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Re: How do you branch your code with BigQuery?


Hi
   I have created a custom plugin that allows you to branch on the results
of a BigQuery query. The code for it is at
https://github.com/JohnLewisandPartners/custom-airflow-plugins/blob/master/bq_branch/plugins/bq_branch.py.
The version in master only works on airflow 1.10, but there is a branch
called airflow_1.9 that also contains the latest BigQuery hook and so works
on airflow 1.9

   The query you run must return true for all columns - the same as for the
BigQuery check operator, so you may need to rewrite your queries to do this



On Sun, 14 Oct 2018 at 14:16, airflowuser
<airflowuser@xxxxxxxxxxxxxx.invalid> wrote:

> I believe this is quite common case when working with data.
>
> If something : do A
> else: do B
> With coding PythonBranchOperator is the solution.
>
> But when working on Google Cloud there is no way to do this.
> All existed operators are designed to continue or fail on comparison of
> specific value:
> BigQueryValueCheckOperator  with pass_value=500 will continue if 500
> return or fail in any other case. Same for all other CheckOperators. You
> must know the value in advanced for this to work and it's not an actual
> branch but more of a way to stop the workflow if an unexpected result has
> been found.
>
> But how do you handle a scenario where you want to do A or B based on
> condition from a query result? Nothing needs to be failed. just a simple
> branch.
>
> XCOM could solve it. But there is no support for XCOM yet.
>
>
> https://stackoverflow.com/questions/52801318/airflow-how-to-push-xcom-value-from-bigqueryoperator
>
> Say for example:
> the query represent the number of frauds.. if it's <1000 you want to email
> specific users (EmailOperator) , if it's >=1000 you want to run another
> operator and continue the workflow.
>
> Any thoughts on the matter will be appreciated.



-- 
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Anthony Brown
Data Engineer BI Team - John Lewis
Tel : 0787 215 7305
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