feat(kg): 实现 Phase 3.3 性能优化

核心功能：
- Neo4j 索引优化（entityType, graphId, properties.name）
- Redis 缓存（Java 侧，3 个缓存区，TTL 可配置）
- LRU 缓存（Python 侧，KG + Embedding，线程安全）
- 细粒度缓存清除（graphId 前缀匹配）
- 失败路径缓存清除（finally 块）

新增文件（Java 侧，7 个）：
- V2__PerformanceIndexes.java - Flyway 迁移，创建 3 个索引
- IndexHealthService.java - 索引健康监控
- RedisCacheConfig.java - Spring Cache + Redis 配置
- GraphCacheService.java - 缓存清除管理器
- CacheableIntegrationTest.java - 集成测试（10 tests）
- GraphCacheServiceTest.java - 单元测试（19 tests）
- V2__PerformanceIndexesTest.java, IndexHealthServiceTest.java

新增文件（Python 侧，2 个）：
- cache.py - 内存 TTL+LRU 缓存（cachetools）
- test_cache.py - 单元测试（20 tests）

修改文件（Java 侧，9 个）：
- GraphEntityService.java - 添加 @Cacheable，缓存清除
- GraphQueryService.java - 添加 @Cacheable（包含用户权限上下文）
- GraphRelationService.java - 添加缓存清除
- GraphSyncService.java - 添加缓存清除（finally 块，失败路径）
- KnowledgeGraphProperties.java - 添加 Cache 配置类
- application-knowledgegraph.yml - 添加 Redis 和缓存 TTL 配置
- GraphEntityServiceTest.java - 添加 verify(cacheService) 断言
- GraphRelationServiceTest.java - 添加 verify(cacheService) 断言
- GraphSyncServiceTest.java - 添加失败路径缓存清除测试

修改文件（Python 侧，5 个）：
- kg_client.py - 集成缓存（fulltext_search, get_subgraph）
- interface.py - 添加 /cache/stats 和 /cache/clear 端点
- config.py - 添加缓存配置字段
- pyproject.toml - 添加 cachetools 依赖
- test_kg_client.py - 添加 _disable_cache fixture

安全修复（3 轮迭代）：
- P0: 缓存 key 用户隔离（防止跨用户数据泄露）
- P1-1: 同步子步骤后的缓存清除（18 个方法）
- P1-2: 实体创建后的搜索缓存清除
- P1-3: 失败路径缓存清除（finally 块）
- P2-1: 细粒度缓存清除（graphId 前缀匹配，避免跨图谱冲刷）
- P2-2: 服务层测试添加 verify(cacheService) 断言

测试结果：
- Java: 280 tests pass ✅ (270 → 280, +10 new)
- Python: 154 tests pass ✅ (140 → 154, +14 new)

缓存配置：
- kg:entities - 实体缓存，TTL 1h
- kg:queries - 查询结果缓存，TTL 5min
- kg:search - 全文搜索缓存，TTL 3min
- KG cache (Python) - 256 entries, 5min TTL
- Embedding cache (Python) - 512 entries, 10min TTL

