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Autoloader issue

The_Demigorgan
New Contributor

I'm trying to ingest data from Parquet files using Autoloader. Now, I have my custom schema, I don't want to infer the schema from the parquet files.

During readstream everything is fine. But during writestream, it is somehow inferring the schema from the files and I'm getting a schema mismatch error.

Any idea why it is happening? Help will be appreciated.

#

1 REPLY 1

Kaniz
Community Manager
Community Manager

Hi @The_Demigorgan, Certainly! When using Autoloader in Databricks for ingesting data from Parquet files, you can enforce your custom schema and avoid schema inference. 

 

Letโ€™s address this issue:

 

Schema Enforcement:

  • Autoloader allows you to explicitly define the schema for your data.
  • By doing so, you ensure that the schema is consistent during both read and write operations.

Common Causes of Schema Mismatch:

  • The schema mismatch error youโ€™re encountering during writestream could be due to several reasons:
    • Conflicting Schema: The schema inferred during readstream might not match the custom schema youโ€™ve defined.
    • Data Type Mismatch: Fields with different data types can cause schema mismatches.
    • Missing Fields: If the custom schema defines additional fields that are not present in the data, it can lead to errors.

Troubleshooting Steps:

  • Ensure that you explicitly set the schema during both read and write operations.
  • Check if there are any conflicting or overriding settings in your code or configuration that may cause the schema to be interpreted differently.
  • Verify that the custom schema youโ€™ve defined aligns with the actual data in your Parquet files.

Additional Considerations:

  • If you encounter issues related to specific fields or data types, review your custom schema and the actual data.
  • Double-check that the schema definition matches the Parquet filesโ€™ structure.

Remember to adapt the above example to your specific use case, ensuring that your custom schema aligns with the data youโ€™re ingesting. If you need further assistance or have more questions, feel free to ask! ๐Ÿš€

 

1: Databricks Community: Autoloader issue 2: Databricks Community: How to enforce schema with Autoloader? 3: Databricks Knowledge Base: Explicit path to data or a defined schema required for Auto Loader 4: Ust Does: Using and Abusing Auto Loaderโ€™s Inferred Schema

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