[jira] [Commented] (AIRFLOW-5046) Allow GoogleCloudStorageToBigQueryOperator to accept source_objects as a string or otherwise take input from XCom

["Cedrik Neumann (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AIRFLOW-5046?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16899491#comment-16899491 ] 

Cedrik Neumann commented on AIRFLOW-5046:
-----------------------------------------

Yeah, maybe it's a second mechanism after Jinja operating on the result string. I was thinking something like this:
If a string after Jinja defines a xcom address like 
{noformat}
xcom://2019-07-30?key=return_value&task_id=mytask
{noformat}
then the string will be replaced with the value/values of the xcom address.

> Allow GoogleCloudStorageToBigQueryOperator to accept source_objects as a string or otherwise take input from XCom
> -----------------------------------------------------------------------------------------------------------------
>
>                 Key: AIRFLOW-5046
>                 URL: https://issues.apache.org/jira/browse/AIRFLOW-5046
>             Project: Apache Airflow
>          Issue Type: Improvement
>          Components: contrib, gcp
>    Affects Versions: 1.10.2
>            Reporter: Joel Croteau
>            Priority: Minor
>
> `GoogleCloudStorageToBigQueryOperator` should be able to have its `source_objects` dynamically determined by the results of a previous workflow. This is hard to do with it expecting a list, as any template expansion will render as a string. This could be implemented either as a check for whether `source_objects` is a string, and trying to parse it as a list if it is, or a separate argument for a string encoded as a list.
> My particular use case for this is as follows:
>  # A daily DAG scans a GCS bucket for all objects created in the last day and loads them into BigQuery.
>  # To find these objects, a `PythonOperator` scans the bucket and returns a list of object names.
>  # A `GoogleCloudStorageToBigQueryOperator` is used to load these objects into BigQuery.
> The operator should be able to have its list of objects provided by XCom, but there is no functionality to do this, and trying to do a template expansion along the lines of `source_objects='\{{ task_instance.xcom_pull(key="KEY") }}'` doesn't work because this is rendered as a string, which `GoogleCloudStorageToBigQueryOperator` will try to treat as a list, with each character being a single item.



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