EXTENSION property on Redshift UNLOAD not working as expected

Question

Running a basic UNLOAD ([docs](https://docs.aws.amazon.com/redshift/latest/dg/r_UNLOAD.html)) query from redshift like the one below:

```
unload('select id, name from schema.table_name where col = X')
to 's3://bucket-name/files/return_'
iam_role 'arn:aws:iam::XXXXXXXXXXXX:role/some-iam-role'
EXTENSION 'csv'
PARALLEL OFF
NULL AS ''
DELIMITER ','
HEADER
FORMAT CSV
```
Given this query, I would expect the resulting file to have the following key:
```
s3://bucket-name/files/return_000.csv
```

But about 50% of the time, the `.csv` extension is not added, and I get a file with this key:
```
s3://bucket-name/files/return_000
```

Any ideas what could be wrong?

Answer

We are aware of that, we are now running Redshift 1.0.59596, and the issue is still present. The EXTENSION property works for about half the time, but still fails frequently. Without any errors to be seen.

Answer

Extension parameter is a feature that was Released on** January 20, 2023**
It adds a file extension parameter to the UNLOAD command, so file extensions are automatically added to filenames.It supports version **1.0.45698 and above** . Please check to ensure that the version you are using is supported [Cluster Versions for Amazon Redshift](https://docs.aws.amazon.com/redshift/latest/mgmt/cluster-versions.html)

EXTENSION property on Redshift UNLOAD not working as expected

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