Support distance threshold override (#202)

At runtime, we should extend the ability to override the distance
threshold if provided. This is also how the semantic router works.
Parity between the extensions is key here (in terms of functionality)

redisvl/extensions/llmcache/semantic.py

@@ -233,6 +233,7 @@ def check(
         num_results: int = 1,
         return_fields: Optional[List[str]] = None,
         filter_expression: Optional[FilterExpression] = None,
+        distance_threshold: Optional[float] = None,
     ) -> List[Dict[str, Any]]:
         """Checks the semantic cache for results similar to the specified prompt
         or vector.
@@ -255,6 +256,8 @@ def check(
             filter_expression (Optional[FilterExpression]) : Optional filter expression
                 that can be used to filter cache results. Defaults to None and
                 the full cache will be searched.
+            distance_threshold (Optional[float]): The threshold for semantic
+                vector distance.
 
         Returns:
             List[Dict[str, Any]]: A list of dicts containing the requested
@@ -274,9 +277,12 @@ def check(
         if not (prompt or vector):
             raise ValueError("Either prompt or vector must be specified.")
 
+        # overrides
+        distance_threshold = distance_threshold or self._distance_threshold
+        return_fields = return_fields or self.return_fields
         vector = vector or self._vectorize_prompt(prompt)
+
         self._check_vector_dims(vector)
-        return_fields = return_fields or self.return_fields
 
         if not isinstance(return_fields, list):
             raise TypeError("return_fields must be a list of field names")
@@ -285,7 +291,7 @@ def check(
             vector=vector,
             vector_field_name=self.vector_field_name,
             return_fields=self.return_fields,
-            distance_threshold=self._distance_threshold,
+            distance_threshold=distance_threshold,
             num_results=num_results,
             return_score=True,
             filter_expression=filter_expression,

redisvl/extensions/session_manager/semantic_session.py

@@ -137,6 +137,7 @@ def get_relevant(
         fall_back: bool = False,
         session_tag: Optional[str] = None,
         raw: bool = False,
+        distance_threshold: Optional[float] = None,
     ) -> Union[List[str], List[Dict[str, str]]]:
         """Searches the chat history for information semantically related to
         the specified prompt.
@@ -151,10 +152,12 @@ def get_relevant(
             as_text (bool): Whether to return the prompts and responses as text
             or as JSON
             top_k (int): The number of previous messages to return. Default is 5.
-            fall_back (bool): Whether to drop back to recent conversation history
-                if no relevant context is found.
             session_tag (Optional[str]): Tag to be added to entries to link to a specific
                 session. Defaults to instance uuid.
+            distance_threshold (Optional[float]): The threshold for semantic
+                vector distance.
+            fall_back (bool): Whether to drop back to recent conversation history
+                if no relevant context is found.
             raw (bool): Whether to return the full Redis hash entry or just the
                 message.
 
@@ -169,6 +172,9 @@ def get_relevant(
         if top_k == 0:
             return []
 
+        # override distance threshold
+        distance_threshold = distance_threshold or self._distance_threshold
+
         return_fields = [
             self.session_field_name,
             self.role_field_name,
@@ -187,7 +193,7 @@ def get_relevant(
             vector=self._vectorizer.embed(prompt),
             vector_field_name=self.vector_field_name,
             return_fields=return_fields,
-            distance_threshold=self._distance_threshold,
+            distance_threshold=distance_threshold,
             num_results=top_k,
             return_score=True,
             filter_expression=session_filter,

tests/integration/test_llmcache.py

@@ -95,7 +95,7 @@ def test_store_and_check(cache, vectorizer):
     vector = vectorizer.embed(prompt)
 
     cache.store(prompt, response, vector=vector)
-    check_result = cache.check(vector=vector)
+    check_result = cache.check(vector=vector, distance_threshold=0.4)
 
     assert len(check_result) == 1
     print(check_result, flush=True)

tests/integration/test_session_manager.py

@@ -463,6 +463,10 @@ def test_semantic_add_and_get_relevant(semantic_session):
     semantic_session.set_distance_threshold(0.5)
     default_context = semantic_session.get_relevant("list of fruits and vegetables")
     assert len(default_context) == 5  # 2 pairs of prompt:response, and system
+    assert default_context == semantic_session.get_relevant(
+        "list of fruits and vegetables",
+        distance_threshold=0.5
+    )
 
     # test tool calls can also be returned
     context = semantic_session.get_relevant("winter sports like skiing")