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https://issues.apache.org/jira/browse/AIRFLOW-2254?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16427947#comment-16427947
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Kengo Seki commented on AIRFLOW-2254:
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[~sathyaprakashg] Thanks for the comment and submitting a PR!
bq. There is an a argument called unload_options. You can pass PARALLEL OFF as
value to unload_options and it should work.
Yeah, that's right. I meant that it should be documented explicitly. :)
> Fix header output on RedshiftToS3Transfer
> -----------------------------------------
>
> Key: AIRFLOW-2254
> URL: https://issues.apache.org/jira/browse/AIRFLOW-2254
> Project: Apache Airflow
> Issue Type: Bug
> Components: aws, redshift
> Reporter: Kengo Seki
> Assignee: Sathyaprakash Govindasamy
> Priority: Major
>
> The current implementation of RedshiftToS3Transfer is as follows and seems to
> have referred to [this
> post|https://medium.com/carwow-product-engineering/unloading-a-file-from-redshift-to-s3-with-headers-fb707f5480f7].
> {code}
> unload_query = """
> UNLOAD ('SELECT {0}
> UNION ALL
> SELECT {1} FROM {2}.{3}
> ORDER BY 1 DESC')
> TO 's3://{4}/{5}/{3}_'
> with
> credentials
> 'aws_access_key_id={6};aws_secret_access_key={7}'
> {8};
> """.format(column_names, column_castings,
> self.schema, self.table,
> self.s3_bucket, self.s3_key,
> credentials.access_key,
> credentials.secret_key, unload_options)
> {code}
> {{ORDER BY 1 DESC}} is intended to output the header first, but as [this
> post|https://stackoverflow.com/questions/24681214/unloading-from-redshift-to-s3-with-headers#answer-26443374]
> says, it works only if the first column type is not character (e.g. numeric).
> In addition, this query should be used with PARALLEL OFF option, because
> without that, many files are output but only the first one has the header
> line.
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