community[patch]: support hybrid search with threshold in Azure AI Search Retriever (#20907)

Support hybrid search with a score threshold -- similar to what we do
for similarity search.

libs/community/langchain_community/vectorstores/azuresearch.py

@@ -8,6 +8,8 @@ from typing import (
     TYPE_CHECKING,
     Any,
     Callable,
+    ClassVar,
+    Collection,
     Dict,
     Iterable,
     List,
@@ -519,6 +521,17 @@ class AzureSearch(VectorStore):
         ]
         return docs
 
+    def hybrid_search_with_relevance_scores(
+        self, query: str, k: int = 4, **kwargs: Any
+    ) -> List[Tuple[Document, float]]:
+        score_threshold = kwargs.pop("score_threshold", None)
+        result = self.hybrid_search_with_score(query, k=k, **kwargs)
+        return (
+            result
+            if score_threshold is None
+            else [r for r in result if r[1] >= score_threshold]
+        )
+
     def semantic_hybrid_search(
         self, query: str, k: int = 4, **kwargs: Any
     ) -> List[Document]:
@@ -687,9 +700,16 @@ class AzureSearchVectorStoreRetriever(BaseRetriever):
     """Azure Search instance used to find similar documents."""
     search_type: str = "hybrid"
     """Type of search to perform. Options are "similarity", "hybrid",
-    "semantic_hybrid"."""
+    "semantic_hybrid", "similarity_score_threshold", "hybrid_score_threshold"."""
     k: int = 4
     """Number of documents to return."""
+    allowed_search_types: ClassVar[Collection[str]] = (
+        "similarity",
+        "similarity_score_threshold",
+        "hybrid",
+        "hybrid_score_threshold",
+        "semantic_hybrid",
+    )
 
     class Config:
         """Configuration for this pydantic object."""
@@ -701,17 +721,10 @@ class AzureSearchVectorStoreRetriever(BaseRetriever):
         """Validate search type."""
         if "search_type" in values:
             search_type = values["search_type"]
-            if search_type not in (
-                allowed_search_types := (
-                    "similarity",
-                    "similarity_score_threshold",
-                    "hybrid",
-                    "semantic_hybrid",
-                )
-            ):
+            if search_type not in cls.allowed_search_types:
                 raise ValueError(
                     f"search_type of {search_type} not allowed. Valid values are: "
-                    f"{allowed_search_types}"
+                    f"{cls.allowed_search_types}"
                 )
         return values
 
@@ -732,6 +745,13 @@ class AzureSearchVectorStoreRetriever(BaseRetriever):
             ]
         elif self.search_type == "hybrid":
             docs = self.vectorstore.hybrid_search(query, k=self.k, **kwargs)
+        elif self.search_type == "hybrid_score_threshold":
+            docs = [
+                doc
+                for doc, _ in self.vectorstore.hybrid_search_with_relevance_scores(
+                    query, k=self.k, **kwargs
+                )
+            ]
         elif self.search_type == "semantic_hybrid":
             docs = self.vectorstore.semantic_hybrid_search(query, k=self.k, **kwargs)
         else: