Hudi Upsert Mock Copy on Write in Python

import copy
from typing import Dict, List, Any

def upsert_copy_on_write(base_records: List[Dict[str, Any]], updates: List[Dict[str, Any]], key_field: str = "id") -> List[Dict[str, Any]]:
    """Simulate Hudi Copy-on-Write upsert: merge updates into a copy of base records."""
    result = copy.deepcopy(base_records)
    update_map = {record[key_field]: record for record in updates}

    for i, record in enumerate(result):
        if record[key_field] in update_map:
            result[i] = update_map.pop(record[key_field])

    result.extend(update_map.values())
    return result

if __name__ == "__main__":
    base = [
        {"id": 1, "name": "Alice", "age": 30},
        {"id": 2, "name": "Bob", "age": 25},
        {"id": 3, "name": "Charlie", "age": 35},
    ]
    changes = [
        {"id": 2, "name": "Robert", "age": 26},
        {"id": 4, "name": "Diana", "age": 28},
    ]
    merged = upsert_copy_on_write(base, changes)
    print(merged)