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lidavidm merged 1 commit into from
Jun 3, 2026
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docs: note limitations on Amazon EMR compatibility #51

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Expand Up @@ -120,17 +120,27 @@ These parameters can be specified in the URI as query parameters, or as connecti

## Limitations

Different backends have limitations; some limitations related to data type support are also noted further below.
Different backends and cluster configurations have limitations; some limitations related to data type support are also noted further below.

### HiveServer2/Thrift Protocol

- In Spark 3.x, binary data that does not happen to be valid UTF-8 will be corrupted.
- The client cannot tell whether a timestamp carries a time zone or not; all timestamps are assumed to be in UTC as a result.

### Livy
### Apache Livy

- Only the first 1000 rows of a result set can be fetched. This can be tuned by configuring Spark with `spark.sql.repl.eagerEval.maxNumRows`.
- In general, we have found that performance is worse than with Spark Connect or HiveServer2.
- Connecting to an Amazon EMR (Serverless) cluster via Livy requires setting the `emr-serverless.session.executionRoleArn` session config option to an appropriate role ARN.

### Spark Connect

- In our testing, connecting to an Amazon EMR (Serverless) cluster via Spark Connect does not work; we believe it is an incompatibility in the Spark Connect client library and plan to address this in a future version of the driver.

### Amazon EMR (Serverless)

- Bulk ingest with an AWS Glue catalog is not currently supported as there is no way to specify the `LOCATION` clause.
- Amazon EMR is not currently enabled in our automated integration testing.

## Feature & Type Support

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