Reactively publish aggregations.
meteor add jcbernack:reactive-aggregate
This helper can be used to reactively publish the results of an aggregation.
ReactiveAggregate(subscription, collection, pipeline[, options])
subscriptionshould always bethisin a publication.collectionis the Mongo.Collection instance to query.pipelineis the aggregation pipeline to execute.optionsprovides further options:observeSelectorcan be given to improve efficiency. This selector is used for observing the reactive collections. If you wish to have different selectors for multiple reactive collections, uselookupCollectionsoptions.observeOptionscan be given to limit fields, further improving efficiency. Ideally used to limit fields on your query.delay(default:250) the time (in milliseconds) between re-runs caused by changes in any reactive collections in the aggregation.lookupCollectionsis keyed by your$lookup.fromcollection name(s). it takesobserveSelectorandobserveOptionsparameters. see example below. If none is given any change to the collection will cause the aggregation to be reevaluated.
options applied to the default collection
const options = {
observeSelector: {
bookId: { $exists: true },
},
observeOptions: {
limit: 10,
sort: { createdAt: -1 },
}
};
options applied to all $lookup reactive collections
const options = {
lookupCollections: {
'books': {
observeSelector: {
'releaseDate': { $gte: new Date('2010-01-01') }
},
observeOptions: {
limit: 10,
sort: { createdAt: -1 },
}
}
}
};
clientCollectiondefaults tocollection._namebut can be overriden to sent the results to a different client-side collection.
By default, any collection instances passed into the aggregation pipeline as a Mongo.Collection instance will be reactive. If you wish to opt out of reactivity for a collection in your pipeline, simply pass the Collection._name as a string.
All collections reactive:
const pipeline = [{
$lookup: {
from: Books,
localField: 'bookId',
foreignField: '_id',
as: 'books',
},
...
$lookup: {
from: Authors,
localField: 'authorId',
foreignField: '_id',
as: 'authors',
},
...
}];
Only Books collection is reactive:
const pipeline = [{
$lookup: {
from: Books,
localField: 'bookId',
foreignField: '_id',
as: 'books',
},
...
$lookup: {
from: Authors._name,
localField: 'authorId',
foreignField: '_id',
as: 'authors',
},
...
}];
A publication for one of the examples in the MongoDB docs would look like this:
import { ReactiveAggregate } from 'meteor/jcbernack:reactive-aggregate';
Meteor.publish("booksByAuthor", function () {
ReactiveAggregate(this, Books, [{
$group: {
_id: "$author",
books: { $push: "$$ROOT" }
}
}]);
});
Define the parent collection you want to run an aggregation on. Let's say:
Reports = new Meteor.Collection('Reports');
.. in a location where all your other collections are defined, say lib/collections.js
Next, prepare to publish the aggregation on the Reports collection into another client-side-only collection we'll call, clientReport.
Create the clientReport in the client side (its needed only for client use). This collection will be the destination in which the aggregation will be put into upon completion.
Now you publish the aggregation on the server:
import { ReactiveAggregate } from 'meteor/jcbernack:reactive-aggregate';
Meteor.publish("reportTotals", function() {
// Remember, ReactiveAggregate doesn't return anything
ReactiveAggregate(this, Reports, [{
// assuming our Reports collection have the fields: hours, books
$group: {
'_id': this.userId,
'hours': {
// In this case, we're running summation.
$sum: '$hours'
},
'books': {
$sum: 'books'
}
}
}, {
$project: {
// an id can be added here, but when omitted,
// it is created automatically on the fly for you
hours: '$hours',
books: '$books'
} // Send the aggregation to the 'clientReport' collection available for client use
}], { clientCollection: "clientReport" });
});
We therefore need to subscribe to the above Publish.
Meteor.subscribe("reportTotals");
Then in our Template helper:
Template.statsBrief.helpers({
reportTotals: function() {
console.log("I'm working");
return clientReport.find();
},
});
Finally, your template:
{{#each reportTotals}}Total Hours: {{hours}} <br/>Total Books: {{books}}{{/each}}
Your aggregated values will therefore be available in client-side and behave reactively just as you'd expect.
Enjoy aggregating reactively!
import { ReactiveAggregate } from 'meteor/jcbernack:reactive-aggregate';
Meteor.publish("booksByAuthor", function () {
ReactiveAggregate(this, Books, [{
$group: {
_id: "$author",
books: { $push: "$$ROOT" }
}
}], {
observeSelector: {
`${Books._name}`: {
authorId: { $exists: true },
}
}, // for Books
// for Authors get default: {}
// observeOptions: {} <- default: all reactive collections get no query options
);
});
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent