PDO::fetchAll vs. PDO::fetch ve smyčce

Malý benchmark s 200 000 náhodnými záznamy. Podle očekávání je metoda fetchAll rychlejší, ale vyžaduje více paměti.

Result :
fetchAll : 0.35965991020203s, 100249408b
fetch : 0.39197015762329s, 440b

Použitý srovnávací kód:

<?php
// First benchmark : speed
$dbh = new PDO('mysql:dbname=testage;dbhost=localhost', 'root', '');
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sql = 'SELECT * FROM test_table WHERE 1';
$stmt = $dbh->query($sql);
$data = array();
$start_all = microtime(true);
$data = $stmt->fetchAll();
$end_all = microtime(true);

$stmt = $dbh->query($sql);
$data = array();
$start_one = microtime(true);
while($data = $stmt->fetch()){}
$end_one = microtime(true);

// Second benchmark : memory usage
$stmt = $dbh->query($sql);
$data = array();
$memory_start_all = memory_get_usage();
$data = $stmt->fetchAll();
$memory_end_all = memory_get_usage();

$stmt = $dbh->query($sql);
$data = array();
$memory_end_one = 0;
$memory_start_one = memory_get_usage();
while($data = $stmt->fetch()){
  $memory_end_one = max($memory_end_one, memory_get_usage());
}

echo 'Result : <br/>
fetchAll : ' . ($end_all - $start_all) . 's, ' . ($memory_end_all - $memory_start_all) . 'b<br/>
fetch : ' . ($end_one - $start_one) . 's, ' . ($memory_end_one - $memory_start_one) . 'b<br/>';