Reuse unchanged community summaries

src/graph/community.ts

@@ -24,8 +24,15 @@
  *   - kg_stats 展示社区分布
  */
 
+import { createHash } from "node:crypto";
 import { DatabaseSync, type DatabaseSyncInstance } from "@photostructure/sqlite";
-import { updateCommunities } from "../store/store.ts";
+import {
+  getCommunitySummary,
+  getCommunitySummaryBySignature,
+  pruneCommunitySummaries,
+  updateCommunities,
+  upsertCommunitySummary,
+} from "../store/store.ts";
 
 export interface CommunityResult {
   labels: Map<string, string>;
@@ -168,14 +175,17 @@ export function getCommunityPeers(db: DatabaseSyncInstance, nodeId: string, limi
 
 import type { CompleteFn } from "../engine/llm.ts";
 import type { EmbedFn } from "../engine/embed.ts";
-import { upsertCommunitySummary, pruneCommunitySummaries } from "../store/store.ts";
 
 const COMMUNITY_SUMMARY_SYS = `你是知识图谱摘要引擎。根据节点列表，用简短的描述概括这组节点的主题领域。
 要求：
 - 只返回短语本身，不要解释
 - 描述涵盖的工具/技术/任务领域
 - 不要使用"社区"这个词`;
 
+function buildCommunityMemberSignature(memberIds: string[]): string {
+  return createHash("sha1").update([...memberIds].sort().join(",")).digest("hex");
+}
+
 /**
  * 为所有社区生成 LLM 摘要描述 + embedding 向量
  *
@@ -192,6 +202,25 @@ export async function summarizeCommunities(
 
   for (const [communityId, memberIds] of communities) {
     if (memberIds.length === 0) continue;
+    const memberSignature = buildCommunityMemberSignature(memberIds);
+
+    const current = getCommunitySummary(db, communityId);
+    if (current?.memberSignature === memberSignature && current.summary.trim()) {
+      continue;
+    }
+
+    const reusable = getCommunitySummaryBySignature(db, memberSignature);
+    if (reusable?.summary.trim()) {
+      upsertCommunitySummary(
+        db,
+        communityId,
+        reusable.summary,
+        memberIds.length,
+        reusable.embedding,
+        memberSignature,
+      );
+      continue;
+    }
 
     const placeholders = memberIds.map(() => "?").join(",");
     const members = db.prepare(`
@@ -238,12 +267,12 @@ export async function summarizeCommunities(
         }
       }
 
-      upsertCommunitySummary(db, communityId, cleaned, memberIds.length, embedding);
+      upsertCommunitySummary(db, communityId, cleaned, memberIds.length, embedding, memberSignature);
       generated++;
     } catch (err) {
       console.log(`  [WARN] community summary failed for ${communityId}: ${err}`);
     }
   }
 
