Support row group skipping for shredded variant columns #15510

Feature Request / Improvement

Iceberg supports writing shredded variant columns to Parquet (PR #14297).

For a query like WHERE variant_get(v, '$.price', 'int') > 100, Iceberg can already skip Parquet files using manifest-level bounds, where the lower/upper bounds for $.price are stored as a Variant-encoded object on the v column's manifest entry (PR #15385).

For better performance, Iceberg should also skip row groups within a file: when $.price is shredded, the physical Parquet column v.typed_value.price.typed_value has standard Parquet min/max statistics. Iceberg should use those stats to skip row groups where max < 100, the same way ParquetMetricsRowGroupFilter handles regular column predicates.

The change is in parquet module, and should work with all engines.

Scope

• Add BoundExtract handling to ParquetMetricsRowGroupFilter
• Map variant path → physical shredded Parquet column
• Unshredded variant columns are not in scope (binary stats are not useful for path-based filtering)
• Test with Spark

Query engine

None

Willingness to contribute

• I can contribute this improvement/feature independently
• I would be willing to contribute this improvement/feature with guidance from the Iceberg community
• I cannot contribute this improvement/feature at this time