Ala Luszczak created SPARK-40059:
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Summary: Row indexes can overshadow user-created data
Key: SPARK-40059
URL: https://issues.apache.org/jira/browse/SPARK-40059
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 3.4.0
Reporter: Ala Luszczak
https://github.com/apache/spark/pull/37228 introduces ability to compute row
indexes, which users can access through `_metadata.row_index` column.
Internally this is achieved with the help of an extra column
`_tmp_metadata_row_index`. When present in the schema sent to parquet reader,
the reader populates it with row indexes, and the values are later placed in
the `_metadata` struct.
While relatively unlikely, it's still possible, that a user might want to
include column `_tmp_metadata_row_index` in their data. In such scenario, the
column will be populated with row indexes, rather than data read from the file.
For repro, search `FileMetadataStructRowIndexSuite.scala` for this Jira ticket
number.
We could introduce some kind of countermeasure to handle this scenario.
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