feat(study): 이론↔문제 브리지 (Stage B) — 개념별 정답률·약점 개념 지도

이론공부 B→A→C 의 B. 완성된 문제풀이에 이론 연결(약점 구동).
- 마이그 382 study_concept_links(개념 doc↔기출, FK 없음) + 백필 SQL(임베딩 코사인 top-k=10·threshold 0.62 → 2362링크·284개념·964문항)
- concept_links 서비스(related_questions·weakness_map 롤업) + GET /concepts/{id}/questions·/concepts/weakness-map(라우트 순서=weakness-map 먼저)
- 리더 관련기출 섹션(정답률·문항 stub→문항상세) + 홈 약점개념 위젯
- 적대리뷰 반영: Promise.all 격리(weakness-map 실패→코어 대시보드 블랙아웃 방지)·q.subject null 폴백. 백필=배포 후 트랜잭션 래핑 실행. 문제풀이 무접촉

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/api/study_concepts.py

@@ -15,6 +15,7 @@ from core.auth import get_current_user
 from core.database import get_session
 from models.user import User
 from services.study import concept_curriculum as cc
+from services.study import concept_links as cl
 
 router = APIRouter()
 
@@ -43,6 +44,20 @@ async def get_today_concepts(
     return await cc.today_concepts(session, user.id, topic_id, limit)
 
 
+@router.get("/concepts/weakness-map")
+async def get_weakness_map(
+    user: Annotated[User, Depends(get_current_user)],
+    session: Annotated[AsyncSession, Depends(get_session)],
+    topic_id: int = DEFAULT_TOPIC_ID,
+    limit: int = 12,
+):
+    """개념 약점 지도 — 링크된 기출 정답률로 약점 개념(정답률<60%) 우선(이론↔문제)."""
+    name = await cc._topic_name(session, topic_id)
+    if not name:
+        return {"weak": [], "weak_total": 0, "evaluated_total": 0}
+    return await cl.weakness_map(session, user.id, name, limit)
+
+
 @router.get("/concepts/{doc_id}")
 async def get_concept_detail(
     doc_id: int,
@@ -57,6 +72,17 @@ async def get_concept_detail(
     return detail
 
 
+@router.get("/concepts/{doc_id}/questions")
+async def get_concept_questions(
+    doc_id: int,
+    user: Annotated[User, Depends(get_current_user)],
+    session: Annotated[AsyncSession, Depends(get_session)],
+    limit: int = 20,
+):
+    """개념 관련 기출 + 내 정답률 (이론↔문제 브리지)."""
+    return await cl.related_questions(session, user.id, doc_id, limit)
+
+
 @router.post("/concepts/{doc_id}/read")
 async def post_concept_read(
     doc_id: int,

