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https://issues.apache.org/jira/browse/SPARK-19609?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16947001#comment-16947001
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Nick Dimiduk commented on SPARK-19609:
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Hi [~hyukjin.kwon], mind adding a comment as to why this issue was closed? Has
the functionality been implemented elsewhere? How about a link off to the
relevant JIRA so I know what fix version to look for? Thanks!
> Broadcast joins should pushdown join constraints as Filter to the larger
> relation
> ---------------------------------------------------------------------------------
>
> Key: SPARK-19609
> URL: https://issues.apache.org/jira/browse/SPARK-19609
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.1.0
> Reporter: Nick Dimiduk
> Priority: Major
> Labels: bulk-closed
>
> For broadcast inner-joins, where the smaller relation is known to be small
> enough to materialize on a worker, the set of values for all join columns is
> known and fits in memory. Spark should translate these values into a
> {{Filter}} pushed down to the datasource. The common join condition of
> equality, i.e. {{lhs.a == rhs.a}}, can be written as an {{a in ...}} clause.
> An example of pushing such filters is already present in the form of
> {{IsNotNull}} filters via [~sameerag]'s work on SPARK-12957 subtasks.
> This optimization could even work when the smaller relation does not fit
> entirely in memory. This could be done by partitioning the smaller relation
> into N pieces, applying this predicate pushdown for each piece, and unioning
> the results.
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