Files
hyungi_document_server/app/services/search/retrieval_service.py
Hyungi Ahn 2ca67dacea feat(search): Phase 1.2-G hybrid retrieval (doc + chunks)
Phase 1.2-C 평가셋: chunks-only Recall 0.788 → 0.660 catastrophic.
ivfflat probes 1 → 10 → 20 진단 결과 잔여 차이는 chunks vs docs embedding의
본질적 차이 (segment 매칭 vs 전체 본문 평균).

해결: doc + chunks hybrid retrieval (정석).

신규 구조:
- search_vector(): 두 SQL을 asyncio.gather로 병렬 호출
- _search_vector_docs(): documents.embedding cosine top N (recall robust)
- _search_vector_chunks(): document_chunks.embedding window partition
  (doc당 top 2 chunks, ivfflat top inner_k 후 ROW_NUMBER PARTITION)
- _merge_doc_and_chunk_vectors(): 가중치 + dedup
  - chunk score * 1.2 (segment 매칭 더 정확)
  - doc score * 1.0 (recall 보완)
  - doc_id 기준 dedup, chunks 우선

데이터 흐름:
  1. query embedding 1번 (bge-m3)
  2. asyncio.gather([_docs_call(), _chunks_call()])
  3. _merge_doc_and_chunk_vectors → list[SearchResult]
  4. compress_chunks_to_docs (그대로 사용)
  5. fusion (그대로)
  6. (Phase 1.3) chunks_by_doc 회수 → reranker

검증 게이트 (회복 목표):
- Recall@10 ≥ 0.75 (baseline 0.788 - 0.04 이내)
- unique_docs per query ≥ 8
- natural_language_ko Recall ≥ 0.65
- latency p95 < 250ms
2026-04-08 13:02:23 +09:00

343 lines
14 KiB
Python

"""검색 후보 수집 서비스 (Phase 1.2).
text(documents FTS + trigram) + vector(documents.embedding + chunks.embedding hybrid) 후보를
SearchResult 리스트로 반환.
Phase 1.1a: search.py의 _search_text/_search_vector를 이전 (ILIKE 그대로).
Phase 1.2-B: ILIKE → trigram `%` + `similarity()`. ILIKE 풀 스캔 제거.
Phase 1.2-C: vector retrieval을 document_chunks 테이블로 전환 → catastrophic recall 손실.
Phase 1.2-G: doc + chunks hybrid retrieval 보강.
- documents.embedding (recall robust, 자연어 매칭 강함)
- document_chunks.embedding (precision, segment 매칭)
- 두 SQL 동시 호출 후 doc_id 기준 merge (chunk 가중치 1.2, doc 1.0)
"""
from __future__ import annotations
import asyncio
from typing import TYPE_CHECKING
from sqlalchemy import text
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
from ai.client import AIClient
from core.database import engine
if TYPE_CHECKING:
from api.search import SearchResult
# Hybrid merge 가중치 (1.2-G)
DOC_VECTOR_WEIGHT = 1.0
CHUNK_VECTOR_WEIGHT = 1.2
async def search_text(
session: AsyncSession, query: str, limit: int
) -> list["SearchResult"]:
"""FTS + trigram 필드별 가중치 검색 (Phase 1.2-B UNION 분해).
Phase 1.2-B 진단:
OR로 묶은 단일 SELECT는 PostgreSQL planner가 OR 결합 인덱스를 못 만들고
Seq Scan을 선택 (small table 765 docs). EXPLAIN으로 측정 시 525ms.
→ CTE + UNION으로 분해하면 각 branch가 자기 인덱스 활용 → 26ms (95% 감소).
