Ankur Dave created SPARK-11077:
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Summary: Join elimination in Catalyst
Key: SPARK-11077
URL: https://issues.apache.org/jira/browse/SPARK-11077
Project: Spark
Issue Type: New Feature
Components: SQL
Reporter: Ankur Dave
Assignee: Ankur Dave
Join elimination is a query optimization where certain joins can be eliminated
when followed by projections that only keep columns from one side of the join,
and when certain columns are known to be unique or foreign keys. This can be
very useful for queries involving views and machine-generated queries.
Adding join elimination to Catalyst requires (1) support for unique and foreign
key hints in logical plans, (2) methods in the DataFrame API to let users
provide these hints, and (3) an optimizer rule that eliminates unique key outer
joins and referential integrity joins when followed by an appropriate
projection.
This proposal is described in detail here:
https://docs.google.com/document/d/1-YgQSQywHfAo4PhAT-zOOkFZtVcju99h3dYQq-i9GWQ/edit?usp=sharing
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