Apache Spark SQL connector for Google BigQuery (Beta)

The connector supports reading Google BigQuery tables into Spark's DataFrames, and writing DataFrames back into BigQuery. This is done by using the Spark SQL Data Source API to communicate with BigQuery.

Beta Disclaimer

The BigQuery Storage API and this connector are in Beta and are subject to change.

Changes may include, but are not limited to:

• Type conversion
• Partitioning
• Parameters

Breaking changes will be restricted to major and minor versions.

BigQuery Storage API

The Storage API streams data in parallel directly from BigQuery via gRPC without using Google Cloud Storage as an intermediary.

It has a number of advantages over using the previous export-based read flow that should generally lead to better read performance:

Direct Streaming

It does not leave any temporary files in Google Cloud Storage. Rows are read directly from BigQuery servers using an Avro wire format.

Filtering

The new API allows column and predicate filtering to only read the data you are interested in.

Column Filtering

Since BigQuery is backed by a columnar datastore, it can efficiently stream data without reading all columns.

Predicate Filtering

The Storage API supports arbitrary pushdown of predicate filters. Connector version 0.8.0-beta and above support pushdown of arbitrary filters to Bigquery.

There is a known issue in Spark that does not allow pushdown of filters on nested fields. For example - filters like address.city = "Sunnyvale" will not get pushdown to Bigquery.

Dynamic Sharding

The API rebalances records between readers until they all complete. This means that all Map phases will finish nearly concurrently. See this blog article on how dynamic sharding is similarly used in Google Cloud Dataflow.

See Configuring Partitioning for more details.

Requirements

Enable the BigQuery Storage API

Follow these instructions.

Create a Google Cloud Dataproc cluster (Optional)

If you do not have an Apache Spark environment you can create a Cloud Dataproc cluster with pre-configured auth. The following examples assume you are using Cloud Dataproc, but you can use spark-submit on any cluster.

Any Dataproc cluster using the API needs the 'bigquery' or 'cloud-platform' scopes. Dataproc clusters have the 'bigquery' scope by default, so most clusters in enabled projects should work by default e.g.

MY_CLUSTER=...
gcloud dataproc clusters create "$MY_CLUSTER"

Downloading and Using the Connector

The latest version connector of the connector is publicly available in gs://spark-lib/bigquery/spark-bigquery-latest.jar. A Scala 2.12 compiled version exist in gs://spark-lib/bigquery/spark-bigquery-latest_2.12.jar.

The connector is also available from the Maven Central repository. It can be used using the --packages option or the spark.jars.packages configuration property. Use the following value

Scala version	Connector Artifact
Scala 2.11	com.google.cloud.spark:spark-bigquery-with-dependencies_2.11:0.17.1
Scala 2.12	com.google.cloud.spark:spark-bigquery-with-dependencies_2.12:0.17.1

Hello World Example

You can run a simple PySpark wordcount against the API without compilation by running

gcloud dataproc jobs submit pyspark --cluster "$MY_CLUSTER" \
  --jars gs://spark-lib/bigquery/spark-bigquery-latest.jar \
  examples/python/shakespeare.py

Example Codelab

https://codelabs.developers.google.com/codelabs/pyspark-bigquery

Usage

The connector uses the cross language Spark SQL Data Source API:

Reading data from BigQuery

df = spark.read
  .format("bigquery")
  .load("bigquery-public-data.samples.shakespeare")

or the Scala only implicit API:

import com.google.cloud.spark.bigquery._
val df = spark.read.bigquery("bigquery-public-data.samples.shakespeare")

See Shakespeare.scala and shakespeare.py for more information.

Writing data to BigQuery

Writing a DataFrame to BigQuery is done in a similar manner. Notice that the process writes the data first to GCS and then loads it to BigQuery, a GCS bucket must be configured to indicate the temporary data location.

df.write
  .format("bigquery")
  .option("temporaryGcsBucket","some-bucket")
  .save("dataset.table")

The data is temporarily stored using the Apache parquet format. An alternative format is Apache ORC.

