In firestore, request.resource.data.size() is equivalent to the size of the document in its final form. My question is, how can I get the parameters that are being sent from the client?
Meaning, if I the client tries to update the property name, then I want to check if the client has updated name and the size of the parameters he sent is just one parameter. I would've used hasExact() if it existed, but the problem is that I'm not sure if there's an object the specifies the requested parameters.
With the current request.resource.data.size(), I'm not sure how can do the following operations:
Deny writing updatedAt property (which is being updated as the server timestamp on each update) without an additional property.
Deny updating a property that is already equivalent to the requested value.
It's difficult to tell from your question exactly what you want to do. It doesn't sound like the size of the update is the only thing you need to be looking at. Without a more concrete example, I am just going to guess what you need
But you should know that request.resource.data is a Map type object. Click through to the linked API documentation to find out what you can do with a Map. That map will contain all the fields of a document that's being updated by the client. If you want the value of one of those fields, you can say request.resource.data.f where f is the name of the field. This should help you express your logic.
If you want the value of an existing field of a document, before it's written, use the map resource.data, which works the same way.
Related
I have an app using React + Redux and coupled with Firebase for the backend.
Often times, I will want to add some new attributes to existing objects.
When doing so, existing objects won't get the attribute until they're modified with the new version of the app that handles those new attributes.
For example, let's say I have a /categories/ node, in there I've got objects such as this :
{
name: "Medical"
}
Now let's say I want to add an icon field with a default of "
Is it possible to update all categories at once so that field always exists with the default value?
Or do you handle this in the client code?
Right now I'm always testing the values to see if they're here or not, but it doesn't seem like a very good way to go about it. I'd like to have one place to define defaults.
It seems like having classes for each object type would be interesting but I'm not sure how to go about this in Redux.
Do you just use the reducer to turn all categories into class instances when you fetch them for example? I'm worried this would be heavy performance wise.
Any write operation to the Firebase Database requires that you know the exact path to the node that you're writing.
There is no built-in operation to bulk update nodes with a path that is only partially known.
You can either keep your client-side code robust enough to handle the missing properties, or you can indeed run a migration script to add the new property to each relevant node. But since that script will have to know the exact path of each node to write, it will likely first have to read/query the database to determine those paths. Depending on the number of items to update, it could possibly use multi-location updates after that to update multiple nodes in one call. E.g.
firebase.database().ref("categories").update({
"idOfMedicalCategory/icon": "newIconForMedical",
"idOfCommercialCategory/icon": "newIconForCommercial"
"idOfTechCategory/icon": "newIconForTech"
})
I'm trying to create a re-usable script for capturing record changes onSave with Server-side scripting. To do that, I need the model information for a given table, including what type each field is.
I have figured out how to get the model for my table and details for the fields:
var table = "Clients";
var myObject = app.models[table];
// Dump the properties of the 2nd field in the model
console.log("Field 2 properties: " + JSON.stringify(myObject["L"]["fields"]["1"]));
I see this:
{"name":"Client",
"key":"zzzkS1spSPKkRXMn",
"displayName":null,
"description":"Short name for client (must be unique)",
"type":{},
"required":false,
"uid":false,
"defaultValue":null,
"minLength":0,
"maxLength":null,
"integer":false,
"sortable":true,
"minValue":null,
"maxValue":null,
"regexp":null,
"regexpError":null,
"possibleValues":null,
"aggregationType":null
}
"type" looks like an empty property here and I can't seem to figure out how to get any reference to it to tell me what I need.
How do I get usable type information for a given field in a model?
Right now, App Maker doesn't expose an API to access the model metadata.
You snippet is actually accessing App Maker's internal state and might break in future releases (the "L" property is actually obfuscated by a JS compiler and not designed to be accessed from user land).
We know this kind of meta-programming is handy and this is something we might add in the future based on user feedback. Please feel free to submit a request feature in our issue tracker (https://developers.google.com/appmaker/support).
Let's say I've got a FooEnity with an id of 35 exposed by a web service, and it is located at at /myhost/api/fooentity/35.
Now I want to implement a PATCH call to allow partial updates to FooEntity (so let's say 2 of the 25 available fields are passed up to be updated).
My question is, should the PATCH content (json/xml) include the id of 35? The address of the entity is specified by the URI, and id is not an updateable field, and if it was included it is an extra validation to make sure both ids match. All of this suggests No. Still, it feels weird not having it in there.
What is the appropriate way to do this?
(Note, question is language independent, but is implemented in the ASP.NET 4.0 Web API framework, if that influences anyone's answer).
That's a great question!
There are two ways you can handle that. You can either raise a validation error if the id in the body is different from the id in the URI. Or you can just ignore whatever id is in the request body. If you're patching by manually copying properties, you would just not copy the id property to ignore it. If you're using a helper class to patch the entity, you could apply the patch and then set the entity's id to be whatever came in on the URI just to make sure that it keeps the same id after the patch.
Whichever option you pick is really up to you. Sending back a 400 if the request body id doesn't match the entity id might be a little clearer for clients so they understand that the id won't be changed, but it also requires you to write more code to implement.
this is one of the few moments I couldn't find the same question that I have at this place so I'm trying to describe my problem and hope to get some help an ideas!
