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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 Rust with GCS

When using the Rust deltalake crate with the gcs feature enabled, GCS support is automatically registered at program startup. You don't need to manually call any registration functions.

Before (manual registration - deprecated)

// Legacy approach where applications had to register the handler
deltalake::gcp::register_handlers(None);

let ops = DeltaOps::try_from_uri("gs://bucket/table".parse()?).await?;

After (automatic registration)

// Enable the gcs feature in Cargo.toml:
// deltalake = { version = "0.29", features = ["gcs"] }

use deltalake::DeltaOps;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // The gs:// scheme is recognized automatically
    let ops = DeltaOps::try_from_uri("gs://bucket/table".parse()?).await?;
    Ok(())
}

The automatic registration happens via constructor hooks in the meta-crate (see the CHANGELOG for details).

Note: If you're using deltalake-core and individual storage crates directly (instead of the deltalake meta-crate), you'll still need to call deltalake_gcp::register_handlers(None) manually.

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