Building relational meteor databases for hierarchical structures

Question

Building relational meteor databases for hierarchical structures

Hey there, I'm diving into the world of Meteor and Mongo and I've got some basic questions on designing databases.

Imagine I'm creating a turn-based strategy game similar to Advance Wars. I'm stuck on how to structure my data efficiently.

I put together a little demo in my html:

{{#each chars}}
  <div class='char' style={{get_style}}>
      ...
  </div>
{{/each}}

For this, I have a helper set up on Template.body:

Template.body.helpers({
  chars: function() {
    return Characters.find({});
  },
  ...
})

Now, everything seems fine when running just one game. But handling multiple games concurrently is where I hit a roadblock.

One solution could involve having a Games collection wherein each Game links two or more Players, each with their own list of Characters. Each Character would then hold an x and y position. But I'm unsure about querying after replacing Characters.find({}).

Possibly something like

Game.findOne({game_id: game_id}).players[player_id].characters

could work. However, I'm not clear on the performance implications. Will Meteor fetch the entire game object every time a character moves?

Another option that requires minimal changes might be

Characters.find({game_id: 123, player_id: 1})

. This way, all Characters from all games are stored in one large collection. Though it feels odd not encapsulating Characters under a specific Game, maybe this approach is more practical.

After jotting down those thoughts, the second option seems more logical. I'd probably define other internal game objects as separate collections. Does this sound like a good plan to tackle this issue?

javascript mongodb meteor nosql

Answer 1

Answer №1

Imagine your collection contains items that have the following structure:

{
  _id: String,
  started: Date,
  players: [{
    _id: String,
    name: String,
    characters: [{
      _id: String,
      x: Number,
      y: Number
    }, {
      // ...
    }]
  }, {
    // ...
  }]
}

If you have the _id of a specific game and you want to retrieve all the players along with their characters, you can simply do the following:

let gameId = 'whatever';
const games = Games.find({
  _id: gameId
});

Once you have the games, you will be able to iterate over a single element, which is the game you selected using its unique ID.

In your template, you can then display this information as follows:

<div class="games">
  {{#each games}}
    <h1>{{started}} — The game's `started` property.</h1>
    {{#each players}}
      <div class="player" id="{{_id}}">
        <h2 id="{{_id}}">{{name}} — Player's Name</h2>
        {{#each characters}}
          <h3 id="{{_id}}">{{x}}, {{y}} — Character's Coordinates</h3>
        {{/each}}
      </div>
    {{/each}}
  {{/each}}
</div>

Take note of how _id is used based on the current context.

Alternatively, you can achieve the same result by using a plain object instead of a cursor, but only when you are certain that the query will return a single element:

let gameId = 'whatever';
const game = Games.findOne({
  _id: gameId
});

The template structure will vary in this case. Since you have a single plain object, there is no need for iteration. You can access the properties directly within a with block:

<div class="game">
  {{#with game}}
    <h1>{{started}} — Game's `started` property</h1>
    {{#each players}}
      <div class="player" id="{{_id}}">
        <h2 id="{{_id}}">{{name}} — Player's Name</h2>
        {{#each characters}}
          <h3 id="{{_id}}">{{x}}, {{y}} — Character's Coordinates</h3>
        {{/each}}
      </div>
    {{/each}}
  {{/with}}
</div>

Ensure that your template (or client side) is subscribed to the Games collection, and that this collection is published on the server providing the complete field set without querying unnecessary data.

Answer 2

Imagine your collection contains items that have the following structure:

{
  _id: String,
  started: Date,
  players: [{
    _id: String,
    name: String,
    characters: [{
      _id: String,
      x: Number,
      y: Number
    }, {
      // ...
    }]
  }, {
    // ...
  }]
}

If you have the _id of a specific game and you want to retrieve all the players along with their characters, you can simply do the following:

let gameId = 'whatever';
const games = Games.find({
  _id: gameId
});

Once you have the games, you will be able to iterate over a single element, which is the game you selected using its unique ID.

In your template, you can then display this information as follows:

<div class="games">
  {{#each games}}
    <h1>{{started}} — The game's `started` property.</h1>
    {{#each players}}
      <div class="player" id="{{_id}}">
        <h2 id="{{_id}}">{{name}} — Player's Name</h2>
        {{#each characters}}
          <h3 id="{{_id}}">{{x}}, {{y}} — Character's Coordinates</h3>
        {{/each}}
      </div>
    {{/each}}
  {{/each}}
</div>

Take note of how _id is used based on the current context.

Alternatively, you can achieve the same result by using a plain object instead of a cursor, but only when you are certain that the query will return a single element:

let gameId = 'whatever';
const game = Games.findOne({
  _id: gameId
});

The template structure will vary in this case. Since you have a single plain object, there is no need for iteration. You can access the properties directly within a with block:

<div class="game">
  {{#with game}}
    <h1>{{started}} — Game's `started` property</h1>
    {{#each players}}
      <div class="player" id="{{_id}}">
        <h2 id="{{_id}}">{{name}} — Player's Name</h2>
        {{#each characters}}
          <h3 id="{{_id}}">{{x}}, {{y}} — Character's Coordinates</h3>
        {{/each}}
      </div>
    {{/each}}
  {{/with}}
</div>

Ensure that your template (or client side) is subscribed to the Games collection, and that this collection is published on the server providing the complete field set without querying unnecessary data.

Building relational meteor databases for hierarchical structures

Answer №1

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