Empty projection returns the wrong number of rows when column index is enabled

Discovered in Spark, when returning an empty projection from a Parquet file with filter pushdown enabled (typically when doing filter + count), Parquet-Mr returns a wrong number of rows with column index enabled. When the column index feature is disabled, the result is correct.

This happens due to the following:
1. ParquetFileReader::getFilteredRowCount() ( selects row ranges to calculate the row count when column index is enabled.
1. In ColumnIndexFilter ( we filter row ranges and pass the set of paths which in this case is empty.
1. When evaluating the filter, if the column path is not in the set, we would return an empty list of rows ([https://github.com/apache/parquet-mr/blob/0819356a9dafd2ca07c5eab68e2bffeddc3bd3d9/parquet-column/src/main/java/org/apache/parquet/internal/filter2/columnindex/ColumnIndexFilter.java#L178)](https://github.com/apache/parquet-mr/blob/0819356a9dafd2ca07c5eab68e2bffeddc3bd3d9/parquet-column/src/main/java/org/apache/parquet/internal/filter2/columnindex/ColumnIndexFilter.java#L178).) which is always the case for an empty projection.
1. This results in the incorrect number of records reported by the library.

I will provide the full repro later.

 

 

**Reporter**: [Ivan Sadikov](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=ivan.sadikov)
#### Related issues:
- [Filtered parquet data frame count() and show() produce inconsistent results when spark.sql.parquet.filterPushdown is true](https://issues.apache.org/jira/browse/SPARK-39833) (is related to)

_{**Note**: *This issue was originally created as [PARQUET-2170](https://issues.apache.org/jira/browse/PARQUET-2170). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Inizia con ParquetFileReader::getFilteredRowCount() e ColumnIndexFilter, seguendo l’insieme vuoto dei percorsi delle colonne durante la valutazione degli intervalli di righe. Riproduci il caso Spark di filtro più conteggio quando sarà disponibile la riproduzione completa, quindi verifica che una proiezione vuota con indici di colonna e filter pushdown riporti il numero corretto di righe.

Scritto dal modello di indicizzazione a partire dal testo della issue.