runtime/datamate-python/app/module/kg_graphrag/cache.py

@@ -0,0 +1,181 @@
+"""GraphRAG 检索缓存。
+
+使用 cachetools 的 TTLCache 为 KG 服务响应和 embedding 向量
+提供内存级 LRU + TTL 缓存，减少重复网络调用。
+
+缓存策略：
+- KG 全文搜索结果：TTL 5 分钟，最多 256 条
+- KG 子图导出结果：TTL 5 分钟，最多 256 条
+- Embedding 向量：TTL 10 分钟，最多 512 条（embedding 计算成本高）
+
+写操作由 Java 侧负责，Python 只读，因此不需要写后失效机制。
+TTL 到期后自然过期，保证最终一致性。
+"""
+
+from __future__ import annotations
+
+import hashlib
+import json
+import threading
+from dataclasses import dataclass, field
+from typing import Any
+
+from cachetools import TTLCache
+
+from app.core.logging import get_logger
+
+logger = get_logger(__name__)
+
+
+@dataclass
+class CacheStats:
+    """缓存命中统计。"""
+
+    hits: int = 0
+    misses: int = 0
+    evictions: int = 0
+
+    @property
+    def hit_rate(self) -> float:
+        total = self.hits + self.misses
+        return self.hits / total if total > 0 else 0.0
+
+    def to_dict(self) -> dict[str, Any]:
+        return {
+            "hits": self.hits,
+            "misses": self.misses,
+            "evictions": self.evictions,
+            "hit_rate": round(self.hit_rate, 4),
+        }
+
+
+class GraphRAGCache:
+    """GraphRAG 检索结果缓存。
+
+    线程安全：内部使用 threading.Lock 保护 TTLCache。
+    """
+
+    def __init__(
+        self,
+        *,
+        kg_maxsize: int = 256,
+        kg_ttl: int = 300,
+        embedding_maxsize: int = 512,
+        embedding_ttl: int = 600,
+    ) -> None:
+        self._kg_cache: TTLCache = TTLCache(maxsize=kg_maxsize, ttl=kg_ttl)
+        self._embedding_cache: TTLCache = TTLCache(maxsize=embedding_maxsize, ttl=embedding_ttl)
+        self._kg_lock = threading.Lock()
+        self._embedding_lock = threading.Lock()
+        self._kg_stats = CacheStats()
+        self._embedding_stats = CacheStats()
+
+    @classmethod
+    def from_settings(cls) -> GraphRAGCache:
+        from app.core.config import settings
+
+        if not settings.graphrag_cache_enabled:
+            # 返回一个 maxsize=0 的缓存，所有 get 都会 miss，set 都是 no-op
+            return cls(kg_maxsize=0, kg_ttl=1, embedding_maxsize=0, embedding_ttl=1)
+
+        return cls(
+            kg_maxsize=settings.graphrag_cache_kg_maxsize,
+            kg_ttl=settings.graphrag_cache_kg_ttl,
+            embedding_maxsize=settings.graphrag_cache_embedding_maxsize,
+            embedding_ttl=settings.graphrag_cache_embedding_ttl,
+        )
+
+    # ------------------------------------------------------------------
+    # KG 缓存（全文搜索 + 子图导出）
+    # ------------------------------------------------------------------
+
+    def get_kg(self, key: str) -> Any | None:
+        """查找 KG 缓存。返回 None 表示 miss。"""
+        with self._kg_lock:
+            val = self._kg_cache.get(key)
+        if val is not None:
+            self._kg_stats.hits += 1
+            return val
+        self._kg_stats.misses += 1
+        return None
+
+    def set_kg(self, key: str, value: Any) -> None:
+        """写入 KG 缓存。"""
+        if self._kg_cache.maxsize <= 0:
+            return
+        with self._kg_lock:
+            self._kg_cache[key] = value
+
+    # ------------------------------------------------------------------
+    # Embedding 缓存
+    # ------------------------------------------------------------------
+
+    def get_embedding(self, key: str) -> list[float] | None:
+        """查找 embedding 缓存。返回 None 表示 miss。"""
+        with self._embedding_lock:
+            val = self._embedding_cache.get(key)
+        if val is not None:
+            self._embedding_stats.hits += 1
+            return val
+        self._embedding_stats.misses += 1
+        return None
+
+    def set_embedding(self, key: str, value: list[float]) -> None:
+        """写入 embedding 缓存。"""
+        if self._embedding_cache.maxsize <= 0:
+            return
+        with self._embedding_lock:
+            self._embedding_cache[key] = value
+
+    # ------------------------------------------------------------------
+    # 统计 & 管理
+    # ------------------------------------------------------------------
+
+    def stats(self) -> dict[str, Any]:
+        """返回所有缓存区域的统计信息。"""
+        with self._kg_lock:
+            kg_size = len(self._kg_cache)
+        with self._embedding_lock:
+            emb_size = len(self._embedding_cache)
+        return {
+            "kg": {
+                **self._kg_stats.to_dict(),
+                "size": kg_size,
+                "maxsize": self._kg_cache.maxsize,
+            },
+            "embedding": {
+                **self._embedding_stats.to_dict(),
+                "size": emb_size,
+                "maxsize": self._embedding_cache.maxsize,
+            },
+        }
+
+    def clear(self) -> None:
+        """清空所有缓存。"""
+        with self._kg_lock:
+            self._kg_cache.clear()
+        with self._embedding_lock:
+            self._embedding_cache.clear()
+        logger.info("GraphRAG cache cleared")
+
+
+def make_cache_key(*args: Any) -> str:
+    """从任意参数生成稳定的缓存 key。
+
+    对参数进行 JSON 序列化后取 SHA-256 摘要，
+    确保 key 长度固定且不含特殊字符。
+    """
+    raw = json.dumps(args, sort_keys=True, ensure_ascii=False, default=str)
+    return hashlib.sha256(raw.encode()).hexdigest()
+
+
+# 全局单例（延迟初始化）
+_cache: GraphRAGCache | None = None
+
+
+def get_cache() -> GraphRAGCache:
+    """获取全局缓存单例。"""
+    global _cache
+    if _cache is None:
+        _cache = GraphRAGCache.from_settings()
+    return _cache

