What is the main difference between PATCH and PUT request?

Question

HTTP verbs are probably one of the most cryptic things about the HTTP protocol. They exist, and there are many of them, but why do they exist?

Rails seems to want to support many verbs and add some verbs that aren't supported by web browsers natively.

Here's an exhaustive list of http verbs: http://annevankesteren.nl/2007/10/http-methods

There the HTTP patch from the official RFC: https://datatracker.ietf.org/doc/rfc5789/?include_text=1

The PATCH method requests that a set of changes described in the request entity be applied to the resource identified by the Request- URI. The set of changes is represented in a format called a "patch document" identified by a media type. If the Request-URI does not point to an existing resource, the server MAY create a new resource, depending on the patch document type (whether it can logically modify a null resource) and permissions, etc.

The difference between the PUT and PATCH requests is reflected in the way the server processes the enclosed entity to modify the resource identified by the Request-URI. In a PUT request, the enclosed entity is considered to be a modified version of the resource stored on the origin server, and the client is requesting that the stored version be replaced. 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.

As far as I know, the PATCH verb is not used as it is in rails applications... As I understand this, the RFC patch verb should be used to send patch instructions like when you do a diff between two files. Instead of sending the whole entity again, you send a patch that could be much smaller than resending the whole entity.

Imagine you want to edit a huge file. You edit 3 lines. Instead of sending the file back, you just have to send the diff. On the plus side, sending a patch request could be used to merge files asynchronously. A version control system could potentially use the PATCH verb to update code remotely.

One other possible use case is somewhat related to NoSQL databases, it is possible to store documents. Let say we use a JSON structure to send back and forth data from the server to the client. If we wanted to delete a field, we could use a syntax similar to the one in mongodb for $unset. Actually, the method used in mongodb to update documents could be probably used to handle json patches.

Taking this example:

db.products.update(
   { sku: "unknown" },
   { $unset: { quantity: "", instock: "" } }
)

We could have something like this:

PATCH /products?sku=unknown
{ "$unset": { "quantity": "", "instock": "" } }

Last, but not least, people can say whatever they want about HTTP verbs. There is only one truth, and the truth is in the RFCs.

I spent couple of hours with google and found the answer here

PUT => If user can update all or just a portion of the record, use PUT (user controls what gets updated)

PUT /users/123/email
[email protected]

PATCH => If user can only update a partial record, say just an email address (application controls what can be updated), use PATCH.

PATCH /users/123
[description of changes]

Why Patch

PUT method need more bandwidth or handle full resources instead on partial. So PATCH was introduced to reduce the bandwidth.

Explanation about PATCH

PATCH is a method that is not safe, nor idempotent, and allows full and partial updates and side-effects on other resources.

PATCH is a method which 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.

PATCH /users/123
[
  { "op": "replace", "path": "/email", "value": "[email protected]" }
]

Here more information about put and patch

put:
If I want to update my first name, then I send a put request:

{ "first": "Nazmul", "last": "hasan" } 

But here is a problem with using put request: When I want to send put request I have to send all two parameters that is first and last (whereas I only need to update first) so it is mandatory to send them all again with put request.

patch:
patch request, on the other hand, says: only specify the data which you need to update and it won't be affecting or changing other data.
So no need to send all values again. Do I only need to change first name? Well, It only suffices to specify first in patch request.

Here are the difference between POST, PUT and PATCH methods of a HTTP protocol.

POST

A HTTP.POST method always creates a new resource on the server. Its a non-idempotent request i.e. if user hits same requests 2 times it would create another new resource if there is no constraint.

http post method is like a INSERT query in SQL which always creates a new record in database.

Example: Use POST method to save new user, order etc where backend server decides the resource id for new resource.

PUT

In HTTP.PUT method the resource is first identified from the URL and if it exists then it is updated otherwise a new resource is created. When the target resource exists it overwrites that resource with a complete new body. That is HTTP.PUT method is used to CREATE or UPDATE a resource.

http put method is like a MERGE query in SQL which inserts or updates a record depending upon whether the given record exists.

PUT request is idempotent i.e. hitting the same requests twice would update the existing recording (No new record created). In PUT method the resource id is decided by the client and provided in the request url.

Example: Use PUT method to update existing user or order.

PATCH

A HTTP.PATCH method is used for partial modifications to a resource i.e. delta updates.

http patch method is like a UPDATE query in SQL which sets or updates selected columns only and not the whole row.

Example: You could use PATCH method to update order status.

PATCH /api/users/40450236/order/10234557

Request Body: {status: 'Delivered'}