Final answer:
The "incompatible Parquet schema" error arises when there is a schema mismatch, likely caused by changing a column from double to string, which alters how data is stored and read. Fixing this requires aligning the Parquet file's schema with the expected schema, either by regenerating files, utilizing schema evolution, or by reconciling schemas prior to data processing.
Step-by-step explanation:
The error "incompatible Parquet schema" typically occurs when there is a mismatch between the schema defined in the Parquet file and the schema expected by the program or service trying to read the file. When you changed a column type from double to string, the underlying data representation in the Parquet file also changed. Parquet has a strict schema enforcement which means that the data types have to be consistent across all the rows in the dataset for a given column.
One common reason for this schema mismatch is due to evolution of the schema over time where an older version of the dataset had different types compared to the new one. To resolve this issue, ensure that the Parquet files are regenerated with the correct schema, or use schema evolution techniques that include backwards compatibility checks and potentially schema merging to accommodate the type change.
If you have to read data with different schemas, one common approach is to implement a schema reconciliation process that aligns the mismatching columns to their correct types before processing the data.