javascript - Why do I have not necessary pagination buttons with jQuery DataTables?

Question

I have a problem on a DataTables using pagination with server-side request.

It looks like the number of pagination buttons is not related to my results. I always have buttons for pages 1, 2, 3, 4, 5, no matter how many results I have.

My DataTables definition:

$('#tableau_reponses').DataTable({
        "ajax": {
            url: '/my_api/get_reponses_ajax',
            type: 'post',
            data: formData
        },
        "paging": true,
        "searching": false,
        "bProcessing": true,
        "serverSide": true,
        "ordering": false,
        "info": false,
        "pagingType": "numbers",
        "pageLength": 20,
        "lengthMenu": [10, 20, 50, 100],
        'order': [[1, 'asc']],
        'columnDefs': [
            {
                'targets': 0,
                'orderable': false,
                'className': 'dt-body-center',
                'render': function (data, type, full, meta){
                    return '<input type="checkbox" name="id[]" value="' + $('<div/>').text(data).html() + '">';
                }
            },
            {
                'targets': 1,
                'render': function (data) {
                    return '<td class="response_state_folder"></td>';
                }
            }
        ],
    });

On my test environment, I know I have 29 results. My pageLength is set to 20. So by default, on page 1, I have 20 results. When I select page 2, I have 9 results. So far so good. But when I select page 3, 4 or 5 (and I shouldn't be able to) I have 0 results.

Why do I have "3, 4, 5" buttons when, with 29 results, I should have only 2 pages? Of course if I have 142 results I need 8 pages...

I think I'm missing something pretty obvious here...

Thanks for your help!

===== EDIT =====

Following @Ashu's answer, I've managed to get "recordsFiltered" and "recordsTotal" in my response (respectively "20" and "29" in my example). But now, I have only one button (for page 1) where I'm expecting two.

Answer 1

Your server response must return how many rows are there in the filtered response from the database, and how many rows are there in total so as the database so it can set the pagination values right.

Example response :

{
    "draw": 1,
    "recordsTotal": 57, // these both are important and must be updated in every response 
    "recordsFiltered": 20, // 
    "data": [
        [
            "Angelica",
            "Ramos",
            "System Architect",
            "London",
            "9th Oct 09",
            "$2,875"
        ],
    ]
}

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