구조:
candidates CTE
├─ title % → idx_documents_title_trgm
├─ ai_summary % → idx_documents_ai_summary_trgm
│ (length > 0 partial index 매치 조건 포함)
└─ FTS @@ plainto_tsquery → idx_documents_fts_full
JOIN documents d ON d.id = c.id
ORDER BY 5컬럼 similarity 가중 합산 + ts_rank * 2.0
가중치: title 3.0 / ai_tags 2.5 / user_note 2.0 / ai_summary 1.5 / extracted_text 1.0
threshold:
pg_trgm.similarity_threshold default = 0.3
→ multi-token 한국어 뉴스 쿼리(예: "이란 미국 전쟁 글로벌 반응")에서
candidates를 못 모음 → recall 감소 (0.788 → 0.750)
→ set_limit(0.15)으로 낮춰 recall 회복. precision은 ORDER BY similarity 합산이 보정.
"""
from api.search import SearchResult # 순환 import 회피
# trigram threshold를 0.15로 낮춰 multi-token query recall 회복
# SQLAlchemy async session 내 두 execute는 같은 connection 사용
await session.execute(text("SELECT set_limit(0.15)"))
result = await session.execute(
text("""
WITH candidates AS (
-- title trigram (idx_documents_title_trgm)
SELECT id FROM documents
WHERE deleted_at IS NULL AND title % :q
UNION
-- ai_summary trigram (idx_documents_ai_summary_trgm 부분 인덱스 매치)
SELECT id FROM documents
WHERE deleted_at IS NULL
AND ai_summary IS NOT NULL
AND length(ai_summary) > 0
AND ai_summary % :q
UNION
-- FTS 통합 인덱스 (idx_documents_fts_full)
SELECT id FROM documents
WHERE deleted_at IS NULL
AND to_tsvector('simple',
coalesce(title, '') || ' ' ||
coalesce(ai_tags::text, '') || ' ' ||
coalesce(ai_summary, '') || ' ' ||
coalesce(user_note, '') || ' ' ||
coalesce(extracted_text, '')
) @@ plainto_tsquery('simple', :q)
)
SELECT d.id, d.title, d.ai_domain, d.ai_summary, d.file_format,
left(d.extracted_text, 200) AS snippet,
(
-- 컬럼별 trigram similarity 가중 합산
similarity(coalesce(d.title, ''), :q) * 3.0
+ similarity(coalesce(d.ai_tags::text, ''), :q) * 2.5
+ similarity(coalesce(d.user_note, ''), :q) * 2.0
+ similarity(coalesce(d.ai_summary, ''), :q) * 1.5
+ similarity(coalesce(d.extracted_text, ''), :q) * 1.0
-- FTS 보너스 (idx_documents_fts_full 활용)
+ coalesce(ts_rank(
to_tsvector('simple',
coalesce(d.title, '') || ' ' ||
coalesce(d.ai_tags::text, '') || ' ' ||
coalesce(d.ai_summary, '') || ' ' ||
coalesce(d.user_note, '') || ' ' ||
coalesce(d.extracted_text, '')
),
plainto_tsquery('simple', :q)
), 0) * 2.0
) AS score,
-- match_reason: similarity 가장 큰 컬럼 또는 FTS
CASE
WHEN similarity(coalesce(d.title, ''), :q) >= 0.3 THEN 'title'
WHEN similarity(coalesce(d.ai_tags::text, ''), :q) >= 0.3 THEN 'tags'
WHEN similarity(coalesce(d.user_note, ''), :q) >= 0.3 THEN 'note'
WHEN similarity(coalesce(d.ai_summary, ''), :q) >= 0.3 THEN 'summary'
WHEN similarity(coalesce(d.extracted_text, ''), :q) >= 0.3 THEN 'content'
ELSE 'fts'
END AS match_reason
FROM documents d
JOIN candidates c ON d.id = c.id
ORDER BY score DESC
LIMIT :limit
"""),
{"q": query, "limit": limit},
)
return [SearchResult(**row._mapping) for row in result]
async def search_vector(
session: AsyncSession, query: str, limit: int
) -> list["SearchResult"]:
"""Hybrid 벡터 검색 — doc + chunks 동시 retrieval (Phase 1.2-G).
