` (in
> respective order)
> This is how they are generated:
> {code}
> val df = (0 until 16).map(i => (i % 8, i * 2, i.toString)).toDF("i", "j",
> "k").coalesce(1)
> df.write.format("org.apache.spark.sql.hive.orc.OrcFileFormat").bucketBy(8,
> "j", "k").sortBy("j", "k").saveAsTable("table1")
> df.write.format("org.apache.spark.sql.hive.orc.OrcFileFormat").bucketBy(8,
> "j", "k").sortBy("j", "k").saveAsTable("table2")
> {code}
> Now, if join predicates are specified in query in *same* order as bucketing
> and sort order, there is no shuffle and sort.
> {code}
> scala> hc.sql("SELECT * FROM table1 a JOIN table2 b ON a.j=b.j AND
> a.k=b.k").explain(true)
> == Physical Plan ==
> *SortMergeJoin [j#61, k#62], [j#100, k#101], Inner
> :- *Project [i#60, j#61, k#62]
> : +- *Filter (isnotnull(k#62) && isnotnull(j#61))
> : +- *FileScan orc default.table1[i#60,j#61,k#62] Batched: false, Format:
> ORC, Location: InMemoryFileIndex[file:/table1], PartitionFilters: [],
> PushedFilters: [IsNotNull(k), IsNotNull(j)], ReadSchema:
> struct<i:int,j:int,k:string>
> +- *Project [i#99, j#100, k#101]
> +- *Filter (isnotnull(j#100) && isnotnull(k#101))
> +- *FileScan orc default.table2[i#99,j#100,k#101] Batched: false,
> Format: ORC, Location: InMemoryFileIndex[file:/table2], PartitionFilters: [],
> PushedFilters: [IsNotNull(j), IsNotNull(k)], ReadSchema:
> struct<i:int,j:int,k:string>
> {code}
> The same query with join predicates in *different* order from bucketing and
> sort order leads to extra shuffle and sort being introduced
> {code}
> scala> hc.sql("SELECT * FROM table1 a JOIN table2 b ON a.k=b.k AND a.j=b.j
> ").explain(true)
> == Physical Plan ==
> *SortMergeJoin [k#62, j#61], [k#101, j#100], Inner
> :- *Sort [k#62 ASC NULLS FIRST, j#61 ASC NULLS FIRST], false, 0
> : +- Exchange hashpartitioning(k#62, j#61, 200)
> : +- *Project [i#60, j#61, k#62]
> : +- *Filter (isnotnull(k#62) && isnotnull(j#61))
> : +- *FileScan orc default.table1[i#60,j#61,k#62] Batched: false,
> Format: ORC, Location: InMemoryFileIndex[file:/table1], PartitionFilters: [],
> PushedFilters: [IsNotNull(k), IsNotNull(j)], ReadSchema:
> struct<i:int,j:int,k:string>
> +- *Sort [k#101 ASC NULLS FIRST, j#100 ASC NULLS FIRST], false, 0
> +- Exchange hashpartitioning(k#101, j#100, 200)
> +- *Project [i#99, j#100, k#101]
> +- *Filter (isnotnull(j#100) && isnotnull(k#101))
> +- *FileScan orc default.table2[i#99,j#100,k#101] Batched: false,
> Format: ORC, Location: InMemoryFileIndex[file:/table2], PartitionFilters: [],
> PushedFilters: [IsNotNull(j), IsNotNull(k)], ReadSchema:
> struct<i:int,j:int,k:string>
> {code}
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