How to speed up rendering of nested simple_fields_for fields?

Question

Ruby on Rails

There are two models (product and product characteristics) connected by has_one association
There is a form - divided into two logical parts
1 For editing fields common for all products
2 Fields specific for this category
There are no questions with the first part. We use simple_form_for for the entry pulled from the database and render f.inputs. Everything is pretty slick.
But as we get to the parsial of additional fields, big brakes appear
I declare a simple_fields_for block in which we render all the same inputs for the associated characteristic record pulled from the database. So the server needs about ~ 100ms to render one checkbox. I have already thrown out everything superfluous from the extra fields parsial code. Leaving only the render of 20 checkboxes. But that was not the case WebRick claims that it takes 2 seconds to render this parshial. And the combat form hangs for 6 seconds only in this place. What could be wrong here? (I don’t even know about bringing the code - there’s nothing special to look at there).
It seems that in order to find out the state of the checkbox to display, simple_form makes a new query to the database for each input. The server log says that when the page is loaded, there are three requests to the database: we select the user, the product, the characteristics, then the parsials are rendered ...
Rails 4.2.1, simple_form_for 3.1.0

Answer 1

In general, I found a solution !! It was on github in the bug reports section of the simple_form repository.
What is the expected slowdown of using SimpleForm?
There, Mr. nashby wrote something like this in March of this year:
Accordingly, substituting wherever placeholder: false, hint: falsepossible. Got a boost from 6 seconds to 780ms.
Keep in mind in your applications;)

Answer 2

Without seeing the code, you can only wang.
6 seconds is a lot for one form. The reasons can be the following:
1. Poorly composed database queries, because of which the data loading takes too long (problem N + 1)
2. Poorly composed page / parsial structure. Parshals greatly slow down the rendering of the page, so it is worth optimizing the page structure and reducing the number of parsials