data serialization ai_generated true

ArrowInvalid: Schema mismatch — Parquet files have incompatible schemas

ID: data/parquet-schema-evolution-incompatible

Also available as: JSON · Markdown
85%Fix Rate
88%Confidence
4Evidence
2023-01-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
any active — — —

Root Cause

Reading multiple Parquet files fails because column types differ between files.

generic

Workarounds

  1. 90% success Use unify_schemas to create a merged schema 
    pa.unify_schemas([f.schema_arrow for f in files])

    Sources: https://arrow.apache.org/docs/python/parquet.html

  2. 88% success Read with pyarrow dataset API which handles schema evolution natively 
    import pyarrow.dataset as ds; dataset = ds.dataset('data/', format='parquet')

    Sources: https://arrow.apache.org/docs/python/dataset.html

Dead Ends

Common approaches that don't work:

  1. Force cast all columns to string 80% fail

    Casting to string destroys type information and breaks downstream numeric operations

  2. Use schema from first file for all files 70% fail

    First file schema may be outdated; newer files with added columns will lose data