Add support for KNN vector similarity search (#513)

Co-authored-by: Chayim <chayim@users.noreply.github.com>

aredis_om/__init__.py

@@ -8,6 +8,8 @@
     FindQuery,
     HashModel,
     JsonModel,
+    VectorFieldOptions,
+    KNNExpression,
     NotFoundError,
     QueryNotSupportedError,
     QuerySyntaxError,

aredis_om/model/__init__.py

@@ -4,6 +4,8 @@
     Field,
     HashModel,
     JsonModel,
+    VectorFieldOptions,
+    KNNExpression,
     NotFoundError,
     RedisModel,
 )

aredis_om/model/model.py

@@ -252,6 +252,24 @@ def tree(self):
         return render_tree(self)
 
 
+@dataclasses.dataclass
+class KNNExpression:
+    k: int
+    vector_field: ModelField
+    reference_vector: bytes
+
+    def __str__(self):
+        return f"KNN $K @{self.vector_field.name} $knn_ref_vector"
+
+    @property
+    def query_params(self) -> Dict[str, Union[str, bytes]]:
+        return {"K": str(self.k), "knn_ref_vector": self.reference_vector}
+
+    @property
+    def score_field(self) -> str:
+        return f"__{self.vector_field.name}_score"
+
+
 ExpressionOrNegated = Union[Expression, NegatedExpression]
 
 
@@ -349,8 +367,9 @@ def __init__(
         self,
         expressions: Sequence[ExpressionOrNegated],
         model: Type["RedisModel"],
+        knn: Optional[KNNExpression] = None,
         offset: int = 0,
-        limit: int = DEFAULT_PAGE_SIZE,
+        limit: Optional[int] = None,
         page_size: int = DEFAULT_PAGE_SIZE,
         sort_fields: Optional[List[str]] = None,
         nocontent: bool = False,
@@ -364,13 +383,16 @@ def __init__(
 
         self.expressions = expressions
         self.model = model
+        self.knn = knn
         self.offset = offset
-        self.limit = limit
+        self.limit = limit or (self.knn.k if self.knn else DEFAULT_PAGE_SIZE)
         self.page_size = page_size
         self.nocontent = nocontent
 
         if sort_fields:
             self.sort_fields = self.validate_sort_fields(sort_fields)
+        elif self.knn:
+            self.sort_fields = [self.knn.score_field]
         else:
             self.sort_fields = []
 
@@ -425,11 +447,26 @@ def query(self):
         if self._query:
             return self._query
         self._query = self.resolve_redisearch_query(self.expression)
+        if self.knn:
+            self._query = (
+                self._query
+                if self._query.startswith("(") or self._query == "*"
+                else f"({self._query})"
+            ) + f"=>[{self.knn}]"
         return self._query
 
+    @property
+    def query_params(self):
+        params: List[Union[str, bytes]] = []
+        if self.knn:
+            params += [attr for kv in self.knn.query_params.items() for attr in kv]
+        return params
+
     def validate_sort_fields(self, sort_fields: List[str]):
         for sort_field in sort_fields:
             field_name = sort_field.lstrip("-")
+            if self.knn and field_name == self.knn.score_field:
+                continue
             if field_name not in self.model.__fields__:
                 raise QueryNotSupportedError(
                     f"You tried sort by {field_name}, but that field "
@@ -728,10 +765,27 @@ def resolve_redisearch_query(cls, expression: ExpressionOrNegated) -> str:
         return result
 
     async def execute(self, exhaust_results=True, return_raw_result=False):
-        args = ["ft.search", self.model.Meta.index_name, self.query, *self.pagination]
+        args: List[Union[str, bytes]] = [
+            "FT.SEARCH",
+            self.model.Meta.index_name,
+            self.query,
+            *self.pagination,
+        ]
         if self.sort_fields:
             args += self.resolve_redisearch_sort_fields()
 
