Revert "Revert "perf: 空のタイムライン読み込み時の無駄なDBアクセスを削減するため、RedisタイムラインにダミーIDを挿入する機能を追加しました。""

This reverts commit b99ed65051.

packages/backend/src/core/FanoutTimelineEndpointService.ts

@@ -14,6 +14,7 @@ import type { NotesRepository } from '@/models/_.js';
 import { NoteEntityService } from '@/core/entities/NoteEntityService.js';
 import { FanoutTimelineName, FanoutTimelineService } from '@/core/FanoutTimelineService.js';
 import { UtilityService } from '@/core/UtilityService.js';
+import { IdService } from '@/core/IdService.js';
 import { isUserRelated } from '@/misc/is-user-related.js';
 import { isQuote, isRenote } from '@/misc/is-renote.js';
 import { CacheService } from '@/core/CacheService.js';
@@ -60,6 +61,7 @@ export class FanoutTimelineEndpointService {
 		private fanoutTimelineService: FanoutTimelineService,
 		private utilityService: UtilityService,
 		private channelMutingService: ChannelMutingService,
+		private idService: IdService,
 	) {
 	}
 
@@ -217,7 +219,25 @@ export class FanoutTimelineEndpointService {
 			return [...redisTimeline, ...gotFromDb];
 		}
 
-		return await ps.dbFallback(ps.untilId, ps.sinceId, ps.limit);
+		// RedisおよびDBが空の場合、次回以降の無駄なDBアクセスを防ぐためダミーIDを保存する
+		const gotFromDb = await ps.dbFallback(ps.untilId, ps.sinceId, ps.limit);
+		if (
+			redisResultIds.length === 0 &&
+			ps.sinceId == null && ps.untilId == null &&
+			gotFromDb.length === 0
+		) {
+			const dummyId = this.idService.gen();
+
+			Promise.all(ps.redisTimelines.map((tl, i) => {
+				// 有効なソースかつ結果が空だった場合のみダミーを入れる
+				if (redisResult[i] && redisResult[i].length === 0) {
+					return this.fanoutTimelineService.injectDummy(tl, dummyId);
+				}
+				return Promise.resolve();
+			}));
+		}
+
+		return gotFromDb;
 	}
 
 	private async getAndFilterFromDb(noteIds: string[], noteFilter: NoteFilter, idCompare: (a: string, b: string) => number): Promise<MiNote[]> {

packages/backend/src/core/FanoutTimelineService.ts

@@ -108,6 +108,11 @@ export class FanoutTimelineService {
 		});
 	}
 
+	@bindThis
+	public injectDummy(tl: FanoutTimelineName, id: string) {
+		return this.redisForTimelines.lpush('list:' + tl, id);
+	}
+
 	@bindThis
 	public purge(name: FanoutTimelineName) {
 		return this.redisForTimelines.del('list:' + name);

packages/backend/test/unit/FanoutTimelineEndpointService.ts

@@ -67,6 +67,7 @@ describe('FanoutTimelineEndpointService', () => {
 			.overrideProvider(FanoutTimelineService)
 			.useValue({
 				getMulti: jest.fn(),
+				injectDummy: jest.fn(),
 			})
 			.compile();
 
@@ -119,7 +120,7 @@ describe('FanoutTimelineEndpointService', () => {
 		const dbFallback = jest.fn((_untilId: string | null, _sinceId: string | null, _limit: number) => Promise.resolve([] as MiNote[]));
 
 		const ps = {
-			redisTimelines: ['homeTimeline', 'localTimeline'] as FanoutTimelineName[],
+			redisTimelines: [`homeTimeline:${alice.id}`, 'localTimeline'] as FanoutTimelineName[],
 			useDbFallback: true,
 			limit: 10,
 			allowPartial: false,
@@ -130,9 +131,6 @@ describe('FanoutTimelineEndpointService', () => {
 			sinceId: null,
 		};
 
-		// See comments in original file for logic explanation.
-		// Essentially, we expect the fallback to start from the end of the most recent reliable timeline (HTL).
-
 		await service.getMiNotes(ps);
 
 		expect(dbFallback).toHaveBeenCalled();
@@ -173,7 +171,7 @@ describe('FanoutTimelineEndpointService', () => {
 		const result = await service.getMiNotes(ps);
 
