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From "Herman van Hovell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-8682) Range Join for Spark SQL
Date Mon, 14 Mar 2016 15:22:33 GMT

    [ https://issues.apache.org/jira/browse/SPARK-8682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15193470#comment-15193470
] 

Herman van Hovell commented on SPARK-8682:
------------------------------------------

I have recently updated the PR (which is a broadcast range join). It'll need a rebase though.

The thing is that this doesn't need to be in sql to work. We can use {{ExperimentalMethods.extraStrategies}}
to hook this into the planner.

> Range Join for Spark SQL
> ------------------------
>
>                 Key: SPARK-8682
>                 URL: https://issues.apache.org/jira/browse/SPARK-8682
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Herman van Hovell
>         Attachments: perf_testing.scala
>
>
> Currently Spark SQL uses a Broadcast Nested Loop join (or a filtered Cartesian Join)
when it has to execute the following range query:
> {noformat}
> SELECT A.*,
>        B.*
> FROM   tableA A
>        JOIN tableB B
>         ON A.start <= B.end
>          AND A.end > B.start
> {noformat}
> This is horribly inefficient. The performance of this query can be greatly improved,
when one of the tables can be broadcasted, by creating a range index. A range index is basically
a sorted map containing the rows of the smaller table, indexed by both the high and low keys.
using this structure the complexity of the query would go from O(N * M) to O(N * 2 * LOG(M)),
N = number of records in the larger table, M = number of records in the smaller (indexed)
table.
> I have created a pull request for this. According to the [Spark SQL: Relational Data
Processing in Spark|http://people.csail.mit.edu/matei/papers/2015/sigmod_spark_sql.pdf] paper
similar work (page 11, section 7.2) has already been done by the ADAM project (cannot locate
the code though). 
> Any comments and/or feedback are greatly appreciated.



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