community: Add support for specifying hybrid search for Databricks vector search (#23528)

**Description:**

Databricks Vector Search recently added support for hybrid
keyword-similarity search.
See [usage
examples](https://docs.databricks.com/en/generative-ai/create-query-vector-search.html#query-a-vector-search-endpoint)
from their documentation.

This PR updates the Langchain vectorstore interface for Databricks to
enable the user to pass the *query_type* parameter to
*similarity_search* to make use of this functionality.
By default, there will not be any changes for existing users of this
interface. To use the new hybrid search feature, it is now possible to
do

```python
# ...
dvs = DatabricksVectorSearch(index)
dvs.similarity_search("my search query", query_type="HYBRID")
```

Or using the retriever:

```python
retriever = dvs.as_retriever(
    search_kwargs={
        "query_type": "HYBRID",
    }
)
retriever.invoke("my search query")
```

---------

Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>
Co-authored-by: Erick Friis <erick@langchain.dev>

libs/community/langchain_community/vectorstores/databricks_vector_search.py

@@ -277,7 +277,13 @@ class DatabricksVectorSearch(VectorStore):
         return True
 
     def similarity_search(
-        self, query: str, k: int = 4, filters: Optional[Any] = None, **kwargs: Any
+        self,
+        query: str,
+        k: int = 4,
+        filters: Optional[Any] = None,
+        *,
+        query_type: Optional[str] = None,
+        **kwargs: Any,
     ) -> List[Document]:
         """Return docs most similar to query.
 
@@ -285,17 +291,24 @@ class DatabricksVectorSearch(VectorStore):
             query: Text to look up documents similar to.
             k: Number of Documents to return. Defaults to 4.
             filters: Filters to apply to the query. Defaults to None.
+            query_type: The type of this query. Supported values are "ANN" and "HYBRID".
 
         Returns:
             List of Documents most similar to the embedding.
         """
         docs_with_score = self.similarity_search_with_score(
-            query=query, k=k, filters=filters, **kwargs
+            query=query, k=k, filters=filters, query_type=query_type, **kwargs
         )
         return [doc for doc, _ in docs_with_score]
 
     def similarity_search_with_score(
-        self, query: str, k: int = 4, filters: Optional[Any] = None, **kwargs: Any
+        self,
+        query: str,
+        k: int = 4,
+        filters: Optional[Any] = None,
+        *,
+        query_type: Optional[str] = None,
+        **kwargs: Any,
     ) -> List[Tuple[Document, float]]:
         """Return docs most similar to query, along with scores.
 
@@ -303,6 +316,7 @@ class DatabricksVectorSearch(VectorStore):
             query: Text to look up documents similar to.
             k: Number of Documents to return. Defaults to 4.
             filters: Filters to apply to the query. Defaults to None.
+            query_type: The type of this query. Supported values are "ANN" and "HYBRID".
 
         Returns:
             List of Documents most similar to the embedding and score for each.
@@ -321,6 +335,7 @@ class DatabricksVectorSearch(VectorStore):
             query_vector=query_vector,
             filters=filters,
             num_results=k,
+            query_type=query_type,
         )
         return self._parse_search_response(search_resp)
 
@@ -343,6 +358,8 @@ class DatabricksVectorSearch(VectorStore):
         fetch_k: int = 20,
         lambda_mult: float = 0.5,
         filters: Optional[Any] = None,
+        *,
+        query_type: Optional[str] = None,
         **kwargs: Any,
     ) -> List[Document]:
         """Return docs selected using the maximal marginal relevance.
@@ -359,6 +376,7 @@ class DatabricksVectorSearch(VectorStore):
                         to maximum diversity and 1 to minimum diversity.
                         Defaults to 0.5.
             filters: Filters to apply to the query. Defaults to None.
+            query_type: The type of this query. Supported values are "ANN" and "HYBRID".
         Returns:
             List of Documents selected by maximal marginal relevance.
         """
@@ -377,6 +395,7 @@ class DatabricksVectorSearch(VectorStore):
             fetch_k,
             lambda_mult=lambda_mult,
             filters=filters,
+            query_type=query_type,
         )
         return docs
 
@@ -387,6 +406,8 @@ class DatabricksVectorSearch(VectorStore):
         fetch_k: int = 20,
         lambda_mult: float = 0.5,
         filters: Optional[Any] = None,
+        *,
+        query_type: Optional[str] = None,
         **kwargs: Any,
     ) -> List[Document]:
         """Return docs selected using the maximal marginal relevance.
@@ -403,6 +424,7 @@ class DatabricksVectorSearch(VectorStore):
                         to maximum diversity and 1 to minimum diversity.
                         Defaults to 0.5.
             filters: Filters to apply to the query. Defaults to None.
+            query_type: The type of this query. Supported values are "ANN" and "HYBRID".
         Returns:
             List of Documents selected by maximal marginal relevance.
         """
@@ -420,6 +442,7 @@ class DatabricksVectorSearch(VectorStore):
             query_vector=embedding,
             filters=filters,
             num_results=fetch_k,
+            query_type=query_type,
         )
 
         embeddings_result_index = (
@@ -449,6 +472,8 @@ class DatabricksVectorSearch(VectorStore):
         embedding: List[float],
         k: int = 4,
         filters: Optional[Any] = None,
+        *,
+        query_type: Optional[str] = None,
         **kwargs: Any,
     ) -> List[Document]:
         """Return docs most similar to embedding vector.
@@ -457,12 +482,13 @@ class DatabricksVectorSearch(VectorStore):
             embedding: Embedding to look up documents similar to.
             k: Number of Documents to return. Defaults to 4.
             filters: Filters to apply to the query. Defaults to None.
+            query_type: The type of this query. Supported values are "ANN" and "HYBRID".
 
         Returns:
             List of Documents most similar to the embedding.
         """
         docs_with_score = self.similarity_search_by_vector_with_score(
-            embedding=embedding, k=k, filters=filters, **kwargs
+            embedding=embedding, k=k, filters=filters, query_type=query_type, **kwargs
         )
         return [doc for doc, _ in docs_with_score]
 
@@ -471,6 +497,8 @@ class DatabricksVectorSearch(VectorStore):
         embedding: List[float],
         k: int = 4,
         filters: Optional[Any] = None,
+        *,
+        query_type: Optional[str] = None,
         **kwargs: Any,
     ) -> List[Tuple[Document, float]]:
         """Return docs most similar to embedding vector, along with scores.
@@ -479,6 +507,7 @@ class DatabricksVectorSearch(VectorStore):
             embedding: Embedding to look up documents similar to.
             k: Number of Documents to return. Defaults to 4.
             filters: Filters to apply to the query. Defaults to None.
+            query_type: The type of this query. Supported values are "ANN" and "HYBRID".
 
         Returns:
             List of Documents most similar to the embedding and score for each.
@@ -493,6 +522,7 @@ class DatabricksVectorSearch(VectorStore):
             query_vector=embedding,
             filters=filters,
             num_results=k,
+            query_type=query_type,
         )
         return self._parse_search_response(search_resp)