Firebase database strucutre

Question

I\'m currently creating an e-commerce app for iOS and I\'m having trouble deciding on how to structure my database for the scenario of a user searching for an item by \"keywords

Answer 1

In Firebase, you can query using a single value or a value range, so constructing a single query to obtain items matching several keywords is not going to be possible. However, you could arrange your database so that you could easily query or a single keyword. You'd then need to combine several queries, etc.

You could arrange your data like this:

{
  "items": {
    "item1_id": {
      "brand_id": ...,
      "itemName": ...,
      "price": ...,
      "keywords": {
        "black": true,
        "t-shirt": true
      }
    }
  }
}

However, as explained in this answer, you would need to define an index for each keyword. To allow for efficient keyword-based queries, you could create your own mapping of keywords to items:

{
  "items": {
    "item1_id": {
      "brand_id": ...,
      "itemName": ...,
      "price": ...,
      "keywords": {
        "black": true,
        "t-shirt": true
      }
    }
  },
  "keywords": {
    "black": {
      "item1_id": true
    },
    "t-shirt": {
      "item1_id": true
    }
  }
}

The query for a keyword would be something like this:

let keyword = "black";
database.ref(`keywords/${keyword}`).once("value", (snapshot) => {
  snapshot.forEach((idSnapshot) => {
    database.ref(`items/${idSnapshot.key}`).once("value", (itemSnapshot) => {
      console.log(JSON.stringify(itemSnapshot.val()));
    });
  });
});

Having to maintain your own mapping of keywords to items is a little painful, but the queries will be fast. Also, Firebase's multi-location updates can make maintaining the keywords mapping a little easier. To create an item:

database.ref().update({
  "items/item1_id": {
    "brand_id": ...,
    "itemName": ...,
    "price": ...,
    "keywords": {
      "black": true,
      "t-shirt": true
    }
  },
  "keywords/black/item1_id": true,
  "keywords/t-shirt/item1_id": true
});

To change an item's keywords (remove black, add blue and leave t-shirt untouched):

database.ref().update({
  "items/item1_id/keywords": {
    "black": null,
    "blue": true
  },
  "keywords/black/item1_id": null,
  "keywords/blue/item1_id": true
});

And to delete an item:

database.ref().update({
  "items/item1_id": null,
  "keywords/blue/item1_id": null,
  "keywords/t-shirt/item1_id": null
});