The GCS bucket and the format can also be set globally using Spark"s RuntimeConfig like this:

spark.conf.set("temporaryGcsBucket","some-bucket")
df.write
  .format("bigquery")
  .save("dataset.table")

When streaming a DataFrame to BigQuery, each batch is written in the same manner as a non-streaming DataFrame. Note that a HDFS compatible checkpoint location (eg: path/to/HDFS/dir or gs://checkpoint-bucket/checkpointDir) must be specified.

df.writeStream
  .format("bigquery")
  .option("temporaryGcsBucket","some-bucket")
  .option("checkpointLocation", "some-location")
  .option("table", "dataset.table")

Important: The connector does not configure the GCS connector, in order to avoid conflict with another GCS connector, if exists. In order to use the write capabilities of the connector, please configure the GCS connector on your cluster as explained here.

Properties

The API Supports a number of options to configure the read

Property	Meaning	Usage
table	The BigQuery table in the format [[project:]dataset.]table. It is recommended to use the path parameter of load()/save() instead. This option has been deprecated and will be removed in a future version. (Deprecated)	Read/Write
dataset	The dataset containing the table. (Optional unless omitted in table)	Read/Write
project	The Google Cloud Project ID of the table. (Optional. Defaults to the project of the Service Account being used)	Read/Write
parentProject	The Google Cloud Project ID of the table to bill for the export. (Optional. Defaults to the project of the Service Account being used)	Read/Write
maxParallelism	The maximal number of partitions to split the data into. Actual number may be less if BigQuery deems the data small enough. If there are not enough executors to schedule a reader per partition, some partitions may be empty. Important: The old parameter (parallelism) is still supported but in deprecated mode. It will ve removed in version 1.0 of the connector. (Optional. Defaults to one partition per 400MB. See Configuring Partitioning.)	Read
viewsEnabled	Enables the connector to read from views and not only tables. Please read the relevant section before activating this option. (Optional. Defaults to false)	Read
materializationProject	The project id where the materialized view is going to be created (Optional. Defaults to view's project id)	Read
materializationDataset	The dataset where the materialized view is going to be created (Optional. Defaults to view's dataset)	Read
readDataFormat	Data Format for reading from BigQuery. Options : ARROW, AVRO Unsupported Arrow filters are not pushed down and results are filtered later by Spark. (Currently Arrow does not suport disjunction across columns). (Optional. Defaults to AVRO)	Read
optimizedEmptyProjection	The connector uses an optimized empty projection (select without any columns) logic, used for count() execution. This logic takes the data directly from the table metadata or performs a much efficient `SELECT COUNT(*) WHERE...` in case there is a filter. You can cancel the use of this logic byt setting this option to false. (Optional, defaults to true)	Read
createDisposition	Specifies whether the job is allowed to create new tables. The permitted values are: CREATE_IF_NEEDED - Configures the job to create the table if it does not exist. CREATE_NEVER - Configures the job to fail if the table does not exist. This option takes place only in case Spark has decided to write data to the table based on the SaveMode. (Optional. Default to CREATE_IF_NEEDED).	Write
temporaryGcsBucket	The GCS bucket that temporarily holds the data before it is loaded to BigQuery. Required unless set in the Spark configuration (spark.conf.set(...)).	Write
persistentGcsBucket	The GCS bucket that holds the data before it is loaded to BigQuery. If informed, the data won't be deleted after write data into BigQuery.	Write
persistentGcsPath	The GCS path that holds the data before it is loaded to BigQuery. Used only with persistentGcsBucket.	Write
intermediateFormat	The format of the data before it is loaded to BigQuery, values can be either "parquet","orc" or "avro". In order to use the Avro format, the spark-avro package must be added in runtime. (Optional. Defaults to parquet). On write only.	Write
datePartition	The date partition the data is going to be written to. Should be given in the format YYYYMMDD. Can be used to overwrite the data of a single partition, like this: df.write.format("bigquery")   .option("datePartition", "YYYYMMDD")   .mode("overwrite")   .save("table") (Optional). On write only.	Write
partitionField	If field is specified together with `partitionType`, the table is partitioned by this field. The field must be a top-level TIMESTAMP or DATE field. Its mode must be NULLABLE or REQUIRED. If the option is not set for a partitioned table, then the table will be partitioned by pseudo column, referenced via either'_PARTITIONTIME' as TIMESTAMP type, or '_PARTITIONDATE' as DATE type. (Optional).	Write
partitionExpirationMs	Number of milliseconds for which to keep the storage for partitions in the table. The storage in a partition will have an expiration time of its partition time plus this value. (Optional).	Write
partitionType	The only type supported is DAY, which will generate one partition per day. This option is mandatory for a target table to be partitioned. (Optional. Defaults to DAY if PartitionField is specified).	Write
clusteredFields	Comma separated list of non-repeated, top level columns. Clustering is only supported for partitioned tables (Optional).	Write
allowFieldAddition	Adds the ALLOW_FIELD_ADDITION SchemaUpdateOption to the BigQuery LoadJob. Allowed vales are true and false. (Optional. Default to false).	Write
allowFieldRelaxation	Adds the ALLOW_FIELD_RELAXATION SchemaUpdateOption to the BigQuery LoadJob. Allowed vales are true and false. (Optional. Default to false).	Write