Let's say...
I want to design a RESTful API for a domain model, that might have entities/resources like the following:
class Product
{
String id;
String name;
Price price;
Set<Tag> tags;
}
class Price
{
String id;
String currency;
float amount;
}
class Tag
{
String id;
String name;
}
The API might look like:
GET /products
GET /products/<product-id>
PUT /prices/<price-id>?currency=EUR&amount=12.34
PATCH /products/<product-id>?name=updateOnlyName
When it comes to updating references:
PATCH /products/<product-id>?price=<price-id>
PATCH /products/<product-id>?price=
may set the Products' Price-reference to another existing Price, or delete this reference.
But how can I add a new reference of an existing Tag to a Product?
If I wanted to store that reference in a relational database, I needed a relationship table 'products_tags' for that many-to-many-relationship, which brings us to a clear solution:
POST /product_tags [product: <product-id>, tag: <tag-id>]
But a document-based NoSQL database (like MongoDB) could store this as a one-to-many-relationship for each Product, so I don't need to model a 'new resource' that has to be created to save a relationship.
But
POST /products/<product-id>/tags/ [name: ...]
creates a new Tag (in a Product),
PUT /products/<product-id>/tags/<tag-id>?name=
creates a new Tag with <tag-id> or replaces an existing
Tag with the same id (in a Product),
PATCH /products/<product-id>?tags=<tag-id>
sets the Tag-list and doesn't add a new Tag, and
PATCH /products/<product-id>/tags/<tag-id>?name=...
sets a certain attribute of a Tag.
So I might want to say something link this:
ATTACH /products/<product-id>?tags=<tag-id>
ATTACH /products/<product-id>/tags?tag=<tag-id>
So the point is:
I don't want to create a new resource,
I don't want to set the attribute of a resource, but
I want to ADD a resource to another resources attribute, which is a set. ^^
Since everything is about resources, one could say:
I want to ATTACH a resource to another.
My question: Which Method is the right one and how should the URL look like?
Your REST is an application state driver, not aimed to be reflection of your entity relationships.
As such, there's no 'if this was the case in the db' in REST. That said, you have pretty good URIs.
You talk about IDs. What is a tag? Isn't a tag a simple string? Why does it have an id? Why isn't its id its namestring?
Why not have PUT /products/<product-id>/tags/tag_name=?
PUT is idempotent, so you are basically asserting the existance of a tag for the product referred to by product-id. If you send this request multiple times, you'd get 201 Created the first time and 200 OK the next time.
If you are building a simple system with a single concurrent user running on a single web server with no concurrency in requests, you may stop reading now
If someone in between goes and deletes that tag, your next put request would re-create the tag. Is this what you want?
With optimistic concurrency control, you would pass along the ETag a of the document everytime, and return 409 Conflict if you have a newer version b on the server and the diff, a..b cannot be reconciled. In the case of tags, you are just using PUT and DELETE verbs; so you wouldn't have to diff/look at reconciliation.
If you are building a moderately advanced concurrent system, with first-writer-wins semantics, running on a single sever, you can stop reading now
That said, I don't think you have considered your transactional boundaries. What are you modifying? A resource? No, you are modifying value objects of the product resource; its tags. So then, according to your model of resources, you should be using PATCH. Do you care about concurrency? Well, then you have much more to think about with regards to PATCH:
How do you represent the diff of a hierarchial JSON object?
How do you know what PATCH requests that conflict in a semantic way - i.e. we may not care about DELETEs on Tags, but two other properties might interact semantically.
The RFC for HTTP PATCH says this:
With PATCH, however, the enclosed entity contains a set of
instructions describing how a resource currently residing on the
origin server should be modified to produce a new version. The PATCH
method affects the resource identified by the Request-URI, and it also
MAY have side effects on other resources; i.e., new resources may be
created, or existing ones modified, by the application of a PATCH.
PATCH is neither safe nor idempotent as defined by [RFC2616], Section
9.1.
I'm probably going to stop putting strange ideas in your head now. Comment if you want me to continue down this path a bit longer ;). Suffice to say that there are many more considerations that can be done.
I want to maintain db cache(some keywords) in the servlet. When I am typing for 'a' I have 1000 keywords in Db which starts with 'a' and presently I am using js file to store all the keywords in cache. I want to maintain the DB cache in servlet also and decrease the browser cache and next hitting keyword matches in the servlet Db, I want to retrieve the top 10 keywords for the this hitting.
Can you tell me how can I create the servlet cache? Can you provide any pseudo code for that?
Thanks,
Murali
I can imagine you have a Servlet that accesses the Database in order to retrieve the top 10 keyboards based on the input delivered. That means whenever an A is pressed in the input field, you must use an XMLHttpRequest to call the servlet with that input.
The servlet should return you a list of keywords which you should parse and translate properly to your user again. (you could do this in multiple ways. An easy way is to just let the servlet respond with HTML for you,which you can set with Javascript in an element (innerHTML)).
As for caching, the servlet could use some cache and identify the requested input. You can build an own cache by generating a key from the input and the result of that input should be put into a Map.
You could also use an existing caching framework, like EHCache.