Optimizing Conversion between Apache Spark and pandas DataFrames
Apache Arrow is an in-memory columnar data format used in Spark to efficiently transfer data between JVM and Python processes. This is beneficial to Python users that work with pandas and NumPy data. However, its usage is not automatic and requires some minor changes to configuration or code to take full advantage and ensure compatibility.
Convert to/from pandas
Arrow is available as an optimization when converting a Spark DataFrame
to a pandas DataFrame using the call
toPandas() and when creating a
Spark DataFrame from a pandas DataFrame with
To use Arrow when executing these calls, set the Spark configuration
This configuration is disabled by default.
In addition, optimizations enabled by
spark.sql.execution.arrow.enabled could fall back to
a non-Arrow implementation if an error occurs before the computation within Spark.
You can control this behavior using the Spark configuration
import numpy as np import pandas as pd # Enable Arrow-based columnar data transfers spark.conf.set("spark.sql.execution.arrow.enabled", "true") # Generate a pandas DataFrame pdf = pd.DataFrame(np.random.rand(100, 3)) # Create a Spark DataFrame from a pandas DataFrame using Arrow df = spark.createDataFrame(pdf) # Convert the Spark DataFrame back to a pandas DataFrame using Arrow result_pdf = df.select("*").toPandas()
Using the above optimizations with Arrow produces the same results
as when Arrow is not enabled. Even with Arrow,
results in the collection of all records in the DataFrame to the driver
program and should be done on a small subset of the data.
In addition, not all Spark data types are supported and an error can be raised if a
column has an unsupported type. If an error occurs during
Spark falls back to create the DataFrame without Arrow.
Supported SQL types
PyArrow 0.8.0 is installed in Databricks Runtime 4.0-5.1. In Databricks Runtime 5.1 and above,
all Spark SQL data types are supported by Arrow-based conversion except
TimestampType, and nested
BinaryType is supported only when PyArrow is equal to or higher than 0.10.0.