Phase 1.2-C 진단:
chunks-only는 segment 의미 손실로 자연어 query에서 catastrophic recall.
doc embedding은 전체 본문 평균 → recall robust.
→ 두 retrieval 동시 사용이 정석.
데이터 흐름:
1. query embedding 1번 (bge-m3)
2. asyncio.gather로 두 SQL 동시 호출:
- _search_vector_docs: documents.embedding cosine top N
- _search_vector_chunks: document_chunks.embedding window partition (doc당 top 2)
3. _merge_doc_and_chunk_vectors로 가중치 + dedup:
- chunk score * 1.2 (precision)
- doc score * 1.0 (recall)
- doc_id 기준 dedup, chunks 우선
Returns:
list[SearchResult] — doc_id 중복 제거됨. compress_chunks_to_docs는 그대로 동작.
chunks_by_doc은 search.py에서 group_by_doc으로 보존.
"""
try:
client = AIClient()
query_embedding = await client.embed(query)
await client.close()
except Exception:
return []
embedding_str = str(query_embedding)
# 두 SQL 병렬 호출 — 각각 별도 session 사용 (asyncpg connection은 statement 단위 직렬)
Session = async_sessionmaker(engine)
async def _docs_call() -> list["SearchResult"]:
async with Session() as s:
return await _search_vector_docs(s, embedding_str, limit * 4)
async def _chunks_call() -> list["SearchResult"]:
async with Session() as s:
return await _search_vector_chunks(s, embedding_str, limit * 4)
doc_results, chunk_results = await asyncio.gather(_docs_call(), _chunks_call())
return _merge_doc_and_chunk_vectors(doc_results, chunk_results)
async def _search_vector_docs(
session: AsyncSession, embedding_str: str, limit: int
) -> list["SearchResult"]:
"""documents.embedding 직접 검색 — recall robust (자연어 매칭).
chunks가 없는 doc도 매칭 가능. score는 cosine similarity (1 - distance).
chunk_id/chunk_index/section_title은 None.
"""
from api.search import SearchResult # 순환 import 회피
result = await session.execute(
text("""
SELECT
id,
title,
ai_domain,
ai_summary,
file_format,
(1 - (embedding <=> cast(:embedding AS vector))) AS score,
left(extracted_text, 200) AS snippet,
'vector_doc' AS match_reason,
NULL::bigint AS chunk_id,
NULL::integer AS chunk_index,
NULL::text AS section_title
FROM documents
WHERE embedding IS NOT NULL AND deleted_at IS NULL
ORDER BY embedding <=> cast(:embedding AS vector)
LIMIT :limit
"""),
{"embedding": embedding_str, "limit": limit},
)
return [SearchResult(**row._mapping) for row in result]
async def _search_vector_chunks(
session: AsyncSession, embedding_str: str, limit: int
) -> list["SearchResult"]:
"""document_chunks.embedding 검색 + window partition (doc당 top 2 chunks).
