Google Firestore array_contains 查询失效问题求助

Firestore的array-contains查询对象时，要求完全匹配对象的所有键值对。你现在查询的是{ ID: posilekId }，但DietDays集合里Meals数组的元素肯定还包含Portions等其他字段，两者结构不一致，所以查不到匹配的文档。

方案1：优化数据结构（推荐） #

在DietDays文档里新增一个MealIDs数组，专门存储关联的Posilek ID字符串。这样查询时直接用array-contains匹配字符串，既高效又准确。

修改后的代码示例：

exports.updateDietDaysWhenMealChanges = functions.firestore.document("Posilek/{posilekId}").onUpdate((change, context) => {
  const posilekId = context.params.posilekId;
  const posilekAfter = change.after.data();
  
  // 改为查询MealIDs数组包含posilekId的文档
  return db.collection("DietDays").where("MealIDs", "array-contains", posilekId).get()
    .then(snapshot => {
      if (snapshot.empty) {
        functions.logger.log("No matching DietDay found");
        return null;
      } else {
        return Promise.all(snapshot.docs.map(dietDayDoc => {
          const meals = dietDayDoc.data().Meals;
          const mealIndex = meals.findIndex(meal => meal.ID === posilekId);
          meals[mealIndex] = { ID: posilekId, Portions: posilekAfter.Portions };
          functions.logger.log(`Editing meal in DietDay with ID: ${dietDayDoc.id}`);
          return dietDayDoc.ref.update({ Meals: meals });
        }));
      }
    });
});

同时，记得在创建或更新DietDays文档时，同步维护MealIDs数组——添加Meal时把对应ID推入数组，删除Meal时移除对应ID。

方案2：内存过滤（不推荐大数据量场景） #

如果暂时不想修改数据结构，可以先获取DietDays的所有文档，再在代码里过滤出符合条件的文档：

exports.updateDietDaysWhenMealChanges = functions.firestore.document("Posilek/{posilekId}").onUpdate((change, context) => {
  const posilekId = context.params.posilekId;
  const posilekAfter = change.after.data();
  
  return db.collection("DietDays").get()
    .then(snapshot => {
      const matchingDocs = snapshot.docs.filter(doc => {
        const meals = doc.data().Meals;
        return meals.some(meal => meal.ID === posilekId);
      });
      
      if (matchingDocs.length === 0) {
        functions.logger.log("No matching DietDay found");
        return null;
      } else {
        return Promise.all(matchingDocs.map(dietDayDoc => {
          const meals = dietDayDoc.data().Meals;
          const mealIndex = meals.findIndex(meal => meal.ID === posilekId);
          meals[mealIndex] = { ID: posilekId, Portions: posilekAfter.Portions };
          functions.logger.log(`Editing meal in DietDay with ID: ${dietDayDoc.id}`);
          return dietDayDoc.ref.update({ Meals: meals });
        }));
      }
    });
});

注意：这种方法会读取DietDays集合的所有文档，数据量大时会消耗更多资源、性能下降，仅适合小数据集临时使用。

内容的提问来源于stack exchange，提问作者flicknba