faiss_rag_enterprise/llama_index/postprocessor/node_recency.py

"""Node recency post-processor."""
from datetime import datetime
from typing import List, Optional, Set

import numpy as np
import pandas as pd

from llama_index.bridge.pydantic import Field
from llama_index.postprocessor.types import BaseNodePostprocessor
from llama_index.schema import MetadataMode, NodeWithScore, QueryBundle
from llama_index.service_context import ServiceContext

# NOTE: currently not being used
# DEFAULT_INFER_RECENCY_TMPL = (
#     "A question is provided.\n"
#     "The goal is to determine whether the question requires finding the most recent "
#     "context.\n"
#     "Please respond with YES or NO.\n"
#     "Question: What is the current status of the patient?\n"
#     "Answer: YES\n"
#     "Question: What happened in the Battle of Yorktown?\n"
#     "Answer: NO\n"
#     "Question: What are the most recent changes to the project?\n"
#     "Answer: YES\n"
#     "Question: How did Harry defeat Voldemort in the Battle of Hogwarts?\n"
#     "Answer: NO\n"
#     "Question: {query_str}\n"
#     "Answer: "
# )


# def parse_recency_pred(pred: str) -> bool:
#     """Parse recency prediction."""
#     if "YES" in pred:
#         return True
#     elif "NO" in pred:
#         return False
#     else:
#         raise ValueError(f"Invalid recency prediction: {pred}.")


class FixedRecencyPostprocessor(BaseNodePostprocessor):
    """Recency post-processor.

    This post-processor does the following steps:

    - Decides if we need to use the post-processor given the query
      (is it temporal-related?)
    - If yes, sorts nodes by date.
    - Take the first k nodes (by default 1), and use that to synthesize an answer.

    """

    service_context: ServiceContext
    top_k: int = 1
    # infer_recency_tmpl: str = Field(default=DEFAULT_INFER_RECENCY_TMPL)
    date_key: str = "date"

    @classmethod
    def class_name(cls) -> str:
        return "FixedRecencyPostprocessor"

    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.")

        # sort nodes by date
        node_dates = pd.to_datetime(
            [node.node.metadata[self.date_key] for node in nodes]
        )
        sorted_node_idxs = np.flip(node_dates.argsort())
        sorted_nodes = [nodes[idx] for idx in sorted_node_idxs]

        return sorted_nodes[: self.top_k]


DEFAULT_QUERY_EMBEDDING_TMPL = (
    "The current document is provided.\n"
    "----------------\n"
    "{context_str}\n"
    "----------------\n"
    "Given the document, we wish to find documents that contain \n"
    "similar context. Note that these documents are older "
    "than the current document, meaning that certain details may be changed. \n"
    "However, the high-level context should be similar.\n"
)


class EmbeddingRecencyPostprocessor(BaseNodePostprocessor):
    """Recency post-processor.

    This post-processor does the following steps:

    - Decides if we need to use the post-processor given the query
      (is it temporal-related?)
    - If yes, sorts nodes by date.
    - For each node, look at subsequent nodes and filter out nodes
      that have high embedding similarity with the current node.
      Because this means the subsequent node may have overlapping content
      with the current node but is also out of date
    """

    service_context: ServiceContext
    # infer_recency_tmpl: str = Field(default=DEFAULT_INFER_RECENCY_TMPL)
    date_key: str = "date"
    similarity_cutoff: float = Field(default=0.7)
    query_embedding_tmpl: str = Field(default=DEFAULT_QUERY_EMBEDDING_TMPL)

    @classmethod
    def class_name(cls) -> str:
        return "EmbeddingRecencyPostprocessor"

    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.")

        # sort nodes by date
        node_dates = pd.to_datetime(
            [node.node.metadata[self.date_key] for node in nodes]
        )
        sorted_node_idxs = np.flip(node_dates.argsort())
        sorted_nodes: List[NodeWithScore] = [nodes[idx] for idx in sorted_node_idxs]

        # get embeddings for each node
        embed_model = self.service_context.embed_model
        texts = [node.get_content(metadata_mode=MetadataMode.EMBED) for node in nodes]
        text_embeddings = embed_model.get_text_embedding_batch(texts=texts)

        node_ids_to_skip: Set[str] = set()
        for idx, node in enumerate(sorted_nodes):
            if node.node.node_id in node_ids_to_skip:
                continue
            # get query embedding for the "query" node
            # NOTE: not the same as the text embedding because
            # we want to optimize for retrieval results

            query_text = self.query_embedding_tmpl.format(
                context_str=node.node.get_content(metadata_mode=MetadataMode.EMBED),
            )
            query_embedding = embed_model.get_query_embedding(query_text)

            for idx2 in range(idx + 1, len(sorted_nodes)):
                if sorted_nodes[idx2].node.node_id in node_ids_to_skip:
                    continue
                node2 = sorted_nodes[idx2]
                if (
                    np.dot(query_embedding, text_embeddings[idx2])
                    > self.similarity_cutoff
                ):
                    node_ids_to_skip.add(node2.node.node_id)

        return [
            node for node in sorted_nodes if node.node.node_id not in node_ids_to_skip
        ]


class TimeWeightedPostprocessor(BaseNodePostprocessor):
    """Time-weighted post-processor.

    Reranks a set of nodes based on their recency.

    """

    time_decay: float = Field(default=0.99)
    last_accessed_key: str = "__last_accessed__"
    time_access_refresh: bool = True
    # optionally set now (makes it easier to test)
    now: Optional[float] = None
    top_k: int = 1

    @classmethod
    def class_name(cls) -> str:
        return "TimeWeightedPostprocessor"

    def _postprocess_nodes(
        self,
        nodes: List[NodeWithScore],
        query_bundle: Optional[QueryBundle] = None,
    ) -> List[NodeWithScore]:
        """Postprocess nodes."""
        now = self.now or datetime.now().timestamp()
        # TODO: refactor with get_top_k_embeddings

        similarities = []
        for node_with_score in nodes:
            # embedding similarity score
            score = node_with_score.score or 1.0
            node = node_with_score.node
            # time score
            if node.metadata is None:
                raise ValueError("metadata is None")

            last_accessed = node.metadata.get(self.last_accessed_key, None)
            if last_accessed is None:
                last_accessed = now

            hours_passed = (now - last_accessed) / 3600
            time_similarity = (1 - self.time_decay) ** hours_passed

            similarity = score + time_similarity

            similarities.append(similarity)

        sorted_tups = sorted(zip(similarities, nodes), key=lambda x: x[0], reverse=True)

        top_k = min(self.top_k, len(sorted_tups))
        result_tups = sorted_tups[:top_k]
        result_nodes = [
            NodeWithScore(node=n.node, score=score) for score, n in result_tups
        ]

        # set __last_accessed__ to now
        if self.time_access_refresh:
            for node_with_score in result_nodes:
                node_with_score.node.metadata[self.last_accessed_key] = now

        return result_nodes