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GCS Storage Backend

delta-rs offers native support for using Google Cloud Storage (GCS) as an object storage backend.

You don’t need to install any extra dependencies to read/write Delta tables to GCS with engines that use delta-rs. You do need to configure your GCS access credentials correctly.

Using Application Default Credentials

Application Default Credentials (ADC) is a strategy used by GCS to automatically find credentials based on the application environment.

If you are working from your local machine and have ADC set up then you can read/write Delta tables from GCS directly, without having to pass your credentials explicitly.

Example: Write Delta tables to GCS with Polars

Using Polars, you can write a Delta table to GCS like this:

# create a toy dataframe
import polars as pl
df = pl.DataFrame({"foo": [1, 2, 3, 4, 5]})

# define path
table_path = "gs://bucket/delta-table"

# write Delta to GCS
df.write_delta(table_path)

Passing GCS Credentials explicitly

Alternatively, you can pass GCS credentials to your query engine explicitly.

For Polars, you would do this using the storage_options keyword. This will forward your credentials to the object store library that Polars uses under the hood. Read the Polars documentation and the object store documentation for more information.

Delta Lake on GCS: Required permissions

You will need the following permissions in your GCS account:

  • storage.objects.create
  • storage.objects.delete (only required for uploads that overwrite an existing object)
  • storage.objects.get (only required if you plan on using the Google Cloud CLI)
  • storage.objects.list (only required if you plan on using the Google Cloud CLI)

For more information, see the GCP documentation