databendlabs/databend · error

Unsupported scheme

Error message

Unsupported scheme: {}

What it means

load_bendsave_storage only supports the s3 and fs URI schemes; any other scheme falls into the catch-all arm and returns this error. The operator cannot be constructed because opendal has no configured service for the unknown scheme.

Solutions

1. Use s3:// (with bucket and query params) or fs:// (local path) URIs only.
2. Fix the scheme typo if you meant s3 or fs.
3. For object stores that are S3-compatible (GCS interop, MinIO), expose them via the s3 scheme with the proper endpoint parameter.
4. If another backend is genuinely required, extend the match in load_bendsave_storage with a new Operator::from_iter service branch.

Example fix

// before
let uri = "gcs://my-bucket/backups";
// after
let uri = "s3://my-bucket/backups?endpoint=https://storage.googleapis.com";

// Rust: restrict schemes before calling the loader
const ALLOWED: [&str; 2] = ["s3", "fs"];
let scheme = url::Url::parse(&uri)?.scheme().to_string();
if !ALLOWED.contains(&scheme.as_str()) {
    return Err(format!("scheme '{scheme}' not supported; use s3 or fs"));
}

match load_bendsave_storage(&uri, ...) {
    Ok(op) => op,
    Err(e) if e.to_string().starts_with("Unsupported scheme") => {
        eprintln!("use s3:// or fs:// URI"); Err(e)
    }
    Err(e) => Err(e),
}

When it happens

Trigger: Passing backup/restore a storage URI with a scheme other than s3:// or fs:// (e.g. azblob://, gcs://, oss://, or a typo like s4://).

Common situations: Using URI schemes familiar from other tools (cloud-storage-rs, rclone) that this bendsave build does not implement; typo in the scheme; expecting GCS/Azure support that isn't wired in.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• bendsave requires bucket but it's empty in uri
• URI protocol is not supported yet.
• Unsupported format for
• Unsupported source type. Expected path, pandas.DataFrame…
• Access denied: is outside allowed directories

AI-assisted analysis of databendlabs/databend@288d84d76e (2026-09-11). Data as JSON: /api/errors/2c9fa87b4076dab9. Report an issue: GitHub.

Appendix: source

Thrown at src/bendsave/src/storage.rs:212

    let op = match scheme {
        "s3" => {
            if name.is_empty() {
                return Err(anyhow!(
                    "bendsave requires bucket but it's empty in uri: {}",
                    uri.to_string()
                ));
            }
            map.insert("bucket".to_string(), name.to_string());
            map.insert("root".to_string(), path.to_string());
            let op = Operator::from_iter::<opendal::services::S3>(map)?.finish();
            Ok(op)
        }
        "fs" => {
            map.insert("root".to_string(), format!("/{name}/{path}"));
            let op = Operator::from_iter::<opendal::services::Fs>(map)?.finish();
            Ok(op)
        }
        _ => Err(anyhow::anyhow!("Unsupported scheme: {}", scheme)),
    }?;

    let op = op
        .layer(RetryLayer::default().with_jitter())
        .layer(LoggingLayer::default());
    debug!("epoch storage loaded: {:?}", op.info());
    Ok(op)
}

#[cfg(test)]
mod tests {
    use std::path::Path;

    use opendal::Scheme;

    use super::*;

    #[tokio::test]

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