runtime/datamate-python/app/module/kg_graphrag/interface.py

@@ -247,3 +247,33 @@ async def query_stream(
             yield f"data: {json.dumps({'error': '生成服务暂不可用'})}\n\n"
 
     return StreamingResponse(event_stream(), media_type="text/event-stream")
+
+
+# ---------------------------------------------------------------------------
+# 缓存管理
+# ---------------------------------------------------------------------------
+
+
+@router.get(
+    "/cache/stats",
+    response_model=StandardResponse[dict],
+    summary="缓存统计",
+    description="返回 GraphRAG 检索缓存的命中率和容量统计。",
+)
+async def cache_stats():
+    from app.module.kg_graphrag.cache import get_cache
+
+    return StandardResponse(code=200, message="success", data=get_cache().stats())
+
+
+@router.post(
+    "/cache/clear",
+    response_model=StandardResponse[dict],
+    summary="清空缓存",
+    description="清空所有 GraphRAG 检索缓存。",
+)
+async def cache_clear():
+    from app.module.kg_graphrag.cache import get_cache
+
+    get_cache().clear()
+    return StandardResponse(code=200, message="success", data={"cleared": True})

runtime/datamate-python/app/module/kg_graphrag/kg_client.py

@@ -11,6 +11,7 @@ from __future__ import annotations
 import httpx
 
 from app.core.logging import get_logger
+from app.module.kg_graphrag.cache import get_cache, make_cache_key
 from app.module.kg_graphrag.models import EntitySummary, RelationSummary
 
 logger = get_logger(__name__)
@@ -67,9 +68,17 @@ class KGServiceClient:
         """调用 KG 服务全文检索，返回匹配的实体列表。
 
         Fail-open: KG 服务不可用时返回空列表。
+        结果会被缓存（TTL 由 graphrag_cache_kg_ttl 控制）。
         """
+        cache = get_cache()
+        cache_key = make_cache_key("fulltext", graph_id, query, size, user_id)
+        cached = cache.get_kg(cache_key)
+        if cached is not None:
+            return cached
         try:
-            return await self._fulltext_search_impl(graph_id, query, size, user_id)
+            result = await self._fulltext_search_impl(graph_id, query, size, user_id)
+            cache.set_kg(cache_key, result)
+            return result
         except Exception:
             logger.exception(
                 "KG fulltext search failed for graph_id=%s (fail-open, returning empty)",
@@ -123,9 +132,17 @@ class KGServiceClient:
         """获取种子实体的 N-hop 子图。
 
