How to find out page number by given row identifier

[xtremerui]

Hi, thank you first for the work here.

This issue is more like a question as in title.

Our current implementation:

• we have a drawer section shows the pagination of our items on the left. There is a item details section on the right. User can use the pagination in the drawer to browse all items and select one to view the detail.

Our problem:

• when we have an item id in URL and navigate to it, we want the pagination lands on the page that the item is in, not other pages that user need to click next or prev to find the right one.

For example:

>Flop.Repo.insert_all(MyApp.Pet, [
>  %{name: "Harry", age: 4, species: "C. lupus"},
>  %{name: "Maggie", age: 1, species: "O. cuniculus"},
>  %{name: "Patty", age: 2, species: "C. aegagrus"}
>])

>params = %{order_by: ["name", "age"], page_size: 2}

>{:ok, {results, meta}} =
>  Flop.validate_and_run(
>    MyApp.Pet,
>    params,
>    repo: Flop.Repo
>  )

>Enum.map(results, & &1.name)
["Harry", "Maggie"]  <---- page 1 without Patty

>meta.current_page
1
>meta.current_offset
0
>meta.has_next_page?
true

if the URL is /pets/Patty, how could I make params or opts to take the name Patty (not knowing it is on page 2 beforehand) so after validate_and_run the meta is like:

>meta.current_page
2
>meta.current_offset
2
>meta.has_next_page?
false

then on page the drawer lands on page 2 with the item Patty shown there?

[woylie]

You can build the base query with Flop.validate/2 and Flop.query/3. Ensure to pass the same parameters as you would in the list view. Pass pagination: false in the options to both functions.

Assuming you use Postgres, you can then use that base query to construct a window query that selects the row_number(), and from that, you'll be able to calculate the page number given the page size. See https://stackoverflow.com/a/6254396 for an SQL example.

[xtremerui]

Thank you very much! We have solved the problem based on above.