How to avoid exponential slowdown in PHP/MYSQL? - php

Question

I'm the owner of an online browser based game that has around 300 players signed up. I've written a script to detect cheaters, but the issue is that the number of queries in said script will grow exponentially.
It works like this:
Send a query that gets player's information.
Inside of the query, run another query that gets the information of every player.
So basically I am running a query that gets every player's name and information, and inside of that query I run another query to get the information from every other player besides themself. I use this to compare and delete cheaters.
The issue is, since I have 300 players, I have to run 300 queries per player. That's 90,000 queries. If I reach 1,000 players, it would be 1,000,000 queries. There has to be a better way to do this.
My code:
<?php
require '../connect.php';
$rulerinfo = $conn->query("SELECT id, rulername, nationname, alliance, email, dateregister, user_agent, lastseen, password FROM players");
while ($rulerinfo2 = $rulerinfo->fetch_assoc()) {
$id = $rulerinfo2['id'];
$rulername = $rulerinfo2['rulername'];
$nationname = $rulerinfo2['nationname'];
$alliance = $rulerinfo2['alliance'];
$email = $rulerinfo2['email'];
$dateregister = $rulerinfo2['dateregister'];
$useragent = $rulerinfo2['user_agent'];
$lastseen = $rulerinfo2['lastseen'];
$password = $rulerinfo2['password'];
$playerinfo = $conn->query("SELECT id, rulername, nationname, alliance, email, dateregister, user_agent, lastseen, password FROM players WHERE id != '$id'");
while ($playerinfo2 = $playerinfo->fetch_assoc()) {
$id2 = $playerinfo2['id'];
$rulername2 = $playerinfo2['rulername'];
$nationname2 = $playerinfo2['nationname'];
$alliance2 = $playerinfo2['alliance'];
$email2 = $playerinfo2['email'];
$dateregister2 = $playerinfo2['dateregister'];
$useragent2 = $playerinfo2['user_agent'];
$lastseen2 = $playerinfo2['lastseen'];
$password2 = $playerinfo2['password'];
$rulerdistance = levenshtein($rulername, $rulername2);
$nationdistance = levenshtein($nationname, $nationname2);
$emaildistance = levenshtein($email, $email2);
$agentdistance = levenshtein($useragent, $useragent2) / 2;
$totaldistance = $rulerdistance + $nationdistance + $emaildistance + $agentdistance;
if ($password == $password2) {
$totaldistance = $totaldistance - 20;
}
if ($totaldistance < 0) {
$totaldistance = 0;
}
}
}
?>

Answer 1

You should only do the query once, put it in an array and work with it from there. I don't see the need to make almost the same query twice. Loop in your array a second time and just check if the id is not the same as the current.
$res = $conn->query("SELECT id, rulername, nationname, alliance, email, dateregister, user_agent, lastseen, password FROM players");
$array=array();
while ($row = $res->fetch_assoc()) {
$array[] = $row;
}
for($i=0; $i<count($array);$i++) {
for($j=0; $j<count($array); $j++) {
if ($i != $j) {
// Call your functions
$rulerdistance = levenshtein($array[$i]['rulername'], $array[$j]['rulername']);
...
}
}
}