app/services/study/concept_links.py

@@ -0,0 +1,139 @@
+"""concept_links — 이론↔문제 브리지 롤업 (Stage B).
+
+study_concept_links(개념 doc ↔ 기출문항, 임베딩 코사인) + study_question_progress(내 풀이상태)를
+조인해 (a) 개념별 관련 기출 + 내 정답률(related_questions), (b) 개념 약점 지도(weakness_map) 산출.
+읽기 전용 집계 · LLM 0. 링크 적재는 scripts/concept_links_backfill.sql(임베딩) 배치.
+정답률 = 링크된 문항 중 progress.last_outcome 기준(attempted=풀이이력 보유, correct=최근정답).
+"""
+
+from __future__ import annotations
+
+from sqlalchemy import text
+from sqlalchemy.ext.asyncio import AsyncSession
+
+_ACCURACY_WEAK_PCT = 60  # 정답률 < 60% = 약점(attempted>0 일 때만)
+
+_AGG_SQL = text(
+    """
+    SELECT count(*) AS linked,
+           count(pr.study_question_id) FILTER (WHERE pr.last_outcome IS NOT NULL) AS attempted,
+           count(*) FILTER (WHERE pr.last_outcome = 'correct') AS correct
+    FROM study_concept_links l
+    LEFT JOIN study_question_progress pr
+      ON pr.study_question_id = l.question_id AND pr.user_id = :uid
+    WHERE l.concept_doc_id = :doc_id AND l.link_source = 'embedding'
+    """
+)
+
+_QROWS_SQL = text(
+    """
+    SELECT q.id AS id, q.subject AS subject, q.exam_round AS exam_round,
+           q.exam_question_number AS qnum, l.score AS score,
+           pr.last_outcome AS last_outcome, pr.review_stage AS review_stage
+    FROM study_concept_links l
+    JOIN study_questions q ON q.id = l.question_id AND q.deleted_at IS NULL AND q.is_active
+    LEFT JOIN study_question_progress pr
+      ON pr.study_question_id = q.id AND pr.user_id = :uid
+    WHERE l.concept_doc_id = :doc_id AND l.link_source = 'embedding'
+    ORDER BY l.score DESC
+    LIMIT :limit
+    """
+)
+
+_WEAKNESS_SQL = text(
+    """
+    SELECT d.id AS doc_id, d.title AS title,
+           split_part(replace(d.user_tags::text, '"', ''), '/', 3) AS subject,
+           count(l.id) AS linked,
+           count(pr.study_question_id) FILTER (WHERE pr.last_outcome IS NOT NULL) AS attempted,
+           count(*) FILTER (WHERE pr.last_outcome = 'correct') AS correct
+    FROM documents d
+    JOIN study_concept_links l ON l.concept_doc_id = d.id AND l.link_source = 'embedding'
+    LEFT JOIN study_question_progress pr
+      ON pr.study_question_id = l.question_id AND pr.user_id = :uid
+    WHERE d.user_tags::text LIKE :like AND d.deleted_at IS NULL
+    GROUP BY d.id, d.title, subject
+    """
+)
+
+
+async def related_questions(
+    session: AsyncSession, user_id: int, doc_id: int, limit: int = 20
+) -> dict:
+    """개념 doc 의 관련 기출 + 내 정답률(전체 링크 기준 집계 + 상위 N 표시용)."""
+    agg = (
+        await session.execute(_AGG_SQL, {"uid": user_id, "doc_id": doc_id})
+    ).mappings().first()
+    rows = (
+        await session.execute(
+            _QROWS_SQL, {"uid": user_id, "doc_id": doc_id, "limit": limit}
+        )
+    ).mappings().all()
+
+    linked = (agg["linked"] if agg else 0) or 0
+    attempted = (agg["attempted"] if agg else 0) or 0
+    correct = (agg["correct"] if agg else 0) or 0
+    accuracy = round(100 * correct / attempted) if attempted else None
+
+    return {
+        "linked": linked,
+        "attempted": attempted,
+        "correct": correct,
+        "accuracy": accuracy,
+        "questions": [
+            {
+                "id": r["id"],
+                "subject": r["subject"],
+                "exam_round": r["exam_round"],
+                "qnum": r["qnum"],
+                "score": round(r["score"], 3) if r["score"] is not None else None,
+                "last_outcome": r["last_outcome"],
+                "review_stage": r["review_stage"],
+            }
+            for r in rows
+        ],
+    }
+
+
+async def weakness_map(
+    session: AsyncSession, user_id: int, topic_name: str, limit: int = 12
+) -> dict:
+    """개념 약점 지도 — 링크된 기출 정답률로 개념 채색. 약점(attempted>0·정답률<60%) 우선 정렬."""
+    like = f"%@library/{topic_name}/%"
+    rows = (
+        await session.execute(_WEAKNESS_SQL, {"uid": user_id, "like": like})
+    ).mappings().all()
+
+    concepts = []
+    for r in rows:
+        attempted = r["attempted"] or 0
+        correct = r["correct"] or 0
+        accuracy = round(100 * correct / attempted) if attempted else None
+        if accuracy is None:
+            state = "unattempted"
+        elif accuracy < _ACCURACY_WEAK_PCT:
+            state = "weak"
+        else:
+            state = "ok"
+        concepts.append(
+            {
+                "doc_id": r["doc_id"],
+                "title": r["title"],
+                "subject": r["subject"],
+                "linked": r["linked"] or 0,
+                "attempted": attempted,
+                "accuracy": accuracy,
+                "state": state,
+            }
+        )
+
+    # 약점 우선(정답률 오름차순) → 미평가는 뒤로. 홈 위젯용 상위 N.
+    weak = sorted(
+        [c for c in concepts if c["state"] == "weak"],
+        key=lambda c: (c["accuracy"], -c["attempted"], c["doc_id"]),
+    )
+    return {
+        "weak": weak[:limit],
+        "weak_total": len(weak),
+        "evaluated_total": sum(1 for c in concepts if c["state"] != "unattempted"),
+    }

frontend/src/routes/study/+page.svelte

@@ -4,7 +4,7 @@
   import { onMount } from 'svelte';
   import { api } from '$lib/api';
   import { addToast } from '$lib/stores/toast';
-  import { BookOpen, PenLine, GraduationCap, FolderKanban, Layers, Repeat, Flag, Inbox, Activity, CalendarCheck } from 'lucide-svelte';
+  import { BookOpen, PenLine, GraduationCap, FolderKanban, Layers, Repeat, Flag, Inbox, Activity, CalendarCheck, Target } from 'lucide-svelte';
 
