StreamingJoinStrategy Execution Planning Strategy — Stream-Stream Equi-Joins¶
StreamingJoinStrategy is an execution planning strategy that can plan streaming queries with
Join logical operators of two streaming queries to a <
StreamingJoinStrategy throws an
AnalysisException when applied to a
Join logical operator with no equality predicate:
Stream-stream join without equality predicate is not supported
StreamingJoinStrategy is used when IncrementalExecution is requested to plan a streaming query.
[[logging]] [TIP] ====
StreamingJoinStrategy does not print out any messages to the logs.
StreamingJoinStrategy however uses
ExtractEquiJoinKeys Scala extractor for destructuring
Join logical operators that does print out DEBUG messages to the logs.
Read up on https://jaceklaskowski.gitbooks.io/mastering-spark-sql/spark-sql-ExtractEquiJoinKeys.html[ExtractEquiJoinKeys] in https://bit.ly/spark-sql-internals[The Internals of Spark SQL] online book.
ALL logging level for
org.apache.spark.sql.catalyst.planning.ExtractEquiJoinKeys to see what happens inside.
Add the following line to