prevnext.py

from llama_index.vector_stores.qdrant import QdrantVectorStore

def get_forward_nodes(
    node_with_score: NodeWithScore, num_nodes: int, vector_store: QdrantVectorStore
) -> Dict[str, NodeWithScore]:
    """Get forward nodes."""
    node = node_with_score.node
    nodes: Dict[str, NodeWithScore] = {node.node_id: node_with_score}
    cur_count = 0
    # get forward nodes in an iterative manner
    while cur_count < num_nodes:
        if NodeRelationship.NEXT not in node.relationships:
            break

        next_node_info = node.next_node
        if next_node_info is None:
            break

        next_node_id = next_node_info.node_id
        next_node = vector_store.get_nodes(next_node_id)[0]
        nodes[next_node.node_id] = NodeWithScore(node=next_node)
        node = next_node
        cur_count += 1
    return nodes


def get_backward_nodes(
    node_with_score: NodeWithScore, num_nodes: int, vector_store: QdrantVectorStore
) -> Dict[str, NodeWithScore]:
    """Get backward nodes."""
    node = node_with_score.node
    # get backward nodes in an iterative manner
    nodes: Dict[str, NodeWithScore] = {node.node_id: node_with_score}
    cur_count = 0
    while cur_count < num_nodes:
        prev_node_info = node.prev_node
        if prev_node_info is None:
            break
        prev_node_id = prev_node_info.node_id
        prev_node = vector_store.get_nodes(prev_node_id)[0]
        if prev_node is None:
            break
        nodes[prev_node.node_id] = NodeWithScore(node=prev_node)
        node = prev_node
        cur_count += 1
    return nodes


class VectorPrevNextNodePostprocessor(BaseNodePostprocessor):
    vector_store: QdrantVectorStore
    mode: str = Field(default="next")

    @validator("mode")
    def _validate_mode(cls, v: str) -> str:
        """Validate mode."""
        if v not in ["next", "previous", "both"]:
            raise ValueError(f"Invalid mode: {v}")
        return v

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

    def _postprocess_nodes(
        self,
        nodes: List[NodeWithScore],
        query_bundle: Optional[QueryBundle] = None,
    ) -> List[NodeWithScore]:
        """Postprocess nodes."""
        all_nodes: Dict[str, NodeWithScore] = {}
        for node in nodes:
            all_nodes[node.node.node_id] = node
            if self.mode == "next":
                all_nodes.update(get_forward_nodes(node, self.num_nodes, self.vector_store))
            elif self.mode == "previous":
                all_nodes.update(
                    get_backward_nodes(node, self.num_nodes, self.vector_store)
                )
            elif self.mode == "both":
                all_nodes.update(get_forward_nodes(node, self.num_nodes, self.vector_store))
                all_nodes.update(
                    get_backward_nodes(node, self.num_nodes, self.vector_store)
                )
            else:
                raise ValueError(f"Invalid mode: {self.mode}")

        all_nodes_values: List[NodeWithScore] = list(all_nodes.values())
        sorted_nodes: List[NodeWithScore] = []
        for node in all_nodes_values:
            # variable to check if cand node is inserted
            node_inserted = False
            for i, cand in enumerate(sorted_nodes):
                node_id = node.node.node_id
                # prepend to current candidate
                prev_node_info = cand.node.prev_node
                next_node_info = cand.node.next_node
                if prev_node_info is not None and node_id == prev_node_info.node_id:
                    node_inserted = True
                    sorted_nodes.insert(i, node)
                    break
                # append to current candidate
                elif next_node_info is not None and node_id == next_node_info.node_id:
                    node_inserted = True
                    sorted_nodes.insert(i + 1, node)
                    break

            if not node_inserted:
                sorted_nodes.append(node)

        return sorted_nodes

Btw, can you please also post your solution in the llama-index issue?

Yes sure thanks.