I'm working on a project which needs to select data from Firebase on multiple fields.
I have a firebase database like this:
[{
date: "2016-01-29"
done: false
task: "hello world"
},
{
date: "2016-01-29"
done: false
task: "hello world"
}]
Now I want to query all data with date is today and done is true.
I look around google for a while but there's nothing work. Is there any one can please help me to figure this out?
You can only query on a single property with Firebase queries. So either you'll have to do the rest of the filtering client-side or you'll have to combine the values into a single 'date_done' property.
[{
date: "2016-01-29",
done: false,
date_done: "2016-01-29_false",
task: "hello world1"
},
{
date: "2016-01-29",
done: false,
date_done: "2016-01-29_false",
task: "hello world"
}]
Now you can get all the queries that were done on January 29 with:
ref.orderByChild('date_done').equalTo('2016-01-29_true').on(...
For some more information from people who asked similar questions, see:
NoSQL database design for queries with multiple restrictions (Firebase)
Query based on multiple where clauses in firebase
Firebase - How do I write multiple orderByChild for extracting data?
How to do the following query in Firebase? (more than one where condition)
Filter products on multiple child properties in Firebase
Related
i am looking for a possible solution to find results from a mongodb collection where two columns of arrays don't hold the same entries.
Something like this:
Message DB structure
{
id: ObjectId,
title: String,
body: String,
recipients: [{ObjectId, ref: 'User'}],
visualized_by: [{ObjectId, ref: 'User'}]
}
when a User visualizes the message his id gets stored in the visualized_by column
Now, from an admin panel I want to visualize only the messages that were not seen by all the recipients like this:
Message.find({recipients: {$each: {$nin: "$visualized_by"}}})
OR
Message.find({$where: {recipients: {$each: {$nin: this.visualized_by}}}})
But it does not work of course.
Any help will be appreciated.
Thanks!
I am a fairly new web developer and would need your help with a project I am currently working on. I have worked in the past on a very simple realtime database example and have little to none experience in firestore or NoSql in general.
I want to create a system which allows end-users to get an email once a week that contains a list of special offers from bars the end-user has subscribed to. The offers change each day of the week. Bar owners can fill out a form in a vue.js web application every week with their weekly special offers.
Every Monday morning a cron job has to look up which end user has subscribed to which bars and then aggregate the data and send it via email.
The question is how would you structure the data so that I can easily compose the email and send it via a cloud function?
My approach would be to have three main collections: RestaurantOwner, EndUser, SpecialOfferings
Please see the graphic for an example process:
BarOwner and EndUser are pretty straight forward. However, the difficult part is how to structure the SpecialOffers in order to be queried the right way.
My idea would be to structure it based on the calendar week and link it to the uid from the barOwner:
specialOffers: {
2019_CW27: {
barUID001: {
mon: {
title: 'Banana Daiquir',
price: 4.99,
},
tue: {
title: 'After Five',
price: 2.99,
},
wed: {
title: 'Cool Colada',
price: 6.99
},
thu: {
title: 'Crantini',
price: 5.99
},
fri: {
title: 'French Martini',
price: 4.99
}
},
barUID002: {
mon: {
title: 'Gin & Tonic',
price: 8.99,
},
tue: {
title: 'Cratini',
price: 4.99,
},
wed: {
title: 'French Martini',
price: 4.99
},
thu: {
title: 'After Five',
price: 3.99
},
fri: {
title: 'Cool Colada',
price: 6.99
}
}
},
2019_CW28: {
barUID01: {~~~},
barUID02: {~~~}
}
}
The disadvantage of this approach is that it creates a deeply nested object when you imagine that there are 52 calendar weeks, f.e 100 signed up bars à 5 special offers per week and I am not sure if I am able to query it the way I need to.
Is this approach reasonable or what would you do differently?
Thank you so much for your help! I highly appreciate it.
I'm assuming the following scenarios:
1) The bar owners make modifications to their offers very often.
2) The bar owners should be the only ones allowed to modify each bar's offers.
If you have these two scenarios, I would recommend a sub-collections approach here.
When to use sub-collections:
1) When there are lot of fields in a document. Cloud Firestore has 20,000 field limit. (If the number of Bars can exceed more than 20,000 fields)
2) When updating the parent collection is a common operation. Firestore only lets you update the document at rate of 1 write/second. (If the SpecialOffers information of each bar is modified very often. If two bar owners modify their offers, only 1 write is successful and the second write operation waits until the first is completed. This can delay the updation offers particularly at the end of a week when almost all the bars update the offers.)
3) When you want to limit the access to particular fields of a document. (If you want to restrict the access to a Bar's Offers to the barOwner alone. You can restrict the access to each document in the Bars sub-collection according to its owner using Firestore Security Rules)
So I would recommend a sub-collection Bars under the main collection SpecialOffers. This way the design becomes scalable and you can add restaurants and super-markets as other similar sub-collections in the future without heavily altering your design.
Another advantage is that sub-collections are basically collections and they don't have a limit for number of documents it can hold. So even if the number of bars registered is above 20,000 which is the limit of number of fields for a fire-store document, your sub-collection wont be having a problem but your document will run out of fields to save the offers for a new bar.
Ultimately the choice depends on your use cases.
Hope this helps.
Hi I created a SimpleSchema for a Mongo collection which has a variable number of sub-documents called measurables. Unfortunately it's been a while since I've done this and I can't remember how to insert into this type of schema! Can someone help me out?
