incorrect result using fnGetNodes() after a value is searched in searchbox of jquerydataTables1.9.4

I am using jquery.dataTables.js(1.9.4).
I am using checkbox for select all and deselect all,but I wanted checked value of checkbox of all pages to be persisted so I used

$(xytable.fnGetNodes()).find("input[name='chklist']").length    //to get length of checkboxes
and

$(xytable.fnGetNodes()).find("input[name='chklist']:checked").length     // to find length of checked checkboxes

here xytable -->table id

but when I search a value in search box then the content changes say from 8 results their are only 2 result displayed(which is correct) but the length I get of all the checkboxes by fnGetNodes() remain 8 and not 2(which is incorrect) !!!!