2.2 KiB
MEP: Search By Primary Keys
Current state: Under Discussion
ISSUE: [Feature]: Support to search by primary keys #23184
Keywords: Search, ANN
Released: v2.3.0
Summary
Support to search (ANNS) by the query vectors corresponding to the given primary keys.
Motivation
For now, Milvus requires passing the query vectors to do anns, we have to fetch the vectors first if they are in the collection, which is complex and slow.
We need a way to do anns directly for the corresponding vectors of given primary keys, which should be more efficient.
Public Interfaces
Add new field primary_keys in SearchRequest, all SDKs adds new method:
func SearchByPK(
ctx context.Context,
collName string,
partitions []string,
expr string,
outputFields []string,
primaryKeys []entity.PrimaryKey,
vectorField string,
metricType entity.MetricType,
topK int,
sp entity.SearchParam,
opts ...SearchQueryOptionFunc,
) ([]SearchResult, error)
Design Details
Proxy fetches the vectors by primary keys from QueryNodes first, and then search with these vectors.
For better performance, we will add a new RPC interface for QueryNode:
rpc Fetch(FetchRequest) returns (FetchResponse) {}
which only supports to fetch by primary keys, this will be more efficient than the present Query interface.
Compatibility, Deprecation, and Migration Plan
None
Test Plan
Unit Tests
- Test for fetching in segcore
- Test for fetching in QueryNode
- Test for searching by primary keys in Proxy
E2E Tests
| Test Cases | Expected Behavior |
|---|---|
| search by non-existed primary keys | report error |
| search by existed primary keys | return topk results for each query |
| all present tests cases of search by vectors | the same |
Rejected Alternatives
Implement this without adding the Fetch interface, using Query to retrieve the vectors and then search by vectors.
References
None