   return generated;
-}
+}

src/store/db.ts

@@ -5,6 +5,7 @@
  * Email: Wywelljob@gmail.com
  */
 
+import { createHash } from "node:crypto";
 import { DatabaseSync, type DatabaseSyncInstance } from "@photostructure/sqlite";
 import { mkdirSync } from "fs";
 import { homedir } from "os";
@@ -51,7 +52,16 @@ export function closeDb(): void {
 function migrate(db: DatabaseSyncInstance): void {
   db.exec(`CREATE TABLE IF NOT EXISTS _migrations (v INTEGER PRIMARY KEY, at INTEGER NOT NULL)`);
   const cur = (db.prepare("SELECT MAX(v) as v FROM _migrations").get() as any)?.v ?? 0;
-  const steps = [m1_core, m2_messages, m3_signals, m4_fts5, m5_vectors, m6_communities];
+  const steps = [
+    m1_core,
+    m2_messages,
+    m3_signals,
+    m4_fts5,
+    m5_vectors,
+    m6_communities,
+    m7_community_signature,
+    m8_backfill_community_signatures,
+  ];
   for (let i = cur; i < steps.length; i++) {
     steps[i](db);
     db.prepare("INSERT INTO _migrations (v,at) VALUES (?,?)").run(i + 1, Date.now());
@@ -180,12 +190,49 @@ function m5_vectors(db: DatabaseSyncInstance): void {
 function m6_communities(db: DatabaseSyncInstance): void {
   db.exec(`
     CREATE TABLE IF NOT EXISTS gm_communities (
-      id          TEXT PRIMARY KEY,
-      summary     TEXT NOT NULL,
-      node_count  INTEGER NOT NULL DEFAULT 0,
-      embedding   BLOB,
-      created_at  INTEGER NOT NULL,
-      updated_at  INTEGER NOT NULL
+      id               TEXT PRIMARY KEY,
+      summary          TEXT NOT NULL,
+      node_count       INTEGER NOT NULL DEFAULT 0,
+      embedding        BLOB,
+      member_signature TEXT,
+      created_at       INTEGER NOT NULL,
+      updated_at       INTEGER NOT NULL
     );
   `);
 }
+
+function m7_community_signature(db: DatabaseSyncInstance): void {
+  const cols = db.prepare("PRAGMA table_info(gm_communities)").all() as Array<{ name?: string }>;
+  const hasMemberSignature = cols.some((col) => col.name === "member_signature");
+  if (!hasMemberSignature) {
+    db.exec("ALTER TABLE gm_communities ADD COLUMN member_signature TEXT");
+  }
+  db.exec("CREATE INDEX IF NOT EXISTS ix_gm_communities_member_signature ON gm_communities(member_signature)");
+}
+
+function m8_backfill_community_signatures(db: DatabaseSyncInstance): void {
+  const missing = db.prepare(`
+    SELECT id FROM gm_communities
+    WHERE member_signature IS NULL OR member_signature=''
+  `).all() as Array<{ id: string }>;
+
+  for (const row of missing) {
+    const members = db.prepare(`
+      SELECT id FROM gm_nodes
+      WHERE community_id=? AND status='active'
+      ORDER BY id
+    `).all(row.id) as Array<{ id: string }>;
+
+    if (!members.length) continue;
+
+    const memberSignature = createHash("sha1")
+      .update(members.map((member) => member.id).join(","))
+      .digest("hex");
+
+    db.prepare(`
+      UPDATE gm_communities
+      SET member_signature=?, updated_at=updated_at
+      WHERE id=?
+    `).run(memberSignature, row.id);
+  }
+}

src/store/store.ts

@@ -531,39 +531,85 @@ export interface CommunitySummary {
   id: string;
   summary: string;
   nodeCount: number;
+  memberSignature: string | null;
   createdAt: number;
   updatedAt: number;
 }
 
 export function upsertCommunitySummary(
-  db: DatabaseSyncInstance, id: string, summary: string, nodeCount: number, embedding?: number[],
+  db: DatabaseSyncInstance,
+  id: string,
+  summary: string,
+  nodeCount: number,
+  embedding?: number[] | Uint8Array,
+  memberSignature?: string,
 ): void {
   const now = Date.now();
-  const blob = embedding ? new Uint8Array(new Float32Array(embedding).buffer) : null;
+  const blob = embedding
+    ? embedding instanceof Uint8Array
+      ? embedding
+      : new Uint8Array(new Float32Array(embedding).buffer)
+    : null;
   const ex = db.prepare("SELECT id FROM gm_communities WHERE id=?").get(id) as any;
   if (ex) {
     if (blob) {
-      db.prepare("UPDATE gm_communities SET summary=?, node_count=?, embedding=?, updated_at=? WHERE id=?")
-        .run(summary, nodeCount, blob, now, id);
+      db.prepare("UPDATE gm_communities SET summary=?, node_count=?, embedding=?, member_signature=?, updated_at=? WHERE id=?")
+        .run(summary, nodeCount, blob, memberSignature ?? null, now, id);
     } else {
-      db.prepare("UPDATE gm_communities SET summary=?, node_count=?, updated_at=? WHERE id=?")
-        .run(summary, nodeCount, now, id);
+      db.prepare("UPDATE gm_communities SET summary=?, node_count=?, member_signature=?, updated_at=? WHERE id=?")
+        .run(summary, nodeCount, memberSignature ?? null, now, id);
     }
   } else {
-    db.prepare("INSERT INTO gm_communities (id, summary, node_count, embedding, created_at, updated_at) VALUES (?,?,?,?,?,?)")
-      .run(id, summary, nodeCount, blob, now, now);
+    db.prepare("INSERT INTO gm_communities (id, summary, node_count, embedding, member_signature, created_at, updated_at) VALUES (?,?,?,?,?,?,?)")
+      .run(id, summary, nodeCount, blob, memberSignature ?? null, now, now);
   }
 }
 