Options can also be set outside of the code, using the --conf parameter of spark-submit or --properties parameter of the gcloud dataproc submit spark. In order to use this, prepend the prefix spark.datasource.bigquery. to any of the options, for example spark.conf.set("temporaryGcsBucket", "some-bucket") can also be set as --conf spark.datasource.bigquery.temporaryGcsBucket=some-bucket.

Data types

With the exception of DATETIME and TIME all BigQuery data types directed map into the corresponding Spark SQL data type. Here are all of the mappings:

BigQuery Standard SQL Data Type	Spark SQL Data Type	Notes
BOOL	BooleanType
INT64	LongType
FLOAT64	DoubleType
NUMERIC	DecimalType	This preserves NUMERIC's full 38 digits of precision and 9 digits of scope.
STRING	StringType
BYTES	BinaryType
STRUCT	StructType
ARRAY	ArrayType
TIMESTAMP	TimestampType
DATE	DateType
DATETIME	StringType	Spark has no DATETIME type. Casting to TIMESTAMP uses a configured TimeZone, which defaults to the local timezone (UTC in GCE / Dataproc). We are considering adding an optional TimeZone property to allow automatically converting to TimeStamp, this would be consistent with Spark's handling of CSV/JSON (except they always try to convert when inferring schema, and default to the local timezone)
TIME	LongType	Spark has no TIME type. The generated longs, which indicate microseconds since midnight can be safely cast to TimestampType, but this causes the date to be inferred as the current day. Thus times are left as longs and user can cast if they like. When casting to Timestamp TIME have the same TimeZone issues as DATETIME

Spark ML Data Types Support

The Spark ML Vector and Matrix are supported, including their dense and sparse versions. The data is saved as a BigQuery RECORD. Notice that a suffix is added to the field's description which includes the spark type of the field.

In order to write those types to BigQuery, use the ORC or Avro intermediate format, and have them as column of the Row (i.e. not a field in a struct).

Filtering

The connector automatically computes column and pushdown filters the DataFrame's SELECT statement e.g.

spark.read.bigquery("bigquery-public-data:samples.shakespeare")
  .select("word")
  .where("word = 'Hamlet' or word = 'Claudius'")
  .collect()

filters to the column word and pushed down the predicate filter word = 'hamlet' or word = 'Claudius'.

If you do not wish to make multiple read requests to BigQuery, you can cache the DataFrame before filtering e.g.:

val cachedDF = spark.read.bigquery("bigquery-public-data:samples.shakespeare").cache()
val rows = cachedDF.select("word")
  .where("word = 'Hamlet'")
  .collect()
// All of the table was cached and this doesn't require an API call
val otherRows = cachedDF.select("word_count")
  .where("word = 'Romeo'")
  .collect()

You can also manually specify the filter option, which will override automatic pushdown and Spark will do the rest of the filtering in the client.

