How to fix spectrum scan error after Parquet schema change ?

Aisyah 25 Reputation points
2026-09-23T06:49:15.1466667+00:00

We’re running into issues where Redshift Spectrum queries fail with a Spectrum Scan Error after a third‑party data pipeline added new columns to our source Parquet files. It looks like the external table definitions are now out of sync with the updated schema. Does anyone know how to properly refresh or update those external table definitions so the queries can run again ?

Windows for business | Windows 365 Business
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HLBui 13,020 Reputation points Independent Advisor
2026-09-23T07:44:59.2933333+00:00

Hi Aisyah •

This is a pretty common hiccup with Redshift Spectrum when the Parquet schema drifts. Basically, Spectrum external tables don’t auto‑refresh when new columns show up, so if the pipeline adds fields, your table definition gets out of sync. The fix is usually to run an ALTER TABLE … ADD COLUMN for each new field so the external table matches the Parquet schema again. If the changes are big or messy, sometimes it’s easier to just drop and recreate the external table with the updated schema pointing to the same location. Another trick: if you’re using Glue Data Catalog, you can update the schema there and Redshift will pick it up. After that, queries should stop throwing the Spectrum Scan Error.

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  1. HLBui 13,020 Reputation points Independent Advisor
    2026-09-29T03:08:45.0766667+00:00

    If everything is okay, don't forget to share your experience with the issue by "Accept answer". If you need more information, feel free to leave a message. We are happy to help!

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