SQL 흐름:
1. inner CTE topk: ivfflat 인덱스로 top-K chunks 추출
2. ranked CTE: doc_id PARTITION + ROW_NUMBER (score 내림차순)
3. outer: rn <= 2 (doc당 max 2 chunks) + JOIN documents
"""
from api.search import SearchResult # 순환 import 회피
inner_k = max(limit * 5, 500)
result = await session.execute(
text("""
WITH topk AS (
SELECT
c.id AS chunk_id,
c.doc_id,
c.chunk_index,
c.section_title,
c.text,
c.embedding <=> cast(:embedding AS vector) AS dist
FROM document_chunks c
WHERE c.embedding IS NOT NULL
ORDER BY c.embedding <=> cast(:embedding AS vector)
LIMIT :inner_k
),
ranked AS (
SELECT
chunk_id, doc_id, chunk_index, section_title, text, dist,
ROW_NUMBER() OVER (PARTITION BY doc_id ORDER BY dist ASC) AS rn
FROM topk
)
SELECT
d.id AS id,
d.title AS title,
d.ai_domain AS ai_domain,
d.ai_summary AS ai_summary,
d.file_format AS file_format,
(1 - r.dist) AS score,
left(r.text, 200) AS snippet,
'vector_chunk' AS match_reason,
r.chunk_id AS chunk_id,
r.chunk_index AS chunk_index,
r.section_title AS section_title
FROM ranked r
JOIN documents d ON d.id = r.doc_id
WHERE r.rn <= 2 AND d.deleted_at IS NULL
ORDER BY r.dist
LIMIT :limit
"""),
{"embedding": embedding_str, "inner_k": inner_k, "limit": limit},
)
return [SearchResult(**row._mapping) for row in result]
def _merge_doc_and_chunk_vectors(
doc_results: list["SearchResult"],
chunk_results: list["SearchResult"],
) -> list["SearchResult"]:
"""doc + chunks vector 결과 merge (Phase 1.2-G).
가중치:
- chunk score * 1.2 (segment 매칭이 더 정확)
- doc score * 1.0 (전체 본문 평균, recall 보완)
Dedup:
- doc_id 기준
- chunks가 있으면 chunks 우선 (segment 정보 + chunk_id 보존)
- chunks에 없는 doc은 doc-wrap으로 추가
Returns:
score 내림차순 정렬된 SearchResult 리스트.
chunk_id가 None이면 doc-wrap 결과(text-only 매치 doc 처리에 사용).
"""
by_doc_id: dict[int, "SearchResult"] = {}
# chunks 먼저 (가중치 적용 + chunk_id 보존)
for c in chunk_results:
c.score = c.score * CHUNK_VECTOR_WEIGHT
prev = by_doc_id.get(c.id)
if prev is None or c.score > prev.score:
by_doc_id[c.id] = c
# doc 매치는 chunks에 없는 doc만 추가 (chunks 우선 원칙)
for d in doc_results:
d.score = d.score * DOC_VECTOR_WEIGHT
if d.id not in by_doc_id:
by_doc_id[d.id] = d
# score 내림차순 정렬
return sorted(by_doc_id.values(), key=lambda r: r.score, reverse=True)
def compress_chunks_to_docs(
chunks: list["SearchResult"], limit: int
) -> tuple[list["SearchResult"], dict[int, list["SearchResult"]]]:
"""chunk-level 결과를 doc-level로 압축하면서 raw chunks를 보존.
fusion은 doc 기준이어야 하지만(같은 doc 중복 방지), Phase 1.3 reranker는
chunk 기준 raw 데이터가 필요함. 따라서 압축본과 raw를 동시 반환.
압축 규칙:
- doc_id 별로 가장 score 높은 chunk만 doc_results에 추가
- 같은 doc의 다른 chunks는 chunks_by_doc dict에 보존 (Phase 1.3 reranker용)
- score 내림차순 정렬 후 limit개만 doc_results
Returns:
(doc_results, chunks_by_doc)
- doc_results: list[SearchResult] — doc당 best chunk score, fusion 입력
- chunks_by_doc: dict[doc_id, list[SearchResult]] — 모든 raw chunks 보존
"""
if not chunks:
return [], {}
chunks_by_doc: dict[int, list["SearchResult"]] = {}
best_per_doc: dict[int, "SearchResult"] = {}
for chunk in chunks:
chunks_by_doc.setdefault(chunk.id, []).append(chunk)
prev_best = best_per_doc.get(chunk.id)
if prev_best is None or chunk.score > prev_best.score:
best_per_doc[chunk.id] = chunk
# doc 단위 best score 정렬, 상위 limit개
doc_results = sorted(best_per_doc.values(), key=lambda r: r.score, reverse=True)
return doc_results[:limit], chunks_by_doc