   let cardReviewCount = $state(0);
   let questionFlagCount = $state(0);
@@ -12,6 +12,7 @@
   // 오늘의 공부 (이론 홈)
   let curriculum = $state(null);
   let todayConcepts = $state([]);
+  let weakConcepts = $state([]);        // 약점 개념(관련 기출 정답률 낮음)
   let dashLoading = $state(true);
 
   let readPct = $derived(
@@ -28,10 +29,15 @@
       curriculum = cur;
       todayConcepts = today?.concepts ?? [];
     } catch {
-      // 대시보드 실패해도 허브 나머지는 동작 (조용히)
+      // 코어 대시보드 실패해도 허브 나머지는 동작 (조용히)
     } finally {
       dashLoading = false;
     }
+    // 약점 개념 = 비차단(신규 엔드포인트 실패해도 코어 대시보드 블랙아웃 방지)
+    try {
+      const weak = await api('/study/concepts/weakness-map?limit=5');
+      weakConcepts = weak?.weak ?? [];
+    } catch {}
   }
 
   async function markRead(doc) {
@@ -121,6 +127,22 @@
           {/each}
         </ul>
       {/if}
+
+      {#if weakConcepts.length > 0}
+        <div class="mt-4 pt-3 border-t border-default">
+          <div class="text-xs text-dim mb-2 flex items-center gap-1.5">
+            <Target size={13} class="text-error" /> 약점 개념 <span class="text-faint">(관련 기출 정답률 낮음)</span>
+          </div>
+          <div class="flex flex-wrap gap-2">
+            {#each weakConcepts as w (w.doc_id)}
+              <a href="/study/read/{w.doc_id}"
+                class="text-xs rounded-full border border-error/40 bg-error/10 text-error px-3 py-1 hover:bg-error/20 transition-colors">
+                {w.title.replace(/^\d+_/, '')} <span class="font-semibold">{w.accuracy}%</span>
+              </a>
+            {/each}
+          </div>
+        </div>
+      {/if}
     {/if}
   </section>
 

frontend/src/routes/study/read/[docId]/+page.svelte

@@ -13,11 +13,12 @@
   import Button from '$lib/components/ui/Button.svelte';
   import EmptyState from '$lib/components/ui/EmptyState.svelte';
   import Skeleton from '$lib/components/ui/Skeleton.svelte';
-  import { BookOpen, ArrowLeft, Eye, EyeOff, Check, ChevronLeft, ChevronRight } from 'lucide-svelte';
+  import { BookOpen, ArrowLeft, Eye, EyeOff, Check, ChevronLeft, ChevronRight, FileQuestion } from 'lucide-svelte';
 
   let docId = $derived($page.params.docId);
 
   let concept = $state(null);
+  let relatedQ = $state(null);          // 관련 기출(이론↔문제, 비차단)
   let loading = $state(true);
   let notFound = $state(false);
   let mode = $state('read');            // 'read' | 'recall'(떠올리기)
@@ -25,12 +26,17 @@
   let marking = $state(false);
 
   const STAGE_LABEL = { 0: '복습 시작', 1: '복습 1단계', 2: '복습 2단계', 3: '복습 3단계', 4: '학습 완료' };
+  const OUTCOME_MARK = { correct: '○', wrong: '✕', unsure: '?' };
+  const OUTCOME_CLASS = { correct: 'text-success', wrong: 'text-error', unsure: 'text-warning' };
+  const outcomeMark = (o) => OUTCOME_MARK[o] ?? '–';
+  const outcomeClass = (o) => OUTCOME_CLASS[o] ?? 'text-faint';
 
   async function load() {
     const reqId = docId; // in-flight 가드: 백링크 연타 시 stale 응답 무시
     loading = true;
     notFound = false;
     concept = null;
+    relatedQ = null;
     revealed = {};
     mode = 'read';
     try {
@@ -41,9 +47,15 @@
       if (reqId !== docId) return;
       if (e?.status === 404) notFound = true;
       else addToast('error', '개념을 불러오지 못했습니다');
+      return; // 본문 실패 → 관련기출 스킵
     } finally {
       if (reqId === docId) loading = false;
     }
+    // 관련 기출(비차단 — 실패해도 본문 표시엔 영향 없음)
+    try {
+      const rq = await api(`/study/concepts/${reqId}/questions?limit=6`);
+      if (reqId === docId) relatedQ = rq;
+    } catch {}
   }
 
