January 2019
Beginner to intermediate
154 pages
4h 31m
English
Content preview from Apache Spark Quick Start Guide
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Join performance
Spark SQL provides a variety of joins, such as the following:
- Shuffle hash join
- Broadcast hash join
- Cartesian join
If the size of both the tables is large and they both are bucketed/partitioned on the same joining field, then shuffle hash join can best suit your needs. It works best when the data is evenly distributed based on the key field and there are enough unique values for that key field to achieve the necessary parallelism. If one of the tables is small in size, you can use broadcast join, which caches the small data on each machine and avoids shuffle.
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