add object ranker

metagpt/rag/factories/ranker.py

@@ -6,14 +6,24 @@ from llama_index.core.postprocessor.types import BaseNodePostprocessor
 from llama_index.postprocessor.colbert_rerank import ColbertRerank
 
 from metagpt.rag.factories.base import ConfigBasedFactory
-from metagpt.rag.schema import BaseRankerConfig, ColbertRerankConfig, LLMRankerConfig
+from metagpt.rag.rankers.object_ranker import ObjectSortPostprocessor
+from metagpt.rag.schema import (
+    BaseRankerConfig,
+    ColbertRerankConfig,
+    LLMRankerConfig,
+    ObjectRankerConfig,
+)
 
 
 class RankerFactory(ConfigBasedFactory):
     """Modify creators for dynamically instance implementation."""
 
     def __init__(self):
-        creators = {LLMRankerConfig: self._create_llm_ranker, ColbertRerankConfig: self._create_colbert_ranker}
+        creators = {
+            LLMRankerConfig: self._create_llm_ranker,
+            ColbertRerankConfig: self._create_colbert_ranker,
+            ObjectRankerConfig: self._create_object_ranker,
+        }
         super().__init__(creators)
 
     def get_rankers(self, configs: list[BaseRankerConfig] = None, **kwargs) -> list[BaseNodePostprocessor]:
@@ -30,6 +40,9 @@ class RankerFactory(ConfigBasedFactory):
     def _create_colbert_ranker(self, config: ColbertRerankConfig, **kwargs) -> LLMRerank:
         return ColbertRerank(**config.model_dump())
 
+    def _create_object_ranker(self, config: ObjectRankerConfig, **kwargs) -> LLMRerank:
+        return ObjectSortPostprocessor(**config.model_dump())
+
     def _extract_llm(self, config: BaseRankerConfig = None, **kwargs) -> LLM:
         return self._val_from_config_or_kwargs("llm", config, **kwargs)
 

metagpt/rag/rankers/object_ranker.py

@@ -0,0 +1,54 @@
+"""Object ranker."""
+
+import heapq
+import json
+from typing import Literal, Optional
+
+from llama_index.core.postprocessor.types import BaseNodePostprocessor
+from llama_index.core.schema import NodeWithScore, QueryBundle
+from pydantic import Field
+
+from metagpt.rag.schema import ObjectNode
+
+
+class ObjectSortPostprocessor(BaseNodePostprocessor):
+    """Sorted by object's field, desc or asc.
+
+    Assumes nodes is list of ObjectNode with score.
+    """
+
+    field_name: str = Field(..., description="field name of the object, field's value must can be compared.")
+    order: Literal["desc", "asc"] = Field(default="desc", description="the direction of order.")
+    top_n: int = 5
+
+    @classmethod
+    def class_name(cls) -> str:
+        return "ObjectSortPostprocessor"
+
+    def _postprocess_nodes(
+        self,
+        nodes: list[NodeWithScore],
+        query_bundle: Optional[QueryBundle] = None,
+    ) -> list[NodeWithScore]:
+        """Postprocess nodes."""
+        if query_bundle is None:
+            raise ValueError("Missing query bundle in extra info.")
+
+        if not nodes:
+            return []
+
+        self._check_metadata(nodes[0].node)
+        sort_key = lambda node: json.loads(node.node.metadata["obj_json"])[self.field_name]
+        return self._get_sort_func()(self.top_n, nodes, key=sort_key)
+
+    def _get_sort_func(self):
+        return heapq.nlargest if self.order == "desc" else heapq.nsmallest
+
+    def _check_metadata(self, node: ObjectNode):
+        try:
+            obj_dict = json.loads(node.metadata.get("obj_json"))
+        except Exception as e:
+            raise ValueError(f"Invalid object json in metadata: {node.metadata}, error: {e}")
+
+        if self.field_name not in obj_dict:
+            raise ValueError(f"Field '{self.field_name}' not found in object: {obj_dict}")

metagpt/rag/schema.py

@@ -101,6 +101,11 @@ class ColbertRerankConfig(BaseRankerConfig):
     keep_retrieval_score: bool = Field(default=False, description="Whether to keep the retrieval score in metadata.")
 
 
+class ObjectRankerConfig(BaseRankerConfig):
+    field_name: str = Field(..., description="field name of the object, field's value must can be compared.")
+    order: Literal["desc", "asc"] = Field(default="desc", description="the direction of order.")
+
+
 class BaseIndexConfig(BaseModel):
     """Common config for index.