   // $effect 가 마운트 1회 + docId 변경(백링크/이전·다음) 재로드를 모두 커버 (onMount 불필요)
@@ -202,6 +214,29 @@
       </section>
     {/if}
 
+    <!-- 관련 기출 (이론↔문제 브리지) -->
+    {#if relatedQ && relatedQ.linked > 0}
+      <section class="mb-5 rounded-lg border border-default bg-surface p-4">
+        <h2 class="text-sm font-semibold text-text mb-2 flex items-center gap-1.5">
+          <FileQuestion size={15} class="text-accent" /> 관련 기출
+          <span class="ml-1 text-xs font-normal text-dim">
+            {relatedQ.linked}문항{#if relatedQ.accuracy !== null} · 정답률 <span class="{relatedQ.accuracy < 60 ? 'text-error' : 'text-text'} font-medium">{relatedQ.accuracy}%</span>{:else} · 아직 안 풂{/if}
+          </span>
+        </h2>
+        <ul class="space-y-0.5">
+          {#each relatedQ.questions as q (q.id)}
+            <li>
+              <a href="/study/topics/4/questions/{q.id}"
+                class="flex items-center gap-2 text-xs py-1 text-dim hover:text-accent transition-colors">
+                <span class="{outcomeClass(q.last_outcome)} shrink-0 w-4 text-center font-bold">{outcomeMark(q.last_outcome)}</span>
+                <span class="truncate">{q.subject ?? '기출'}{#if q.exam_round} · {q.exam_round}{/if}</span>
+              </a>
+            </li>
+          {/each}
+        </ul>
+      </section>
+    {/if}
+
     <!-- 액션바 -->
     <div class="flex items-center gap-2 border-t border-default pt-4 mt-2">
       {#if concept.prev_id}

migrations/382_study_concept_links.sql

@@ -0,0 +1,15 @@
+-- 382_study_concept_links.sql — 개념문서 ↔ 기출문항 링크 (이론↔문제 브리지, Stage B).
+-- concept_doc_id=documents.id, question_id=study_questions.id — FK 없음(hot 테이블 락 회피, 선례).
+-- link_source: 'embedding'(bge-m3 코사인 top-k, 주력) | 'ref'(해설 .md 참조, 후속 enrichment).
+-- score=코사인 유사도(0~1). UNIQUE(doc,question,source) — source별 공존 허용(재튜닝=source 전삭제 후 재삽입).
+CREATE TABLE IF NOT EXISTS study_concept_links (
+  id             bigserial PRIMARY KEY,
+  concept_doc_id bigint NOT NULL,
+  question_id    bigint NOT NULL,
+  link_source    text   NOT NULL,
+  score          double precision,
+  created_at     timestamptz NOT NULL DEFAULT now(),
+  CONSTRAINT uq_concept_link UNIQUE (concept_doc_id, question_id, link_source)
+);
+CREATE INDEX IF NOT EXISTS idx_concept_links_doc ON study_concept_links(concept_doc_id);
+CREATE INDEX IF NOT EXISTS idx_concept_links_q ON study_concept_links(question_id);

scripts/concept_links_backfill.sql

@@ -0,0 +1,23 @@
+-- concept_links_backfill.sql — 개념↔문항 임베딩 링크 재생성 (Stage B, 멱등·재실행 안전).
+-- 정찰 확정: bge-m3 1024d 코사인, per-concept top-k=10, threshold 0.62 → ~2362링크·284/289개념·964문항.
+-- 재튜닝 시 DELETE(embedding 소스만) 후 재삽입 = ref 링크(후속) 불변. 개념 doc = 가스기사 태그.
+DELETE FROM study_concept_links WHERE link_source = 'embedding';
+INSERT INTO study_concept_links (concept_doc_id, question_id, link_source, score)
+WITH cd AS (
+  SELECT id, embedding FROM documents
+  WHERE user_tags::text LIKE '%@library/가스기사/%'
+    AND deleted_at IS NULL AND embedding IS NOT NULL
+),
+ranked AS (
+  SELECT cd.id AS concept_doc_id, q.id AS question_id,
+         1 - (q.embedding <=> cd.embedding) AS score,
+         row_number() OVER (PARTITION BY cd.id ORDER BY q.embedding <=> cd.embedding) AS rn
+  FROM cd
+  JOIN study_questions q
+    ON q.study_topic_id = 4 AND q.embedding IS NOT NULL
+   AND q.deleted_at IS NULL AND q.is_active
+)
+SELECT concept_doc_id, question_id, 'embedding', score
+FROM ranked
+WHERE rn <= 10 AND score >= 0.62
+ON CONFLICT (concept_doc_id, question_id, link_source) DO NOTHING;