+        if self.query_params:
+            args += ["PARAMS", str(len(self.query_params))] + self.query_params
+
+        if self.knn:
+            # Ensure DIALECT is at least 2
+            if "DIALECT" not in args:
+                args += ["DIALECT", "2"]
+            else:
+                i_dialect = args.index("DIALECT") + 1
+                if int(args[i_dialect]) < 2:
+                    args[i_dialect] = "2"
+
         if self.nocontent:
             args.append("NOCONTENT")
 
@@ -917,11 +971,13 @@ def __init__(self, default: Any = Undefined, **kwargs: Any) -> None:
         sortable = kwargs.pop("sortable", Undefined)
         index = kwargs.pop("index", Undefined)
         full_text_search = kwargs.pop("full_text_search", Undefined)
+        vector_options = kwargs.pop("vector_options", None)
         super().__init__(default=default, **kwargs)
         self.primary_key = primary_key
         self.sortable = sortable
         self.index = index
         self.full_text_search = full_text_search
+        self.vector_options = vector_options
 
 
 class RelationshipInfo(Representation):
@@ -935,6 +991,94 @@ def __init__(
         self.link_model = link_model
 
 
+@dataclasses.dataclass
+class VectorFieldOptions:
+    class ALGORITHM(Enum):
+        FLAT = "FLAT"
+        HNSW = "HNSW"
+
+    class TYPE(Enum):
+        FLOAT32 = "FLOAT32"
+        FLOAT64 = "FLOAT64"
+
+    class DISTANCE_METRIC(Enum):
+        L2 = "L2"
+        IP = "IP"
+        COSINE = "COSINE"
+
+    algorithm: ALGORITHM
+    type: TYPE
+    dimension: int
+    distance_metric: DISTANCE_METRIC
+
+    # Common optional parameters
+    initial_cap: Optional[int] = None
+
+    # Optional parameters for FLAT
+    block_size: Optional[int] = None
+
+    # Optional parameters for HNSW
+    m: Optional[int] = None
+    ef_construction: Optional[int] = None
+    ef_runtime: Optional[int] = None
+    epsilon: Optional[float] = None
+
+    @staticmethod
+    def flat(
+        type: TYPE,
+        dimension: int,
+        distance_metric: DISTANCE_METRIC,
+        initial_cap: Optional[int] = None,
+        block_size: Optional[int] = None,
+    ):
+        return VectorFieldOptions(
+            algorithm=VectorFieldOptions.ALGORITHM.FLAT,
+            type=type,
+            dimension=dimension,
+            distance_metric=distance_metric,
+            initial_cap=initial_cap,
+            block_size=block_size,
+        )
+
+    @staticmethod
+    def hnsw(
+        type: TYPE,
+        dimension: int,
+        distance_metric: DISTANCE_METRIC,
+        initial_cap: Optional[int] = None,
+        m: Optional[int] = None,
+        ef_construction: Optional[int] = None,
+        ef_runtime: Optional[int] = None,
+        epsilon: Optional[float] = None,
+    ):
+        return VectorFieldOptions(
+            algorithm=VectorFieldOptions.ALGORITHM.HNSW,
+            type=type,
+            dimension=dimension,
+            distance_metric=distance_metric,
+            initial_cap=initial_cap,
+            m=m,
+            ef_construction=ef_construction,
+            ef_runtime=ef_runtime,
+            epsilon=epsilon,
+        )
+
+    @property
+    def schema(self):
+        attr = []
+        for k, v in vars(self).items():
+            if k == "algorithm" or v is None:
+                continue
+            attr.extend(
+                [
+                    k.upper() if k != "dimension" else "DIM",
+                    str(v) if not isinstance(v, Enum) else v.name,
+                ]
+            )
+
+        return " ".join([f"VECTOR {self.algorithm.name} {len(attr)}"] + attr)
+
+
 def Field(
     default: Any = Undefined,
     *,
@@ -964,6 +1108,7 @@ def Field(
     sortable: Union[bool, UndefinedType] = Undefined,
     index: Union[bool, UndefinedType] = Undefined,
     full_text_search: Union[bool, UndefinedType] = Undefined,
+    vector_options: Optional[VectorFieldOptions] = None,
     schema_extra: Optional[Dict[str, Any]] = None,
 ) -> Any:
     current_schema_extra = schema_extra or {}
@@ -991,6 +1136,7 @@ def Field(
         sortable=sortable,
         index=index,
         full_text_search=full_text_search,
+        vector_options=vector_options,
         **current_schema_extra,
     )
     field_info._validate()
@@ -1083,6 +1229,10 @@ def __new__(cls, name, bases, attrs, **kwargs):  # noqa C901
                     new_class._meta.primary_key = PrimaryKey(
                         name=field_name, field=field
                     )
+                if field.field_info.vector_options:
+                    score_attr = f"_{field_name}_score"
+                    setattr(new_class, score_attr, None)
+                    new_class.__annotations__[score_attr] = Union[float, None]
 
