Optimization of database queries for multicategories

While working on one interesting module, I noticed an interesting pattern.
When I use the module, the content begins to form and output faster.
I experimented a little and decided to share this solution with you :)
The request processing speed increases almost 10 times. Tested experimentally.

A detailed description of all measurements can be found on my website

Installation
Open File engine/engine.php
Find the code:
$where_category = "category = '{$get_cats}'";
                
                }
            
            }
After it insert:
            $db->query("SELECT id FROM ".PREFIX."_post WHERE {$where_category} AND approve=1" . $where_date);
            $ids = array();
            while($r = $db->get_row()) $ids[] = $r['id'];
            if(count($ids)) $ids = implode(',',$ids);
            else $ids = 0;
            $where_category = "id IN ($ids)";That's it :)

Why should I install this hack even though the cache is turned on?
1. The cache is still periodically cleaned.
2. In DLE up to version 11, only the first 6 navigation pages are cached. Version 11 already has 11 pages. But still, all other pages are output without cache.

DLE version: any