Dataflow MongoDB to BigQuery template: How to overwrite BigQuery tables?

[happyhooter]

Hey, I have a question about Dataflow MongoDB to BigQuery template. I can't understand how can I overwrite the table in BigQuery with every new upload from MongoDB? Currently Dataflow template works only in the Append mode and I can't find anything useful in the template settings to change the mode from Append to Overwrite. Please advise how to troubleshoot this.

[ms4446]

The  Dataflow MongoDB to BigQuery template is designed for appending data and doesn't natively support overwriting. To simulate an overwrite functionality, you can implement a workaround:

• Run Dataflow Job: Execute the Dataflow job to load MongoDB data into a staging table in BigQuery.
• Overwrite Destination Table: After the Dataflow job completes, you need a mechanism to replace the contents of the destination table with the newly loaded data.

Option 1: Replace Table:

CREATE OR REPLACE TABLE `project.dataset.destination_table` AS
SELECT * FROM `project.dataset.staging_table`;  -- (Optional staging table)

Option 2: Truncate and Insert:

TRUNCATE TABLE `project.dataset.destination_table`; 
INSERT INTO `project.dataset.destination_table`
SELECT * FROM `project.dataset.staging_table`;  -- (Optional staging table)

• Cloud Function: This can be triggered when the Dataflow job completes. You can use Pub/Sub to trigger the Cloud Function based on the job's completion status.
• Cloud Scheduler: If your data load schedule is predictable, you can use Cloud Scheduler to run the overwrite query periodically.

If you have experience with Apache Beam and Dataflow, you can create a custom template that includes a step to truncate or overwrite the destination table before inserting new data.