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https://issues.apache.org/jira/browse/SPARK-15302?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hyukjin Kwon resolved SPARK-15302.
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Resolution: Incomplete
> Implement FK/PK "rely novalidate" constraints for better CBO
> ------------------------------------------------------------
>
> Key: SPARK-15302
> URL: https://issues.apache.org/jira/browse/SPARK-15302
> Project: Spark
> Issue Type: New Feature
> Components: Optimizer, Spark Core
> Affects Versions: 2.0.0
> Reporter: Ruslan Dautkhanov
> Priority: Major
> Labels: bulk-closed
>
> Oracle has "RELY NOVALIDATE" option for constraints.. Could be easier for
> Hive to start with something like that for PK/FK constraints. So CBO has more
> information for optimizations. It does not have to actually check if that
> constraint is relationship is true; it can just "rely" on that constraint.
> RELY clause:
> https://docs.oracle.com/database/121/SQLRF/clauses002.htm#SQLRF52223
> "Overview of Constraint States":
> https://docs.oracle.com/database/121/DWHSG/schemas.htm#DWHSG9053
> - Enforcement
> - Validation
> - Belief
> So FK/PK with "rely novalidate" will have Enforcement&Validate disabled but
> Belief = RELY as it is possible to do in Oracle and now in Hive (HIVE-13076).
> It opens a lot of ways to do additional ways to optimize execution plans.
> As explained in Tom Kyte's "Metadata matters"
> http://www.peoug.org/wp-content/uploads/2009/12/MetadataMatters_PEOUG_Day2009_TKyte.pdf
> pp.30 - "Tell us how the tables relate and we can remove them from the
> plan...".
> pp.35 - "Tell us how the tables relate and we have more access paths
> available...".
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