Presto 337 Documentation

7.2. BigQuery Connector

7.2. BigQuery Connector#

The BigQuery connector allows querying the data stored in BigQuery. This can be used to join data between different systems like BigQuery and Hive. The connector uses the BigQuery Storage API to read the data from the tables.

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

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.

Column Filtering

The new API allows column filtering to only read the data you are interested in. Backed by a columnar datastore, it can efficiently stream data without reading all columns.

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.

Requirements#

Enable the BigQuery Storage API#

Follow these instructions.

Authentication#

On GCE/Dataproc the authentication is taken from the machine’s role.

Outside GCE/Dataproc you have 3 options:

  • Use a service account JSON key and GOOGLE_APPLICATION_CREDENTIALS as described here.
  • Set bigquery.credentials-key in the catalog properties file. It should contain the contents of the JSON file, encoded using base64.
  • Set bigquery.credentials-file in the catalog properties file. It should point to the location of the JSON file.

Configuration#

To configure the BigQuery connector, create a catalog properties file in etc/catalog named, for example, bigquery.properties, to mount the BigQuery connector as the bigquery catalog. Create the file with the following contents, replacing the connection properties as appropriate for your setup:

connector.name=bigquery
bigquery.project-id=<your Google Cloud Platform project id>

Multiple GCP Projects#

The BigQuery connector can only access a single GCP project.Thus, if you have data in multiple GCP projects, You need to create several catalogs, each pointingto a different GCP project. For example, if you have two GCP projects, one for the sales and one for analytics, you can create two properties files in etc/catalog named sales.properties and analytics.properties, both having connector.name=bigquery but with different project-id. This will create the two catalogs, sales and analytics respectively.

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 bigquery.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.
  • 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 bigquery.view-materialization-project and bigquery.view-materialization-dataset properties, respectively. The service account must have write permission to the project and the dataset in order to materialize the view.
  • Reading from views is disabled by default. In order to enable it, set the bigquery.views-enabled configuration property to true.

Configuration Properties#

All configuration properties are optional.

Property Description Default
bigquery.project-id The Google Cloud Project ID where the data reside Taken from the service account
bigquery.parent-project-id The project ID Google Cloud Project to bill for the export Taken from the service account
bigquery.parallelism The number of partitions to split the data into The number of executors
bigquery.views-enabled Enables the connector to read from views and not only tables. Please read this section before enabling this feature. false
bigquery.view-materialization-project The project where the materialized view is going to be created The view’s project
bigquery.view-materialization-dataset The dataset where the materialized view is going to be created The view’s dataset
bigquery.max-read-rows-retries The number of retries in case of retryable server issues 3
bigquery.credentials-key The base64 encoded credentials key None. See authentication
bigquery.credentials-file The path to the JSON credentials file None. See authentication

Data Types#

With a few exceptions, all BigQuery types are mapped directly to their Presto counterparts. Here are all the mappings:

BigQuery Presto Notes
BOOLEAN BOOLEAN  
BYTES VARBINARY  
DATE DATE  
DATETIME TIMESTAMP  
FLOAT DOUBLE  
GEOGRAPHY VARCHAR In Well-known text (WKT) format
INTEGER BIGINT  
NUMERIC DECIMAL(38,9)  
RECORD ROW  
STRING VARCHAR  
TIME TIME_WITH_TIME_ZONE Time zone is UTC
TIMESTAMP TIMESTAMP_WITH_TIME_ZONE Time zone is UTC

FAQ#

What is the Pricing for the Storage API?#

See the BigQuery pricing documentation.