Add support for the Negation('$not') operator (#62)

Add support for the Negation(`$not`) operator in PGVector

---------

Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

langchain_postgres/vectorstores.py

@@ -88,7 +88,7 @@ class DistanceStrategy(str, enum.Enum):
     "$ilike",
 }
 
-LOGICAL_OPERATORS = {"$and", "$or"}
+LOGICAL_OPERATORS = {"$and", "$or", "$not"}
 
 SUPPORTED_OPERATORS = (
     set(COMPARISONS_TO_NATIVE)
@@ -1248,26 +1248,25 @@ def _create_filter_clause(self, filters: Any) -> Any:
         """
         if isinstance(filters, dict):
             if len(filters) == 1:
-                # The only operators allowed at the top level are $AND and $OR
+                # The only operators allowed at the top level are $AND, $OR, and $NOT
                 # First check if an operator or a field
                 key, value = list(filters.items())[0]
                 if key.startswith("$"):
                     # Then it's an operator
-                    if key.lower() not in ["$and", "$or"]:
+                    if key.lower() not in ["$and", "$or", "$not"]:
                         raise ValueError(
-                            f"Invalid filter condition. Expected $and or $or "
+                            f"Invalid filter condition. Expected $and, $or or $not "
                             f"but got: {key}"
                         )
                 else:
                     # Then it's a field
                     return self._handle_field_filter(key, filters[key])
 
-                # Here we handle the $and and $or operators
-                if not isinstance(value, list):
-                    raise ValueError(
-                        f"Expected a list, but got {type(value)} for value: {value}"
-                    )
                 if key.lower() == "$and":
+                    if not isinstance(value, list):
+                        raise ValueError(
+                            f"Expected a list, but got {type(value)} for value: {value}"
+                        )
                     and_ = [self._create_filter_clause(el) for el in value]
                     if len(and_) > 1:
                         return sqlalchemy.and_(*and_)
@@ -1279,6 +1278,10 @@ def _create_filter_clause(self, filters: Any) -> Any:
                             "but got an empty dictionary"
                         )
                 elif key.lower() == "$or":
+                    if not isinstance(value, list):
+                        raise ValueError(
+                            f"Expected a list, but got {type(value)} for value: {value}"
+                        )
                     or_ = [self._create_filter_clause(el) for el in value]
                     if len(or_) > 1:
                         return sqlalchemy.or_(*or_)
@@ -1289,9 +1292,29 @@ def _create_filter_clause(self, filters: Any) -> Any:
                             "Invalid filter condition. Expected a dictionary "
                             "but got an empty dictionary"
                         )
+                elif key.lower() == "$not":
+                    if isinstance(value, list):
+                        not_conditions = [
+                            self._create_filter_clause(item) for item in value
+                        ]
+                        not_ = sqlalchemy.and_(
+                            *[
+                                sqlalchemy.not_(condition)
+                                for condition in not_conditions
+                            ]
+                        )
+                        return not_
+                    elif isinstance(value, dict):
+                        not_ = self._create_filter_clause(value)
+                        return sqlalchemy.not_(not_)
+                    else:
+                        raise ValueError(
+                            f"Invalid filter condition. Expected a dictionary "
+                            f"or a list but got: {type(value)}"
+                        )
                 else:
                     raise ValueError(
-                        f"Invalid filter condition. Expected $and or $or "
+                        f"Invalid filter condition. Expected $and, $or or $not "
                         f"but got: {key}"
                     )
             elif len(filters) > 1:

tests/unit_tests/fixtures/filtering_test_cases.py

@@ -81,7 +81,7 @@
 
 TYPE_2_FILTERING_TEST_CASES = [
     # These involve equality checks and other operators
-    # like $ne, $gt, $gte, $lt, $lte, $not
+    # like $ne, $gt, $gte, $lt, $lte
     (
         {"id": 1},
         [1],
@@ -168,7 +168,7 @@
 ]
 
 TYPE_3_FILTERING_TEST_CASES = [
-    # These involve usage of AND and OR operators
+    # These involve usage of AND, OR and NOT operators
     (
         {"$or": [{"id": 1}, {"id": 2}]},
         [1, 2],
@@ -185,6 +185,39 @@
         {"$or": [{"id": 1}, {"id": 2}, {"id": 3}]},
         [1, 2, 3],
     ),
+    # Test for $not operator
+    (
+        {"$not": {"id": 1}},
+        [2, 3],
+    ),
+    (
+        {"$not": [{"id": 1}]},
+        [2, 3],
+    ),
+    (
+        {"$not": {"name": "adam"}},
+        [2, 3],
+    ),
+    (
+        {"$not": [{"name": "adam"}]},
+        [2, 3],
+    ),
+    (
+        {"$not": {"is_active": True}},
+        [2],
+    ),
+    (
+        {"$not": [{"is_active": True}]},
+        [2],
+    ),
+    (
+        {"$not": {"height": {"$gt": 5.0}}},
+        [3],
+    ),
+    (
+        {"$not": [{"height": {"$gt": 5.0}}]},
+        [3],
+    ),
 ]
 
 TYPE_4_FILTERING_TEST_CASES = [

tests/unit_tests/test_vectorstore.py

@@ -992,6 +992,7 @@ async def test_async_pgvector_with_with_metadata_filters_5(
         {"$eq": {}},
         {"$exists": {}},
         {"$exists": 1},
+        {"$not": 2},
     ],
 )
 def test_invalid_filters(pgvector: PGVector, invalid_filter: Any) -> None:
@@ -1016,5 +1017,6 @@ def test_validate_operators() -> None:
         "$lte",
         "$ne",
         "$nin",
+        "$not",
         "$or",
     ]