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Dataflow: Schema name changes not working in Data stream to sql template job

Posted on 02-12-2024 01:48 AM
rajnesh_arya_ag
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Reply posted on --/--/---- --:-- AM

I'm using dataflow google provided template (Datastream to sql) to migrate data from avro files stored in google bucket to postgresql database. I'm facing an issue where I'm supplying a map of schema name changes (i.e newSchemaName:oldSchemaName ) in to the dataflow job, still it is searching for old schema name in the destination database. 

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Posted on --/--/---- --:-- AM
ms4446
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Reply posted on --/--/---- --:-- AM

When schema name changes are not recognized by Google Cloud Dataflow's "Datastream to SQL" template, follow these steps to identify and resolve the issue:

Verify Mapping Format:

  • Correct Format: Ensure your schema name change map is a valid JSON object, formatted as {"newSchemaName1":"oldSchemaName1", "newSchemaName2":"oldSchemaName2", ...}.

  • Accuracy Matters: Double-check for accuracy in names, including case sensitivity and absence of typos, as these are crucial for effective mapping.

Review Template Configuration:

  • Parameter Check: Examine the template's parameters related to schema mapping to ensure you're inputting the schema name change map in the designated parameter field, in the correct format.

  • Configuration Alignment: While hardcoded references in the template are unlikely, ensure your configuration aligns perfectly with the template's requirements.

Address Potential Caching Issues:

  • Restart Job: To ensure all configurations are applied afresh, consider restarting the Dataflow job. This step is crucial for recognizing any changes made to the schema mapping or other configurations.

 

Troubleshooting Tactics:

  • Logging: Implement detailed logging to monitor the loading and application of the schema name change map, as well as the SQL queries generated.

  • Error Inspection: Carefully review error messages for references to the old schema name, which can provide clues to the issue.

  • Simplified Testing: Use a minimal test case with fewer schema changes to isolate the problem.

Alternatives:

  • Custom Template Development: If the provided template does not meet your needs, consider developing a custom Dataflow template using Apache Beam for full control over schema mapping.

  • BigQuery as an Intermediate Stage: For complex schema migration scenarios, consider using BigQuery as a staging area due to its flexible schema handling before migrating data to your PostgreSQL destination.

Acknowledge Template Limitations:

  • Consult Documentation: If issues persist after thorough review and testing, it may be due to inherent limitations within the "Datastream to SQL" template regarding schema mapping. Consult the Google Cloud Dataflow documentation for any relevant notes on schema changes.

  • Seek Support: Consider reaching out to Google Cloud support if the documentation and troubleshooting steps do not resolve the issue.

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