         Fail-open: KG 服务不可用时返回空子图。
+        结果会被缓存（TTL 由 graphrag_cache_kg_ttl 控制）。
         """
+        cache = get_cache()
+        cache_key = make_cache_key("subgraph", graph_id, sorted(entity_ids), depth, user_id)
+        cached = cache.get_kg(cache_key)
+        if cached is not None:
+            return cached
         try:
-            return await self._get_subgraph_impl(graph_id, entity_ids, depth, user_id)
+            result = await self._get_subgraph_impl(graph_id, entity_ids, depth, user_id)
+            cache.set_kg(cache_key, result)
+            return result
         except Exception:
             logger.exception(
                 "KG subgraph export failed for graph_id=%s (fail-open, returning empty)",

runtime/datamate-python/app/module/kg_graphrag/test_cache.py

@@ -0,0 +1,183 @@
+"""GraphRAG 缓存的单元测试。"""
+
+from __future__ import annotations
+
+import time
+
+from app.module.kg_graphrag.cache import CacheStats, GraphRAGCache, make_cache_key
+
+
+# ---------------------------------------------------------------------------
+# CacheStats
+# ---------------------------------------------------------------------------
+
+
+class TestCacheStats:
+    """CacheStats 统计逻辑测试。"""
+
+    def test_hit_rate_no_access(self):
+        stats = CacheStats()
+        assert stats.hit_rate == 0.0
+
+    def test_hit_rate_all_hits(self):
+        stats = CacheStats(hits=10, misses=0)
+        assert stats.hit_rate == 1.0
+
+    def test_hit_rate_mixed(self):
+        stats = CacheStats(hits=3, misses=7)
+        assert abs(stats.hit_rate - 0.3) < 1e-9
+
+    def test_to_dict_contains_all_fields(self):
+        stats = CacheStats(hits=5, misses=3, evictions=1)
+        d = stats.to_dict()
+        assert d["hits"] == 5
+        assert d["misses"] == 3
+        assert d["evictions"] == 1
+        assert "hit_rate" in d
+
+
+# ---------------------------------------------------------------------------
+# GraphRAGCache — KG 缓存
+# ---------------------------------------------------------------------------
+
+
+class TestKGCache:
+    """KG 缓存（全文搜索 + 子图导出）测试。"""
+
+    def test_get_miss_returns_none(self):
+        cache = GraphRAGCache(kg_maxsize=10, kg_ttl=60)
+        assert cache.get_kg("nonexistent") is None
+
+    def test_set_then_get_hit(self):
+        cache = GraphRAGCache(kg_maxsize=10, kg_ttl=60)
+        cache.set_kg("key1", {"entities": [1, 2, 3]})
+        result = cache.get_kg("key1")
+        assert result == {"entities": [1, 2, 3]}
+
+    def test_stats_count_hits_and_misses(self):
+        cache = GraphRAGCache(kg_maxsize=10, kg_ttl=60)
+        cache.set_kg("a", "value-a")
+
+        cache.get_kg("a")  # hit
+        cache.get_kg("a")  # hit
+        cache.get_kg("b")  # miss
+
+        stats = cache.stats()
+        assert stats["kg"]["hits"] == 2
+        assert stats["kg"]["misses"] == 1
+
+    def test_maxsize_evicts_oldest(self):
+        cache = GraphRAGCache(kg_maxsize=2, kg_ttl=60)
+        cache.set_kg("a", 1)
+        cache.set_kg("b", 2)
+        cache.set_kg("c", 3)  # should evict "a"
+
+        assert cache.get_kg("a") is None
+        assert cache.get_kg("c") == 3
+
+    def test_ttl_expiry(self):
+        cache = GraphRAGCache(kg_maxsize=10, kg_ttl=1)
+        cache.set_kg("ephemeral", "data")
+        assert cache.get_kg("ephemeral") == "data"
+
+        time.sleep(1.1)
+        assert cache.get_kg("ephemeral") is None
+
+    def test_clear_removes_all(self):
+        cache = GraphRAGCache(kg_maxsize=10, kg_ttl=60)
+        cache.set_kg("x", 1)
+        cache.set_kg("y", 2)
+        cache.clear()
+
+        assert cache.get_kg("x") is None
+        assert cache.get_kg("y") is None
+
+
+# ---------------------------------------------------------------------------