         if not getattr(new_class._meta, "global_key_prefix", None):
             new_class._meta.global_key_prefix = getattr(
@@ -1216,8 +1366,12 @@ def db(cls):
         return cls._meta.database
 
     @classmethod
-    def find(cls, *expressions: Union[Any, Expression]) -> FindQuery:
-        return FindQuery(expressions=expressions, model=cls)
+    def find(
+        cls,
+        *expressions: Union[Any, Expression],
+        knn: Optional[KNNExpression] = None,
+    ) -> FindQuery:
+        return FindQuery(expressions=expressions, knn=knn, model=cls)
 
     @classmethod
     def from_redis(cls, res: Any):
@@ -1237,7 +1391,7 @@ def to_string(s):
         for i in range(1, len(res), step):
             if res[i + offset] is None:
                 continue
-            fields = dict(
+            fields: Dict[str, str] = dict(
                 zip(
                     map(to_string, res[i + offset][::2]),
                     map(to_string, res[i + offset][1::2]),
@@ -1247,6 +1401,9 @@ def to_string(s):
             if fields.get("$"):
                 json_fields = json.loads(fields.pop("$"))
                 doc = cls(**json_fields)
+                for k, v in fields.items():
+                    if k.startswith("__") and k.endswith("_score"):
+                        setattr(doc, k[1:], float(v))
             else:
                 doc = cls(**fields)
 
@@ -1474,7 +1631,13 @@ def schema_for_type(cls, name, typ: Any, field_info: PydanticFieldInfo):
             embedded_cls = embedded_cls[0]
             schema = cls.schema_for_type(name, embedded_cls, field_info)
         elif any(issubclass(typ, t) for t in NUMERIC_TYPES):
-            schema = f"{name} NUMERIC"
+            vector_options: Optional[VectorFieldOptions] = getattr(
+                field_info, "vector_options", None
+            )
+            if vector_options:
+                schema = f"{name} {vector_options.schema}"
+            else:
+                schema = f"{name} NUMERIC"
         elif issubclass(typ, str):
             if getattr(field_info, "full_text_search", False) is True:
                 schema = (
@@ -1623,10 +1786,22 @@ def schema_for_type(
             # Not a class, probably a type annotation
             field_is_model = False
 
+        vector_options: Optional[VectorFieldOptions] = getattr(
+            field_info, "vector_options", None
+        )
+        try:
+            is_vector = vector_options and any(
+                issubclass(get_args(typ)[0], t) for t in NUMERIC_TYPES
+            )
+        except IndexError:
+            raise RedisModelError(
+                f"Vector field '{name}' must be annotated as a container type"
+            )
+
         # When we encounter a list or model field, we need to descend
         # into the values of the list or the fields of the model to
         # find any values marked as indexed.
-        if is_container_type:
+        if is_container_type and not is_vector:
             field_type = get_origin(typ)
             embedded_cls = get_args(typ)
             if not embedded_cls:
@@ -1689,7 +1864,9 @@ def schema_for_type(
             )
 
             # TODO: GEO field
-            if parent_is_container_type or parent_is_model_in_container:
+            if is_vector and vector_options:
+                schema = f"{path} AS {index_field_name} {vector_options.schema}"
+            elif parent_is_container_type or parent_is_model_in_container:
                 if typ is not str:
                     raise RedisModelError(
                         "In this Preview release, list and tuple fields can only "