[mutianf]

Summary

Validate that rows passed to MutationsBatcher.mutate(row) (and by extension MutationsBatcher.mutate_rows(rows)) are instances of DirectRow and are not bound to a different table, matching the existing validation in Table.mutate_rows().

Problem

When MutationsBatcher was refactored to wrap self.table._table_impl.mutations_batcher(...) directly (#18200) instead of delegating to self.table.mutate_rows(...), two row-validation checks from Table.mutate_rows() were dropped:

1. DirectRow type check (TypeError): Passing a ConditionalRow to batcher.mutate(cond_row) called cond_row._get_mutations() with the default state=None, which returns self._false_pb_mutations and unconditionally sends false-branch mutations via MutateRows without evaluating the row filter predicate. Passing an AppendRow raised a raw AttributeError: 'AppendRow' object has no attribute '_get_mutations' instead of TypeError.
2. Table match check (TableMismatchError): Passing a DirectRow bound to another table silently sent its mutations to batcher.table instead of raising TableMismatchError.

Solution

• Validate isinstance(row, DirectRow) in MutationsBatcher.mutate(), raising TypeError("Bulk processing can not be applied for conditional or append mutations.") if not.
• Validate row.table is None or row.table.name == self.table.name in MutationsBatcher.mutate(), raising TableMismatchError if the row belongs to a different table.
• Document :raises: (TypeError and TableMismatchError) on MutationsBatcher.mutate() and MutationsBatcher.mutate_rows().

Test Plan

• Added unit tests in packages/google-cloud-bigtable/tests/unit/v2_client/test_batcher.py:
  • test_mutations_batcher_mutate_w_bound_table_row
  • test_mutations_batcher_mutate_wrong_row_type (ConditionalRow and AppendRow across mutate and mutate_rows, verifying no mutations are queued)
  • test_mutations_batcher_mutate_table_mismatch (cross-table DirectRow across mutate and mutate_rows)

[gemini-code-assist]

Code Review

This pull request introduces validation checks in MutationsBatcher.mutate to ensure that only DirectRow instances are processed and that the row's table matches the batcher's table. Corresponding unit tests have been added to verify these validations. The review feedback suggests using f-strings instead of % formatting for better readability and correcting a typo ('can not' to 'cannot') in the error message.