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https://issues.apache.org/jira/browse/SPARK-23012?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rick Kramer resolved SPARK-23012.
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Resolution: Fixed
> Support for predicate pushdown and partition pruning when left joining large
> Hive tables
> ----------------------------------------------------------------------------------------
>
> Key: SPARK-23012
> URL: https://issues.apache.org/jira/browse/SPARK-23012
> Project: Spark
> Issue Type: Improvement
> Components: Optimizer
> Affects Versions: 2.2.0
> Reporter: Rick Kramer
> Priority: Major
> Fix For: 2.4.0
>
>
> We have a hive view which left outer joins several large, partitioned orc
> hive tables together on date. When the view is used in a hive query, hive
> pushes date predicates down into the joins and prunes the partitions for all
> tables. When I use this view from pyspark, the predicate is only used to
> prune the left-most table and all partitions from the additional tables are
> selected.
> For example, consider two partitioned hive tables a & b joined in a view:
> create table a (
> a_val string
> )
> partitioned by (ds string)
> stored as orc;
> create table b (
> b_val string
> )
> partitioned by (ds string)
> stored as orc;
> create view example_view as
> select
> a_val
> , b_val
> , ds
> from a
> left outer join b on b.ds = a.ds
> Then in pyspark you might try to query from the view filtering on ds:
> spark.table('example_view').filter(F.col('ds') == '2018-01-01')
> If table a and b are large, this results in a plan that filters a on ds =
> 2018-01-01, but selects scans all partitions of table b.
> If the join in the view is changed to an inner join, the predicate gets
> pushed down to a & b and the partitions are pruned as you'd expect.
> In practice, the view is fairly complex and contains a lot of business logic
> we'd prefer not to replicate in pyspark if we can avoid it.
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