HIVE-30064: Report accurate affected-row counts for copy-on-write UPDATE and MERGE

[ryukobayashi]

What changes were proposed in this pull request?

This patch adds matched-row tracking for copy-on-write UPDATE and MERGE operations.

The CoW rewriters append a trailing cow_update_matched boolean marker to their generated projections:

• true for rows produced by the matched UPDATE branch
• false for unchanged survivor rows
• false for MERGE INSERT and DELETE branches

FileSinkOperator uses this marker to count only rows that should contribute to the matched-row count while still writing all rows normally.

The marker-based logic is applied to:

• CopyOnWriteUpdateRewriter
• CopyOnWriteMergeRewriter
• FileSinkOperator

Regression coverage was added through Iceberg CoW tests and a helper for retrieving numModifiedRows from Hive operation status.

Why are the changes needed?

Copy-on-write operations rewrite complete data files. Therefore, the rows sent to the FileSinkOperator include both modified rows and unchanged rows copied from the rewritten files.

For MERGE, a single output also combines multiple logical branches, including matched updates, not-matched inserts, deletes, and unchanged survivor rows.

Previously, FileSinkOperator counted all output rows, so Hive could report an incorrect numModifiedRows value. The reported count could include unchanged rows or rows from other MERGE branches.

The marker makes the logical operation explicit and avoids relying on the physical Tez plan shape or operator layout to determine the count.

Does this PR introduce any user-facing change?

Yes.

The reported affected-row count for copy-on-write UPDATE and MERGE operations is corrected to reflect rows selected by the matched UPDATE operation instead of all rows rewritten by the CoW plan.

The underlying table data and write behavior are unchanged.

For example, a CoW MERGE that updates two rows, inserts two rows, and deletes one row reports the matched update count as 2.

How was this patch tested?

Added Iceberg CoW regression tests for:

• Copy-on-write UPDATE with two matching rows
• Copy-on-write MERGE with two matched updates, two inserts, and one delete

The tests retrieve numModifiedRows through Hive operation status and verify the expected count.

[sonarqubecloud]

Quality Gate passed

Issues
2 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