Cloud Firestore query with Variable in Where clause isn't working node

Question

I'm trying to integrate firestore into my nestjs app. When i try to retrieve data from firestore using where clause without variable(hardcoded value) i was able to retrieve data but when i use a variable i just receive empty array.

Here is the code i try to retrieve data from firestore.

  async getUserPosts(userId: number): Promise<PostsDocument[]> {
    this.logger.log(`Getting posts for user with ID: ${userId}`);
    const snapshot = await this.postsCollection
       .where('userId', '==', userId)
       .get();
    const posts: PostsDocument[] = [];
    snapshot.forEach((doc) => {
       this.logger.debug(`Found post: ${doc.id}`);
       posts.push(doc.data());
     });
     return posts;
  }

When i replace userId variable in where clause with 1 i was receiving data but this doesn't work.

[Nest] 1854 - 07/31/2022, 10:09:58 AM LOG [PostsService] Getting posts for user with ID: 1

I did verify that userId is received based on above log.

this is my controller code

  @Get()
  getUserPosts(@Query() query: { userId: number }) {
    if (query.userId) {
        return this.postsService.getUserPosts(query.userId);
    } else {
        return this.postsService.getPosts();
    }
  }

firebase console document screenshot for .collection("posts") .where("userId", "==", 1)

Answer 1

When you use the where() method in order to build a Query it is very important that the value passed as third parameter is of the same type than the field declared as first parameter.

As shown in the comments under your question, after some debugging it appeared that you were passing a string as field value for a field that is of type number. Hence the empty QuerySnapshot.