Partitioned Tables

The pseudo columns _PARTITIONDATE and _PARTITIONTIME are not part of the table schema. Therefore in order to query by the partitions of partitioned tables do not use the where() method shown above. Instead, add a filter option in the following manner:

val df = spark.read.format("bigquery")
  .option("filter", "_PARTITIONDATE > '2019-01-01'")
  ...
  .load(TABLE)

Configuring Partitioning

By default the connector creates one partition per 400MB in the table being read (before filtering). This should roughly correspond to the maximum number of readers supported by the BigQuery Storage API. This can be configured explicitly with the parallelism property. BigQuery may limit the number of partitions based on server constraints.

Reading From Views

The connector has a preliminary support for reading from BigQuery views. Please note there are a few caveats:

• BigQuery views are not materialized by default, which means that the connector needs to materialize them before it can read them. This process affects the read performance, even before running any collect() or count() action.
• The materialization process can also incur additional costs to your BigQuery bill.
• By default, the materialized views are created in the same project and dataset. Those can be configured by the optional viewMaterializationProject and viewMaterializationDataset options, respectively. These options can also be globally set by calling spark.conf.set(...) before reading the views.
• Reading from views is disabled by default. In order to enable it, either set the viewsEnabled option when reading the specific view (.option("viewsEnabled", "true")) or set it globally by calling spark.conf.set("viewsEnabled", "true").

Using in Jupyter Notebooks

The connector can be used in Jupyter notebooks even if it is not installed on the Spark cluster. It can be added as an external jar in using the following code:

Python:

from pyspark.sql import SparkSession
spark = SparkSession.builder\
  .config("spark.jars.packages", "com.google.cloud.spark:spark-bigquery-with-dependencies_2.11:0.17.1")\
  .getOrCreate()
df = spark.read.format("bigquery")\
  .load("dataset.table")

Scala:

val spark = SparkSession.builder
  .config("spark.jars.packages", "com.google.cloud.spark:spark-bigquery-with-dependencies_2.11:0.17.1")
  .getOrCreate()
val df = spark.read.format("bigquery")
  .load("dataset.table")

In case Spark cluster is using Scala 2.12 (it's optional for Spark 2.4.x, mandatory in 3.0.x), then the relevant package is com.google.cloud.spark:spark-bigquery-with-dependencies_2.12:0.17.1. In order to know which Scala version is used, please run the following code:

Python:

spark.sparkContext._jvm.scala.util.Properties.versionString()

Scala:

scala.util.Properties.versionString

Compiling against the connector

Unless you wish to use the implicit Scala API spark.read.bigquery("TABLE_ID"), there is no need to compile against the connector.

To include the connector in your project:

Maven

<dependency>
  <groupId>com.google.cloud.spark</groupId>
  <artifactId>spark-bigquery-with-dependencies_${scala.version}</artifactId>
  <version>0.17.1</version>
</dependency>

SBT

libraryDependencies += "com.google.cloud.spark" %% "spark-bigquery-with-dependencies" % "0.17.1"

Building the Connector

The connector is built using SBT. Following command creates a jar with shaded dependencies:

sbt assembly

FAQ

What is the Pricing for the Storage API?

See the BigQuery pricing documentation.

I have very few partitions

You can manually set the number of partitions with the maxParallelism property. BigQuery may provide fewer partitions than you ask for. See Configuring Partitioning.

You can also always repartition after reading in Spark.

How do I authenticate outside GCE / Dataproc?

Use a service account JSON key and GOOGLE_APPLICATION_CREDENTIALS as described here.

Credentials can also be provided explicitly either as a parameter or from Spark runtime configuration. It can be passed in as a base64-encoded string directly, or a file path that contains the credentials (but not both).

Example:

spark.read.format("bigquery").option("credentials", "<SERVICE_ACCOUNT_JSON_IN_BASE64>")

or

spark.conf.set("credentials", "<SERVICE_ACCOUNT_JSON_IN_BASE64>")

Alternatively, specify the credentials file name.

spark.read.format("bigquery").option("credentialsFile", "</path/to/key/file>")

or

spark.conf.set("credentialsFile", "</path/to/key/file>")

Another alternative to passing the credentials, is to pass the access token used for authenticating the API calls to the Google Cloud Platform APIs. You can get the access token by running gcloud auth application-default print-access-token.

spark.read.format("bigquery").option("gcpAccessToken", "<acccess-token>")

or

spark.conf.set("gcpAccessToken", "<access-token>")