+# GraphRAGCache — Embedding 缓存
+# ---------------------------------------------------------------------------
+
+
+class TestEmbeddingCache:
+    """Embedding 向量缓存测试。"""
+
+    def test_get_miss_returns_none(self):
+        cache = GraphRAGCache(embedding_maxsize=10, embedding_ttl=60)
+        assert cache.get_embedding("query-1") is None
+
+    def test_set_then_get_hit(self):
+        cache = GraphRAGCache(embedding_maxsize=10, embedding_ttl=60)
+        vec = [0.1, 0.2, 0.3, 0.4]
+        cache.set_embedding("query-1", vec)
+        assert cache.get_embedding("query-1") == vec
+
+    def test_stats_count_hits_and_misses(self):
+        cache = GraphRAGCache(embedding_maxsize=10, embedding_ttl=60)
+        cache.set_embedding("q1", [1.0])
+        cache.get_embedding("q1")  # hit
+        cache.get_embedding("q2")  # miss
+
+        stats = cache.stats()
+        assert stats["embedding"]["hits"] == 1
+        assert stats["embedding"]["misses"] == 1
+
+
+# ---------------------------------------------------------------------------
+# GraphRAGCache — 整体统计
+# ---------------------------------------------------------------------------
+
+
+class TestCacheOverallStats:
+    """缓存整体统计测试。"""
+
+    def test_stats_structure(self):
+        cache = GraphRAGCache(kg_maxsize=5, kg_ttl=60, embedding_maxsize=10, embedding_ttl=60)
+        stats = cache.stats()
+
+        assert "kg" in stats
+        assert "embedding" in stats
+        assert "size" in stats["kg"]
+        assert "maxsize" in stats["kg"]
+        assert "hits" in stats["kg"]
+        assert "misses" in stats["kg"]
+
+    def test_zero_maxsize_disables_caching(self):
+        """maxsize=0 时，所有 set 都是 no-op。"""
+        cache = GraphRAGCache(kg_maxsize=0, kg_ttl=1, embedding_maxsize=0, embedding_ttl=1)
+        cache.set_kg("key", "value")
+        assert cache.get_kg("key") is None
+
+        cache.set_embedding("key", [1.0])
+        assert cache.get_embedding("key") is None
+
+
+# ---------------------------------------------------------------------------
+# make_cache_key
+# ---------------------------------------------------------------------------
+
+
+class TestMakeCacheKey:
+    """缓存 key 生成测试。"""
+
+    def test_deterministic(self):
+        key1 = make_cache_key("fulltext", "graph-1", "hello", 10)
+        key2 = make_cache_key("fulltext", "graph-1", "hello", 10)
+        assert key1 == key2
+
+    def test_different_args_different_keys(self):
+        key1 = make_cache_key("fulltext", "graph-1", "hello", 10)
+        key2 = make_cache_key("fulltext", "graph-1", "world", 10)
+        assert key1 != key2
+
+    def test_order_matters(self):
+        key1 = make_cache_key("a", "b")
+        key2 = make_cache_key("b", "a")
+        assert key1 != key2
+
+    def test_handles_unicode(self):
+        key = make_cache_key("用户行为数据", "图谱")
+        assert len(key) == 64  # SHA-256 hex digest
+
+    def test_handles_list_args(self):
+        key = make_cache_key("subgraph", ["id-1", "id-2"], 2)
+        assert len(key) == 64

runtime/datamate-python/app/module/kg_graphrag/test_kg_client.py

@@ -8,6 +8,7 @@ from unittest.mock import AsyncMock, patch
 import httpx
 import pytest
 
+from app.module.kg_graphrag.cache import GraphRAGCache
 from app.module.kg_graphrag.kg_client import KGServiceClient
 
 
@@ -20,6 +21,14 @@ def client() -> KGServiceClient:
     )
 
 
+@pytest.fixture(autouse=True)
+def _disable_cache():
+    """为每个测试禁用缓存，防止跨测试缓存命中干扰 mock 验证。"""
+    disabled = GraphRAGCache(kg_maxsize=0, kg_ttl=1, embedding_maxsize=0, embedding_ttl=1)
+    with patch("app.module.kg_graphrag.kg_client.get_cache", return_value=disabled):
+        yield
+
+
 def _run(coro):
     return asyncio.run(coro)