HIVE-29637: Iceberg: Incorrect Results for NULL Predicate on Partitio…

[deniskuzZ]

…n Column

What changes were proposed in this pull request?

1. IcebergTableUtil.makeSpecFromName() — a new helper that builds a Hive-compatible partition spec map from Iceberg's PartitionData. When a partition field value is null, it maps it to HIVE_DEFAULT_PARTITION instead of the literal string "null".
2. PartExprEvalUtils.evalExprWithPart() — when evaluating partition predicate expressions, values equal to null or HIVE_DEFAULT_PARTITION are now passed as actual Java null rather than being
   converted through ObjectInspectorConverters.

Why are the changes needed?

Queries with WHERE <partition_col> IS NULL on Iceberg tables returned incorrect results (empty result set).

Does this PR introduce any user-facing change?

No

How was this patch tested?

mvn test -Dtest=TestIcebergCliDriver -Dqfile=iceberg_isnull_partition_pruning.q

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud