Ioana Delaney created SPARK-23757:
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Summary: [Performance] Star schema detection improvements
Key: SPARK-23757
URL: https://issues.apache.org/jira/browse/SPARK-23757
Project: Spark
Issue Type: Sub-task
Components: SQL
Affects Versions: 3.0.0
Reporter: Ioana Delaney
Star schema consists of one or more fact tables referencing a number of
dimension tables. Queries against star schema are expected to run fast because
of the established RI constraints among the tables. In general, star schema
joins are detected using the following conditions:
1. RI constraints (reliable detection)
* Dimension contains a primary key that is being joined to the fact table.
* Fact table contains foreign keys referencing multiple dimension tables.
2. Cardinality based heuristics
* Usually, the table with the highest cardinality is the fact table.
Existing SPARK-17791 uses a combination of the above two conditions to detect
and optimize star joins. With support for informational RI constraints, the
algorithm in SPARK-17791 can be improved with reliable RI detection.
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