[sdrp713]

Fixes #16314.

Description

With MERGE WITH SCHEMA EVOLUTION on DBR 18.3, an UPDATE clause that does not set the newly added column gets an untyped NULL literal for it. The GPU merge processor materializes that literal as INT8, then GpuRapidsProcessDeltaMergeJoinExec fails while concatenating the batches from the different clauses, where the column is STRING: CudfException: Type mismatch in columns to concatenate

This PR types those NULL literals with the target column's type in GpuMergeIntoCommand.updateOutput. The file is shared by the 400db173 and 410db183 shims. The fix mirrors the existing typed null handling for the source row id column in the same file.

Tests in delta_lake_merge_test.py:

• test_delta_merge_not_matched_by_source_schema_evolution_db173 is now parametrized over use_cdf, so the CDC pre/post-image path is covered.
• New test_delta_merge_partial_update_schema_evolution_db173: a MATCHED UPDATE SET dest.b = ... plus INSERT * that evolves the schema, with and without CDF.

On DBR 18.3 the 5 selected tests pass with the fix. With the fix reverted, 4 failed and 1 passed, with the error above in the logs.

Performance tests are not required because the change only sets the type of a null literal in a query that previously failed. It adds no work on the data path.

Checklists

Documentation

• Updated for new or modified user-facing features or behaviors
• No user-facing change

Testing

• Added or modified tests to cover new code paths
• Covered by existing tests
  (Please provide the names of the existing tests in the PR description.)
• Not required

Performance

• Tests ran and results are added in the PR description
• Issue filed with a link in the PR description
• Not required

[greptile-apps]

Confidence Score: 5/5

[Medium impact] No blocking code issue was found in the changes since the previous review.

Summary

Types schema-evolved nulls before nondeterministic update values are evaluated, so nested fields keep their target types.

• GPU MERGE types unset evolved fields before it combines clause outputs.

_{Reviews (4) · Last reviewed commit: "Move struct evaluation" · Reviewed by Greptile}

[sdrp713]

build