feat: add streaming learning assistant and knowledge base scaffolding
This commit is contained in:
刘金宝
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import json
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import time
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from collections.abc import AsyncIterator
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from dataclasses import dataclass
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from sqlalchemy.orm import Session
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from app.agents.learning_assistant_agent import LearningAssistantAgent
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from app.core.config import settings
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from app.core.context import UserContext
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from app.core.exceptions import AppError
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from app.repositories.knowledge_base_repository import KnowledgeBaseRepository
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from app.schemas.learning_assistant import LearningAssistantChatRequest, LearningAssistantChatResponse, LearningAssistantSource
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from app.services.knowledge_space_service import KnowledgeSpaceService
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from app.services.vector_search_service import RetrievedChunk, VectorSearchService
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@dataclass(frozen=True)
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class LearningAssistantRetrieval:
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"""学习助手检索结果：封装知识库命中、耗时和降级原因。"""
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institution_id: int | None
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score_threshold: float
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sources: list[LearningAssistantSource]
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embedding_latency_ms: int | None = None
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search_latency_ms: int | None = None
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retrieval_error: str | None = None
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class LearningAssistantService:
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"""AI 学习助手服务：优先 RAG 检索，知识库不可用时降级为通用流式问答。"""
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def __init__(
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self,
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db: Session,
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*,
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vector_search_service: VectorSearchService | None = None,
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agent: LearningAssistantAgent | None = None,
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) -> None:
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self.db = db
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self.repo = KnowledgeBaseRepository(db)
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self.space_service = KnowledgeSpaceService(self.repo)
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self.vector_search = vector_search_service or VectorSearchService(db)
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self.agent = agent or LearningAssistantAgent()
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async def chat(self, ctx: UserContext, payload: LearningAssistantChatRequest) -> LearningAssistantChatResponse:
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"""知识问答调试：检索失败不阻断回答，返回完整文本和检索降级信息。"""
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start = time.perf_counter()
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retrieval = await self._retrieve_sources(ctx, payload)
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llm_started = time.perf_counter()
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response = await self.agent.answer(payload.question, retrieval.sources)
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total_latency_ms = int((time.perf_counter() - start) * 1000)
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llm_latency_ms = response.latency_ms or int((time.perf_counter() - llm_started) * 1000)
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self._write_query_log(
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ctx=ctx,
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payload=payload,
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retrieval=retrieval,
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answer=response.content,
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model=response.model,
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llm_latency_ms=llm_latency_ms,
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total_latency_ms=total_latency_ms,
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)
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return LearningAssistantChatResponse(
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answer=response.content,
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retrieval_hit=bool(retrieval.sources),
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sources=retrieval.sources,
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retrieval_error=retrieval.retrieval_error,
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model=response.model,
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embedding_latency_ms=retrieval.embedding_latency_ms,
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search_latency_ms=retrieval.search_latency_ms,
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llm_latency_ms=llm_latency_ms,
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total_latency_ms=total_latency_ms,
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)
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async def stream_chat(self, ctx: UserContext, payload: LearningAssistantChatRequest) -> AsyncIterator[str]:
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"""流式知识问答：先返回检索状态，再流式输出 LLM 回答。"""
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start = time.perf_counter()
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retrieval = await self._retrieve_sources(ctx, payload)
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yield self._sse(
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"retrieval_done",
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{
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"retrieval_hit": bool(retrieval.sources),
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"sources": [source.model_dump() for source in retrieval.sources],
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"retrieval_error": retrieval.retrieval_error,
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"embedding_latency_ms": retrieval.embedding_latency_ms,
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"search_latency_ms": retrieval.search_latency_ms,
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},
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)
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answer_parts: list[str] = []
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llm_latency_ms: int | None = None
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model: str | None = None
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try:
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async for chunk in self.agent.stream_answer(payload.question, retrieval.sources):
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if chunk.done:
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llm_latency_ms = chunk.total_latency_ms
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model = chunk.model
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break
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if chunk.delta:
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answer_parts.append(chunk.delta)
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yield self._sse("answer_delta", {"delta": chunk.delta})
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except AppError as exc:
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yield self._sse("error", {"code": exc.code, "message": exc.message})
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return
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except Exception:
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yield self._sse("error", {"code": "LEARNING_ASSISTANT_LLM_FAILED", "message": "AI 学习助手回答生成失败，请稍后重试"})
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return
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answer = "".join(answer_parts)
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total_latency_ms = int((time.perf_counter() - start) * 1000)
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self._write_query_log(
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ctx=ctx,
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payload=payload,
