Hidden Hits Parameter Not Working in Multi-Search Vector Query

[CharafLachachi]

Description

When running a multi-search vector query on a collection in Typesense Cloud, the items specified in the hidden_hits parameter are still being retrieved in the results.

Steps to reproduce

1. Create a collection with the following schema:

var collectionName = "people";
var collectionSchema = new Schema
(
    name: collectionName,
    fields:
    [
        new Field("id", FieldType.String, false),
        new Field("firstname", FieldType.String, false),
        new Field("lastname", FieldType.String, false),
        new Field("biography", FieldType.String, false),
        new Field("country", FieldType.String, false),
        new("embedding", FieldType.FloatArray, embed: new AutoEmbeddingConfig(
                        new Collection<string> { "biography", "country" },
                        new ModelConfig(llmModel)))
   ]
);

2. Run the following multi-search vector query:

{
    "searches": [
        {
            "collection": "people",
            "vector_query": "embedding:([],id:8A0E3E51-D0C2-4F2C-8201-32EF9DFD065F,k:6)",
            "q": "*",
            "sort_by": "_vector_distance:desc",
            "hidden_hits": "31E87C56-61BC-461B-B3A8-5D30516A3354",
            "exclude_fields": "embedding"
        }
    ]
}

Expected Behavior

The items specified in the hidden_hits parameter should not be included in the search results.

Actual Behavior

The items specified in the hidden_hits parameter are still being retrieved in the search results.

Metadata

Typesense Version: 0.26.0

OS: Typesense Cloud

Additional Information
I have attached a C# console project that reproduces the issue. You can find the project
TypeSenseVectorQueryIssue.zip

[Nushio]

We stumbled upon the same issue when doing vector searches.

Our workaround is to use the new filter_by id for Typese v26, and include the hidden hits as a list of id:!=

Not sure if there's any performance hits for doing this, but it solved our issue.