[jira] [Updated] (SPARK-59902) Detect BYTE_STREAM_SPLIT pages with more encoded values than non-null values in the vectorized reader

["L. C. Hsieh (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-59902?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

L. C. Hsieh updated SPARK-59902:
--------------------------------
    Affects Version/s: 4.3.0
                       4.4.0
                           (was: 5.0.0)

> Detect BYTE_STREAM_SPLIT pages with more encoded values than non-null values in the vectorized reader
> -----------------------------------------------------------------------------------------------------
>
>                 Key: SPARK-59902
>                 URL: https://issues.apache.org/jira/browse/SPARK-59902
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 4.3.0, 4.4.0
>            Reporter: L. C. Hsieh
>            Priority: Major
>
> Follow-up of SPARK-59831.
> For a column with definition levels, the vectorized BYTE_STREAM_SPLIT reader ({{VectorizedByteStreamSplitValuesReader}}) cannot check the number of encoded values against the page header when the page is initialized: the page value count includes nulls, so it is only an upper bound. Let D be the number of non-null definition levels of a page and E the number of encoded values.
> * E < D fails with a {{ParquetDecodingException}} once a read or skip runs past the last encoded value (since SPARK-59831).
> * E > D is never detected, even when the page is read to its end. The values are decoded with the wrong stream stride, so a corrupt data section can return wrong values without an error. For example, an optional FLOAT page with {{num_values = 10}}, 5 non-null levels and 24 data bytes (E = 6) is read as 5 values with a stride of 6.
> This could be detected without {{DataPageV2}}'s {{num_nulls}} (which no reader validates today): when {{VectorizedColumnReader.readBatch}} has consumed all levels of a page ({{readState.valuesToReadInPage == 0}} right after the {{defColumn.readBatch}} / {{repColumn.readBatchRepeated}} calls), all encoded values must have been consumed too. A no-op default hook on {{VectorizedValuesReader}}, implemented by this reader as {{offset == valueCount}}, would check it once per page. Checking only before the next {{readPage()}} would miss the last page of a column chunk.
> A prototype of this check found no false positive on 1454 pages of the BYTE_STREAM_SPLIT tests in the Parquet suites (arrays, nullable columns and column index row ranges, with v1 and v2 pages). Since a false positive would reject valid files, it should be verified on more layouts (nested structs and maps, row ranges on nested columns) before it is added. It is still a late check, so a query that stops before the end of a page does not reach it.



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