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retrieval=retrieval,
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answer=answer,
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model=model,
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llm_latency_ms=llm_latency_ms,
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total_latency_ms=total_latency_ms,
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commit=True,
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)
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yield self._sse("answer_done", {"model": model, "total_latency_ms": total_latency_ms})
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async def _retrieve_sources(self, ctx: UserContext, payload: LearningAssistantChatRequest) -> LearningAssistantRetrieval:
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"""知识检索：按机构读取知识空间；无空间、Milvus 或 embedding 异常时降级为空来源。"""
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score_threshold = payload.score_threshold if payload.score_threshold is not None else settings.rag_score_threshold
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try:
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institution_id = self.space_service.require_institution_id(ctx)
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except AppError:
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return LearningAssistantRetrieval(
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institution_id=None,
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score_threshold=score_threshold,
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sources=[],
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retrieval_error="当前用户缺少机构信息，已转为大模型通用学习回答。",
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)
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try:
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space = self.space_service.get_active_space(ctx)
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retrieval = await self.vector_search.search(
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institution_id=space.institution_id,
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collection_name=space.collection_name,
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question=payload.question,
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top_k=payload.top_k,
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score_threshold=payload.score_threshold,
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)
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return LearningAssistantRetrieval(
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institution_id=space.institution_id,
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score_threshold=payload.score_threshold if payload.score_threshold is not None else space.score_threshold,
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sources=self._build_sources(retrieval.chunks),
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embedding_latency_ms=retrieval.embedding_latency_ms,
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search_latency_ms=retrieval.search_latency_ms,
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)
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except AppError as exc:
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if exc.code in {"KNOWLEDGE_SPACE_NOT_FOUND", "MILVUS_COLLECTION_NOT_FOUND", "EMBEDDING_CALL_FAILED"}:
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return LearningAssistantRetrieval(
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institution_id=institution_id,
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score_threshold=score_threshold,
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sources=[],
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retrieval_error="当前机构知识库暂未初始化或检索不可用，已转为大模型通用学习回答。",
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)
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raise
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except Exception:
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return LearningAssistantRetrieval(
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institution_id=institution_id,
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score_threshold=score_threshold,
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sources=[],
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retrieval_error="当前机构知识库检索暂不可用，已转为大模型通用学习回答。",
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)
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def _write_query_log(
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self,
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*,
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ctx: UserContext,
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payload: LearningAssistantChatRequest,
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retrieval: LearningAssistantRetrieval,
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answer: str,
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model: str | None,
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llm_latency_ms: int | None,
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total_latency_ms: int | None,
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commit: bool = False,
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) -> None:
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"""查询日志：仅在存在机构 ID 时记录 RAG 命中、来源和耗时。"""
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if retrieval.institution_id is None:
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return
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self.repo.create_query_log(
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user_id=ctx.user_id,
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institution_id=retrieval.institution_id,
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question=payload.question,
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retrieval_hit=bool(retrieval.sources),
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retrieved_chunk_ids=[source.chunk_uid for source in retrieval.sources],
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answer_summary=answer,
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llm_model=model,
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top_k=payload.top_k or len(retrieval.sources) or settings.rag_top_k,
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score_threshold=retrieval.score_threshold,
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embedding_latency_ms=retrieval.embedding_latency_ms,
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search_latency_ms=retrieval.search_latency_ms,
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llm_latency_ms=llm_latency_ms,
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total_latency_ms=total_latency_ms,
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)
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if commit:
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self.db.commit()
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def _build_sources(self, chunks: list[RetrievedChunk]) -> list[LearningAssistantSource]:
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"""来源构建：把检索分片转换为前端可展示的 PDF 来源结构。"""
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sources: list[LearningAssistantSource] = []
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for item in chunks:
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document = self.repo.get_document(item.chunk.document_id, item.chunk.institution_id)
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quote = item.chunk.chunk_text[:500]
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sources.append(
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LearningAssistantSource(
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document_id=item.chunk.document_id,
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document_title=document.document_title if document else None,
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file_name=document.file_name if document else "",
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page_start=item.chunk.page_start,
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page_end=item.chunk.page_end,
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chunk_uid=item.chunk.chunk_uid,
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score=round(item.score, 4),
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quote=quote,
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)
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)
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return sources
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def _sse(self, event: str, data: dict) -> str:
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"""SSE 封装：统一输出 event + data 格式。"""
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return f"event: {event}\ndata: {json.dumps(data, ensure_ascii=False)}\n\n"
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