How to change nbits for IVFPQ

[AyushP123]

Milvus CPU: v0.10.3 ( Built from Source ).

I want to change nbits for the IVFPQ CPU version from nbits = 8 to nbits = 4 or nbits = 2. However, I am not able to do that with Milvus. Here is the trace of my activity.

I create an index on an empty collection with the following parameters

index_param = {
        "m": 64,
        "nlist": 32,
        "nbits": 4
        }
status = client.create_index(collection_name, IndexType.IVF_PQ, index_param)

I see the status of the index creation as

Status(code=0, message='Build index successfully!')
Create Index Time 0.0040454864501953125

After this, I inserted 5 million vectors into the collection and saw that the row count is 0.
(Status(code=0, message='Success'), {'partitions': [{'row_count': 0, 'segments': None, 'tag': '_default'}], 'row_count': 0})

It seems that Milvus does not recognize nbits as a parameter, hence even though there is a message of 'Build Index Successfully" no index is actually built. Please suggest what should I do to change nbits for IVFPQ.

Suggestion: It seems that you can create an index by passing any string as a parameter and instead of throwing an error, Milvus proceeds with the index creation. It will be better to throw an error to let the user know that a wrong parameter has been passed ( You can recreate this by passing "random" with value set to 1 to IVFPQ and see that the Index is created ).

[shiyu22]

In fact, IVFPQ does not support modifying the nbits parameter, please refer to the vector index for the specific parameters of PQ.

Regarding the insertion failure, please refer to examp.py to check if there is a problem with the data format.

[sahuang]

To clarify: Until v0.11, Milvus will not support modifying nbits parameter during creating index.

However, we plan to add this feature in v0.12.0.