[yeshengm]

Are these execution engines internally using Arrow columnar format or are they just exposing Arrow as a client wire format? AFAIK Spark and Presto does not use Arrow as execution columnar format, but just data sources/sinks.

[groceryheist]

You can configure Spark to use arrow for passing data between Java and Python via spark.sql.execution.arrow.pyspark.enabled but yes, Spark uses Java datatypes internally.