[jira] [Created] (SPARK-40059) Row indexes can overshadow user-created data

["Ala Luszczak (Jira)" <ji...@apache.org>]

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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