Firestore 动态子字段查询的索引优化策略

{
  "title": "Example Article",
  "year": 2023,
  "season": "Fall",
  "genres": {
    "Action": true,
    "Comedy": true,
    "Drama": true
  },
  "studios": {
    "Studio A": true,
    "Studio B": true
  },
  "id": "article-123"
}

import { collection, query, where, orderBy, limit, Query, DocumentData } from "firebase/firestore";
import { firestore } from "./firebaseConfig"; // 假设 firestore 实例已初始化

export function generateSearchQuery(
  searchTerms: string,
  filters: {
    year: number | "";
    season: string;
    genre: string;
    studio: string;
  }
): Query<DocumentData> {
  const docRef = collection(firestore, "example");
  let q = query(docRef);

  if (searchTerms) q = query(q, where("title", "==", searchTerms));
  if (filters.year) q = query(q, where("year", "==", filters.year));
  if (filters.season) q = query(q, where("season", "==", filters.season));
  // 问题所在：直接查询动态子字段
  if (filters.genre) q = query(q, where(`genres.${filters.genre}`, "==", true));
  if (filters.studio)
    q = query(q, where(`studios.${filters.studio}`, "==", true));

  q = query(q, orderBy("id", "desc"), limit(20));

  return q;
}

{
  "title": "Example Article",
  "year": 2023,
  "season": "Fall",
  "genres": {
    "Action": true,
    "Comedy": true,
    "Drama": true
  },
  "studios": {
    "Studio A": true,
    "Studio B": true
  },
  "id": "article-123",
  "keywords": [
    "Action",
    "Comedy",
    "Drama",
    "Studio A",
    "Studio B",
    "Action, Studio A",
    "Action, Studio B",
    "Comedy, Studio A",
    "Comedy, Studio B",
    "Drama, Studio A",
    "Drama, Studio B"
  ]
}

/**
 * 根据文章的流派和工作室信息生成用于查询的关键字数组。
 * 这个函数应在文档创建或更新时调用，并将生成的关键字存储在文档的 'keywords' 字段中。
 * @param genresMap 包含流派名称作为键的映射 (e.g., { "Action": true, "Comedy": true })
 * @param studiosMap 包含工作室名称作为键的映射 (e.g., { "Studio A": true, "Studio B": true })
 * @returns 包含所有流派、工作室及其组合的字符串数组。
 */
function generateDocumentKeywords(
  genresMap: { [key: string]: boolean },
  studiosMap: { [key: string]: boolean }
): string[] {
  const keywords = new Set<string>();
  const documentGenres = Object.keys(genresMap);
  const documentStudios = Object.keys(studiosMap);

  // 添加单个流派作为关键字
  documentGenres.forEach(genre => keywords.add(genre));
  // 添加单个工作室作为关键字
  documentStudios.forEach(studio => keywords.add(studio));

  // 添加流派与工作室的组合作为关键字
  for (const genre of documentGenres) {
    for (const studio of documentStudios) {
      keywords.add(`${genre}, ${studio}`);
    }
  }

  return Array.from(keywords);
}

// 示例：在保存或更新文档时如何使用
// const articleData = {
//   title: "Example Article",
//   // ... 其他字段
//   genres: { "Action": true, "Comedy": true },
//   studios: { "Studio A": true }
// };
// const articleKeywords = generateDocumentKeywords(articleData.genres, articleData.studios);
// await setDoc(docRef, { ...articleData, keywords: articleKeywords }, { merge: true });

/**
 * 根据用户选择的流派和工作室筛选条件，生成用于 array-contains 查询的目标关键字。
 * @param selectedGenre 用户选择的流派
 * @param selectedStudio 用户选择的工作室
 * @returns 组合后的关键字字符串，或空字符串如果两者都未选择。
 */
function generateSearchTarget(selectedGenre: string, selectedStudio: string): string {
  let target = "";

  if (selectedGenre) {
    target += selectedGenre;
  }

  if (selectedGenre && selectedStudio) {
    target += ", "; // 仅当两者都存在时添加分隔符
  }

  if (selectedStudio) {
    target += selectedStudio;
  }

  return target;
}

// 修改后的查询函数
export function generateSearchQuery(
  searchTerms: string,
  filters: {
    year: number | "";
    season: string;
    genre: string;
    studio: string;
  }
): Query<DocumentData> {
  const docRef = collection(firestore, "example");
  let q = query(docRef);

  if (searchTerms) q = query(q, where("title", "==", searchTerms));
  if (filters.year) q = query(q, where("year", "==", filters.year));
  if (filters.season) q = query(q, where("season", "==", filters.season));

  // 使用关键字组合进行查询
  const targetKeyword = generateSearchTarget(filters.genre, filters.studio);
  if (targetKeyword) {
    q = query(q, where("keywords", "array-contains", targetKeyword));
  } else if (filters.genre) { // 如果只选择了流派
    q = query(q, where("keywords", "array-contains", filters.genre));
  } else if (filters.studio) { // 如果只选择了工作室
    q = query(q, where("keywords", "array-contains", filters.studio));
  }
  // 注意：上述 else if 逻辑是可选的，如果 generateSearchTarget 已经能处理单个字段的情况，可以简化。
  // 实际上，generateSearchTarget 已经能够正确生成单个字段的 target。
  // 所以，简化的逻辑如下：
  // const targetKeyword = generateSearchTarget(filters.genre, filters.studio);
  // if (targetKeyword) {
  //   q = query(q, where("keywords", "array-contains", targetKeyword));
  // }


  q = query(q, orderBy("id", "desc"), limit(20));

  return q;
}