feature: Multiple indices in EntityStore

[j2L4e]

edit: I just realized, this isn't the best example, because you could already have the needed index in the tags EntityState. But you get the gist.

Example: you might want to look up items by a tag that's attached to it. Say we have an EntityStore with items where each item can have one or several tags (by id, assume a normalized state).

const items = [
  {id:1, tags: [1, 2]},
  {id:2, tags: [1]}
  {id:3, tags: [2, 3]}
];

The resulting State looks like this:

{
  entities: {
    1: {id:1, tags: [1, 2]},
    2: {id:2, tags: [1]}
    3: {id:3, tags: [2, 3]}
  },
  ids: [1,2,3]
}

Filtering or finding items by tag is cumbersome and slow. It'd be nice to get the possibility of indexing items by one or more keys different from id to get a state similar to this one:

{
  entities: {
    1: {id:1, tags: [1, 2]},
    2: {id:2, tags: [1]}
    3: {id:3, tags: [2, 3]}
  },
  entitiesByTag: {
    1: [1, 2], // just the ids for brevity, actual entities should be here
    2: [1, 3], 
    3: [3]
  },
  ids: [1,2,3]
}

Implementing this reactively isn't feasible as you'd have to either diff or reindex the entire thing on every state change.

[NetanelBasal]

Actually you can do it easily with the filterBy option:

selectAll({ filterBy: entity => entity.tags.includes(tagId) })

As for the performance, I don't think there should be a significant problem. Browsers are highly optimized when it comes to for loops. Did you experience a performance issue?

[j2L4e]

Thanks. You are right, this might be a case of premature optimization. It does have its place though, when you handle larger amounts of normalized data, especially on less powerful clients.

[NetanelBasal]

Agree, but I think it's hard to develop something that will satisfy all cases.

[hiepxanh]

I think that your case is very good example for the document @j2L4e then should we close this issue?

[NetanelBasal]

Yes. Closing for now.

[oleersoy]

There's Relational Pouch so if the store is persisted to pouchdb it might be a good solution performance wise. Hoping to get time to play with it soon.