server-side rendering mysql limit n rows and paginate - php

Question

I am using server-side rendering in DataTable.
I have a variable that determines limit to number of rows from database.
I am trying to fetch, say, 100 rows, and from DataTable with pagelength of 25, paginate it upto 4 pages.
Also, if the limit variable is 4 or 10, or anything less than pagelength value, then all records will be displayed in a single page.
Here's my code:
#get datatable params
$draw = $this->request->input('draw');
$start = $this->request->input('start');
$dt_limit = $this->request->input('length'); // datatable pagination limit
$limit_rows = $this->request->input('limit');
# query
$result_product_urls = DB::table('product_match_unmatches')
->select('r_product_url', 'r_image_url_main')
->selectRaw('count(distinct s_product_url, r_product_url) as frequency,
GROUP_CONCAT(CONCAT(s_image_url, "&s_product_url=", s_product_url) SEPARATOR " | ") as source_products')
->groupBy('r_product_url')
->where('request_id', '=', $reqId)
->orderBy('frequency', 'DESC')
->take($limit_rows);
$recordsTotal = $result_product_urls->get()->count();
$urls = $result_product_urls->offset($start)->limit($dt_limit)->get();
This will always fetch 25 rows from the database, since the dataTable page-length is 25.
But I need to limit the rows based on $limit_rows value, and not $dt_limit.
If I only do $urls = $result_product_urls->get();, then if $limit_rows value is 100, all 100 rows are displayed in the same page.
How can I fetch limit rows from database, and then paginate through it?
I hope I make my post clear.

Answer 1

I'll take a stab at this, but it's not entirely clear to me the exact thing you are attempting to accomplish based on the code sample.
According to Laravel docs take and limit appear to be equivalent.
https://laravel.com/docs/5.8/queries#ordering-grouping-limit-and-offset (bottom of this section)
What it looks like the code is doing:
Using $limit_rows value with ->take() method in the $result_product_urls query builder object:
# query
$result_product_urls = DB::table('product_match_unmatches')
->select('r_product_url', 'r_image_url_main')
->selectRaw('count(distinct s_product_url, r_product_url) as frequency,
GROUP_CONCAT(CONCAT(s_image_url, "&s_product_url=", s_product_url) SEPARATOR " | ") as source_products')
->groupBy('r_product_url')
->where('request_id', '=', $reqId)
->orderBy('frequency', 'DESC')
->take($limit_rows); /* <------------- limit_rows HERE */
But then also using $dt_limit value with ->limit() method when setting the $urls variable:
$recordsTotal = $result_product_urls->get()->count();
$urls = $result_product_urls->offset($start)->limit($dt_limit)->get();/*<-- dt_limit HERE */
If you don't want to use $dt_limit as a limit then don't use it...? I think maybe what you are trying to do is have a query with a limit on the result set, and then a sub limit on that? I can't figure out a reason to want to do that, so I might be missing something. I don't think you can use ->take() and ->limit() on the same query.
Shouldn't this accomplish your goal?:
# query
$result_product_urls = DB::table('product_match_unmatches')
->select('r_product_url', 'r_image_url_main')
->selectRaw('count(distinct s_product_url, r_product_url) as frequency,
GROUP_CONCAT(CONCAT(s_image_url, "&s_product_url=", s_product_url) SEPARATOR " | ") as source_products')
->groupBy('r_product_url')
->where('request_id', '=', $reqId)
->orderBy('frequency', 'DESC');
/* ->take($limit_rows); remove this */
$recordsTotal = $result_product_urls->get()->count();
$urls = $result_product_urls->offset($start)
->limit($limit_rows) /* set limit to $limit_rows */
->get();
If not, then maybe you can clarify.

Answer 2

use offset alongwith limit i.e.
$users = DB::table('users')->skip(10)->take(5)->get();
or
$users = DB::table('users')->offset(10)->limit(5)->get();