 export function getCommunitySummary(db: DatabaseSyncInstance, id: string): CommunitySummary | null {
   const r = db.prepare("SELECT * FROM gm_communities WHERE id=?").get(id) as any;
   if (!r) return null;
-  return { id: r.id, summary: r.summary, nodeCount: r.node_count, createdAt: r.created_at, updatedAt: r.updated_at };
+  return {
+    id: r.id,
+    summary: r.summary,
+    nodeCount: r.node_count,
+    memberSignature: r.member_signature ?? null,
+    createdAt: r.created_at,
+    updatedAt: r.updated_at,
+  };
+}
+
+export function getCommunitySummaryBySignature(
+  db: DatabaseSyncInstance,
+  memberSignature: string,
+): (CommunitySummary & { embedding?: Uint8Array }) | null {
+  const r = db.prepare(`
+    SELECT * FROM gm_communities
+    WHERE member_signature=?
+    ORDER BY updated_at DESC
+    LIMIT 1
+  `).get(memberSignature) as any;
+  if (!r) return null;
+  return {
+    id: r.id,
+    summary: r.summary,
+    nodeCount: r.node_count,
+    memberSignature: r.member_signature ?? null,
+    embedding: r.embedding ? (r.embedding as Uint8Array) : undefined,
+    createdAt: r.created_at,
+    updatedAt: r.updated_at,
+  };
 }
 
 export function getAllCommunitySummaries(db: DatabaseSyncInstance): CommunitySummary[] {
   return (db.prepare("SELECT * FROM gm_communities ORDER BY node_count DESC").all() as any[])
-    .map(r => ({ id: r.id, summary: r.summary, nodeCount: r.node_count, createdAt: r.created_at, updatedAt: r.updated_at }));
+    .map(r => ({
+      id: r.id,
+      summary: r.summary,
+      nodeCount: r.node_count,
+      memberSignature: r.member_signature ?? null,
+      createdAt: r.created_at,
+      updatedAt: r.updated_at,
+    }));
 }
 
 export type ScoredCommunity = { id: string; summary: string; score: number; nodeCount: number };
@@ -640,4 +686,4 @@ export function pruneCommunitySummaries(db: DatabaseSyncInstance): number {
     )
   `).run();
   return result.changes;
-}
+}

test/graph.test.ts

@@ -11,7 +11,7 @@ import { describe, it, expect, beforeEach } from "vitest";
 import { DatabaseSync, type DatabaseSyncInstance } from "@photostructure/sqlite";
 import { createTestDb, insertNode, insertEdge } from "./helpers.ts";
 import { personalizedPageRank, computeGlobalPageRank, invalidateGraphCache } from "../src/graph/pagerank.ts";
-import { detectCommunities, getCommunityPeers } from "../src/graph/community.ts";
+import { detectCommunities, getCommunityPeers, summarizeCommunities } from "../src/graph/community.ts";
 import { detectDuplicates, dedup } from "../src/graph/dedup.ts";
 import { runMaintenance } from "../src/graph/maintenance.ts";
 import { saveVector } from "../src/store/store.ts";
@@ -194,6 +194,26 @@ describe("Community Detection", () => {
     const { count } = detectCommunities(db);
     expect(count).toBe(0);
   });
+
+  it("reuses existing summaries when a community is unchanged", async () => {
+    const a = insertNode(db, { name: "docker-build" });
+    const b = insertNode(db, { name: "docker-push" });
+    insertEdge(db, { fromId: a, toId: b });
+
+    const { communities } = detectCommunities(db);
+    let llmCalls = 0;
+    const llm = async () => {
+      llmCalls += 1;
+      return "docker deployment skills";
+    };
+
+    const first = await summarizeCommunities(db, communities, llm);
+    const second = await summarizeCommunities(db, communities, llm);
+
+    expect(first).toBe(1);
+    expect(second).toBe(0);
+    expect(llmCalls).toBe(1);
+  });
 });
 
 // ═══════════════════════════════════════════════════════════════
@@ -298,4 +318,4 @@ describe("runMaintenance", () => {
     expect(result.pagerank.topK).toHaveLength(0);
     expect(result.community.count).toBe(0);
   });
-});
+});

test/helpers.ts

@@ -113,6 +113,19 @@ export function createTestDb(): DatabaseSyncInstance {
     );
   `);
 
+  // m6: 社区摘要
+  db.exec(`
+    CREATE TABLE IF NOT EXISTS gm_communities (
+      id               TEXT PRIMARY KEY,
+      summary          TEXT NOT NULL,
+      node_count       INTEGER NOT NULL DEFAULT 0,
+      embedding        BLOB,
+      member_signature TEXT,
+      created_at       INTEGER NOT NULL,
+      updated_at       INTEGER NOT NULL
+    );
+  `);
+
   return db;
 }
 
@@ -176,4 +189,4 @@ export function insertEdge(
     "test-session",
     Date.now(),
   );
-}
+}