microsoft/semantic-kernel · error · VectorStoreModelException

Search type '{search_type}' is not supported.

Error message

Search type '{search_type}' is not supported.

What it means

The Cosmos DB NoSQL store only implements two search modes: VECTOR (pure VectorDistance) and KEYWORD_HYBRID (RRF of VectorDistance and FullTextScore). Any other SearchType enum value falls through to an else branch and raises a VectorStoreModelException. The connector simply has no code path for additional search types, so the request is rejected before any query is built.

Source

Thrown at python/semantic_kernel/connectors/azure_cosmos_db.py:843

        if vector_field.distance_function not in DISTANCE_FUNCTION_MAP_NOSQL:
            raise VectorStoreModelException(
                f"Distance function '{vector_field.distance_function}' is not supported by Azure Cosmos DB NoSQL."
            )
        # Cosmos DB VectorDistance function only accepts 2 parameters: field and vector
        # Distance function is configured in the vector index, not in the query
        if search_type == SearchType.VECTOR:
            distance_clause = f"VectorDistance(c.{vector_field_name}, @vector)"
        elif search_type == SearchType.KEYWORD_HYBRID:
            # Hybrid search: requires both a vector and keywords
            params.append({"name": "@keywords", "value": values})
            text_field = options.additional_property_name
            if not text_field:
                raise VectorStoreModelException("Hybrid search requires 'keyword_field_name' in options.")
            distance_clause = (
                f"RRF(VectorDistance(c.{vector_field_name}, @vector), FullTextScore(c.{text_field}, @keywords))"
            )
        else:
            raise VectorStoreModelException(f"Search type '{search_type}' is not supported.")
        query = (
            f"SELECT TOP @top {select_clause}, "  # nosec: B608
            f"{distance_clause} as {NOSQL_SCORE_PROPERTY_NAME} "  # nosec: B608
            "FROM c "
            f"{where_clauses}"  # nosec: B608
            f"ORDER BY {distance_clause}"  # nosec: B608
        )

        container_proxy = await self._get_container_proxy(self.collection_name, **kwargs)
        try:
            results = container_proxy.query_items(query, parameters=params)
        except Exception as exc:
            raise VectorSearchExecutionException("Failed to search items.") from exc
        return KernelSearchResults(
            results=self._get_vector_search_results_from_results(results, options),
            total_count=None,
        )

View on GitHub (pinned to c028a0c7dc)

Solutions

1. Restrict the SearchType you pass to SearchType.VECTOR or SearchType.KEYWORD_HYBRID when using the Cosmos NoSQL store.
2. If you need text-only keyword search, that mode is not supported by this connector; switch to a connector that implements it or run a manual Cosmos SQL query.
3. Guard dynamic search_type values before calling search so unsupported types are rejected with your own validation rather than the library exception.

Example fix

// before
results = await store.search(values, VectorSearchOptions(top=5))  # search_type resolved to unsupported value
// after
if search_type not in (SearchType.VECTOR, SearchType.KEYWORD_HYBRID):
    raise ValueError("Cosmos NoSQL only supports VECTOR and KEYWORD_HYBRID")
results = await store.search(values, VectorSearchOptions(top=5))

from semantic_kernel.data import SearchType
SUPPORTED = {SearchType.VECTOR, SearchType.KEYWORD_HYBRID}
if search_type not in SUPPORTED:
    raise ValueError(f"Unsupported search_type for Cosmos NoSQL: {search_type}")

def is_supported_cosmos_search(st: SearchType) -> bool:
    return st in (SearchType.VECTOR, SearchType.KEYWORD_HYBRID)

When it happens

Trigger: Calling _inner_search / the public search API with a SearchType value that is neither SearchType.VECTOR nor SearchType.KEYWORD_HYBRID (e.g. a pure keyword/text-only search, or a future enum member the installed version does not handle).

Common situations: A caller passes search_type based on dynamic/user input without restricting it to the two supported values, or code written against another connector (which supports more SearchType members) is pointed at the Cosmos NoSQL store.

Related errors

• Hybrid search requires 'keyword_field_name' in options.
• Distance function '{field.distance_function}' is not support
• The collection name is required, can be passed directly or t
• Failed to create Azure CosmosDB for MongoDB settings.
• The name of the Azure Cosmos DB NoSQL database is missing.

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/9c21ce8f4ace7334. Report an issue: GitHub.