The schema is as follows:
const ExerciseTemplates = new Mongo.Collection('ExerciseTemplates');
const ExerciseTemplateSchema = new SimpleSchema({
name: {
type: String,
label: 'name',
},
description: {
type: String,
label: 'description',
},
createdAt: {
type: Date,
label: 'date',
},
measurables: {
type: Array,
minCount: 1,
},
'measurables.$': Object,
'measurables.$.name': String,
'measurables.$.unit': String,
});
ExerciseTemplates.attachSchema(ExerciseTemplateSchema);
The method is:
Meteor.methods({
addNewExerciseTemplate(name, description, measurables) {
ExerciseTemplates.insert({
name,
description,
createdAt: new Date(),
measurables,
});
},
});
The data sent by my form for measurables is an array of objects.
The SimpleSchema docs seem to be out of date. If I use the example they show with measurables: type: [Object] for an array of objects. I get an error that the the type can't be an array and I should set it to Array.
Any suggestions would be awesome!!
Many thanks in advance!
edit:
The measurable variable contains the following data:
[{name: weight, unit: kg}]
With the schema above I get no error at all, it is silent as if it was successful, but when I check the db via CLI I have no collections. Am I doing something really stupid? When I create a new meteor app, it creates a Mongo db for me I assume - I'm not forgetting to actually create a db or something dumb?
Turns out I was stupid. The schema I posted was correct and works exactly as intended. The problem was that I defined my schema and method in a file in my imports directory, outside both client and server directories. This methods file was imported into the file with the form that calls the method, and therefore available on the client, but not imported into the server.
I guess that the method was being called on the client as a stub so I saw the console.log firing, but the method was not being called on the server therefore not hitting the db.
Good lesson for me regarding the new recommended file structure. Always import server side code in server/main.js!!! :D
Thanks for your help, thought I was going to go mad!
I'm building a very small app where the user chooses a category, then a logo from said category and submits a form.
The document with the categories and logos is a JSON, and I have a bit of experience with CouchDB, but I get the feeling that such an app is a revision conflict magnet, as it'd be difficult to keep track of different users using at the same time and trying to update the document with the same revision ID.
I haven't been able to find some code or idea dealing with this issue.
Here's how my JSON looks like:
$scope.categories = [
{
name: 'DIY',
logos : [
{
url:'img/...1.png',
votes:0
},
{
url:'img/...2.png',
votes:0
}
]
},
{
name: 'Food',
logos : [
{
url:'img/...1.png',
votes:0
},
{
url:'img/...2.png',
votes:0
},
...
Any idea on how to deal with such an issue?
Here's a live test version of the app.
It would be useful to understand the design of your app. If I were designing this, I think I would generate a new CouchDb document when the form is submitted to record each vote. This would avoid updating any shared document and any risk of conflicts. Showing the results would then be a map/reduce query on the "vote" documents.
Let's say I have the following document schema in a collection called 'users':
{
name: 'John',
items: [ {}, {}, {}, ... ]
}
The 'items' array contains objects in the following format:
{
item_id: "1234",
name: "some item"
}
Each user can have multiple items embedded in the 'items' array.
Now, I want to be able to fetch an item by an item_id for a given user.
For example, I want to get the item with id "1234" that belong to the user with name "John".
Can I do this with mongoDB? I'd like to utilize its powerful array indexing, but I'm not sure if you can run queries on embedded arrays and return objects from the array instead of the document that contains it.
I know I can fetch users that have a certain item using {users.items.item_id: "1234"}. But I want to fetch the actual item from the array, not the user.
Alternatively, is there maybe a better way to organize this data so that I can easily get what I want? I'm still fairly new to mongodb.
Thanks for any help or advice you can provide.
The question is old, but the response has changed since the time. With MongoDB >= 2.2, you can do :
db.users.find( { name: "John"}, { items: { $elemMatch: { item_id: "1234" } } })
You will have :
{
name: "John",
items:
[
{
item_id: "1234",
name: "some item"
}
]
}
See Documentation of $elemMatch
There are a couple of things to note about this:
1) I find that the hardest thing for folks learning MongoDB is UN-learning the relational thinking that they're used to. Your data model looks to be the right one.
2) Normally, what you do with MongoDB is return the entire document into the client program, and then search for the portion of the document that you want on the client side using your client programming language.
In your example, you'd fetch the entire 'user' document and then iterate through the 'items[]' array on the client side.
3) If you want to return just the 'items[]' array, you can do so by using the 'Field Selection' syntax. See http://www.mongodb.org/display/DOCS/Querying#Querying-FieldSelection for details. Unfortunately, it will return the entire 'items[]' array, and not just one element of the array.
4) There is an existing Jira ticket to add this functionality: it is https://jira.mongodb.org/browse/SERVER-828 SERVER-828. It looks like it's been added to the latest 2.1 (development) branch: that means it will be available for production use when release 2.2 ships.
If this is an embedded array, then you can't retrieve its elements directly. The retrieved document will have form of a user (root document), although not all fields may be filled (depending on your query).
If you want to retrieve just that element, then you have to store it as a separate document in a separate collection. It will have one additional field, user_id (can be part of _id). Then it's trivial to do what you want.
A sample document might look like this:
{
_id: {user_id: ObjectId, item_id: "1234"},
name: "some item"
}
Note that this structure ensures uniqueness of item_id per user (I'm not sure you want this or not).