[Bug]: Inconsistent primary field name between Milvus Lite and Cluster/Standalone modes

[shubh3ai]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Pymilvus version: 2.6.1
Milvus server version: v2.6.0 (standalone/cluster)

There's an inconsistency in how primary field names are handled between Milvus Lite and Cluster/Standalone modes.

In Milvus Lite mode, the primary field name defaults to "id", while in Cluster/Standalone mode, it uses the actual configured primary field name (e.g., "vs_reserved_field_id").

Expected Behavior

Both modes should consistently use the same primary field name resolution logic.

Steps/Code To Reproduce behavior

Reproduction:
Create a collection with a custom primary field name in both Lite and Cluster modes
Perform a search operation
Check the primary_field_name in the search results.

Added debug print in `_parse_search_result_data()` inside `client.search_result` file:

    def _parse_search_result_data(
        self,
        res: schema_pb2.SearchResultData,
        round_decimal: Optional[int],
    ) -> List[List[Dict[str, Any]]]:
        _pk_name = res.primary_field_name or "id"
        print("name of the primary field:", _pk_name)


In standalone mode, I can see that the debug statement prints the right configured id, whereas in Lite mode (on disk local db), it prints `id`. 

The schema for collection creation is: 

{
    'auto_id': False, 
    'description': 'Test Async Organization Order Preference List', 
    'fields': [
        {'name': 'metadata', 'description': 'Additional metadata', 'type': <DataType.JSON: 23>}, 
        {'name': 'vs_reserved_field_id', 'description': 'Document UUID', 'type': <DataType.VARCHAR: 21>, 'params': {'max_length': 36}, 'is_primary': True, 'auto_id': False}, 
        {'name': 'vs_reserved_field_vector', 'description': 'Embedding vector', 'type': <DataType.FLOAT_VECTOR: 101>, 'params': {'dim': 768}}
        ], 
    'enable_dynamic_field': False}
    }

Environment details

- Hardware/Softward conditions (OS, CPU, GPU, Memory):
- Method of installation (Docker, or from source): Docker and Lite
- Milvus version (v0.3.1, or v0.4.0):
- Milvus configuration (Settings you made in `server_config.yaml`):

Anything else?

No response

[XuanYang-cn]

Might be related to milvus-lite