 		// With the fix, we should get note1 and note2.
-		// Without the fix, we would get only note3 (or empty if limit blocked it).
+
 		expect(result).toHaveLength(2);
 		expect(result[0].id).toBe(note1.id);
 		expect(result[1].id).toBe(note2.id);
@@ -224,7 +222,7 @@ describe('FanoutTimelineEndpointService', () => {
 		const dbFallback = jest.fn((untilId: string | null, sinceId: string | null, limit: number) => Promise.resolve([] as MiNote[]));
 
 		const ps = {
-			redisTimelines: ['homeTimeline', 'localTimeline'] as FanoutTimelineName[],
+			redisTimelines: [`homeTimeline:${alice.id}`, 'localTimeline'] as FanoutTimelineName[],
 			useDbFallback: false,
 			limit: 10,
 			allowPartial: true,
@@ -237,9 +235,72 @@ describe('FanoutTimelineEndpointService', () => {
 
 		const result = await service.getMiNotes(ps);
 
-		// With the previous logic, note3 and note4 would be filtered out because they are older than the "threshold" (end of TL1).
 		// With the fixed logic (skipping filter when !useDbFallback), all notes should be present.
 		expect(result).toHaveLength(4);
 		expect(result.map(n => n.id)).toEqual([note1.id, note2.id, note3.id, note4.id]);
 	});
+
+	// Test for dummy ID optimization
+	test('should inject dummy ID when DB fallback returns empty on initial load', async () => {
+		const redisResult: string[][] = [[], []]; // Empty timelines
+
+		fanoutTimelineService.getMulti.mockResolvedValue(redisResult);
+
+		// Mock dbFallback to return empty array
+		// eslint-disable-next-line @typescript-eslint/no-unused-vars
+		const dbFallback = jest.fn((_untilId: string | null, _sinceId: string | null, _limit: number) => Promise.resolve([] as MiNote[]));
+
+		const ps = {
+			redisTimelines: [`homeTimeline:${alice.id}`, 'localTimeline'] as FanoutTimelineName[],
+			useDbFallback: true,
+			limit: 10,
+			allowPartial: true,
+			excludePureRenotes: false,
+			dbFallback,
+			noteFilter: () => true,
+			untilId: null,
+			sinceId: null,
+		};
+
+		const result = await service.getMiNotes(ps);
+
+		expect(result).toEqual([]);
+		// Should have tried to inject dummy ID for both empty timelines
+		expect(fanoutTimelineService.injectDummy).toHaveBeenCalledTimes(2);
+		expect(fanoutTimelineService.injectDummy).toHaveBeenCalledWith(`homeTimeline:${alice.id}`, expect.any(String));
+		expect(fanoutTimelineService.injectDummy).toHaveBeenCalledWith('localTimeline', expect.any(String));
+	});
+
+	// Test for behavior when dummy ID exists
+	test('should return empty result when only dummy ID exists in Redis and DB has no newer data', async () => {
+		const now = Date.now();
+		const dummyId = idService.gen(now);
+		// Redis has only dummy ID
+		const redisResult: string[][] = [[dummyId]];
+
+		fanoutTimelineService.getMulti.mockResolvedValue(redisResult);
+
+		// Mock dbFallback (should be called to check for newer notes than the dummy ID)
+
+		// eslint-disable-next-line @typescript-eslint/no-unused-vars
+		const dbFallback = jest.fn((_untilId: string | null, _sinceId: string | null, _limit: number) => Promise.resolve([] as MiNote[]));
+
+		const ps = {
+			redisTimelines: [`homeTimeline:${alice.id}`] as FanoutTimelineName[],
+			useDbFallback: true,
+			limit: 10,
+			allowPartial: false,
+			excludePureRenotes: false,
+			dbFallback,
+			noteFilter: () => true,
+			untilId: null,
+			sinceId: null,
+		};
+
+		const result = await service.getMiNotes(ps);
+
+		expect(result).toEqual([]);
+		// Fallback should be called to check for newer notes (ascending check from dummy ID)
+		expect(dbFallback).toHaveBeenCalled();
+	});
 });