测试 mongo 多了个 _id 会影响多少速度

test_mongo_id.php

#! /usr/bin/env php
<?php

$lLength = array(
	'0',
	'1000',
	'10000',
);
$lSwitch = array(
	'a',
	'b',
);
$lTotal = array(
	'a' => 0,
	'b' => 0,
);
foreach (range(1, 100) as $i) {
	foreach ($lLength as $iLength) {

		$s = $iLength ? base64_encode(file_get_contents('/dev/urandom', FALSE, NULL, 0, $iLength)) : '';

		shuffle($lSwitch);

		foreach ($lSwitch as $sSwitch) {

			if ($sSwitch == 'a') {

				// uid

				$sDB = 'test_'.mt_rand();
				$oDB = (new MongoClient())->selectDB($sDB);
				$oColl = $oDB->test_a;
				$oColl->ensureIndex(
					array(
						'uid' => 1,
					),
					array(
						'unique' => 1,
					)
				);

				$fTime = microtime(TRUE);
				for ($i = 0; $i < 10000; $i++) {
					$oColl->insert(
						array(
							'uid' => $i * 3,
							'text' => $s.mt_rand(),
						)
					);
				}
				$fTime = microtime(TRUE) - $fTime;
				$oDB->drop();
				$lTotal[$sSwitch] += $fTime;
				echo 'uid: ', $fTime, "\n";

			} else {

				// _id

				$sDB = 'test_'.mt_rand();
				$oDB = (new MongoClient())->selectDB($sDB);
				$oColl = $oDB->test_b;

				$fTime = microtime(TRUE);
				for ($i = 0; $i < 10000; $i++) {
					$oColl->insert(
						array(
							'_id' => $i * 3,
							'text' => $s.mt_rand(),
						)
					);
				}
				$fTime = microtime(TRUE) - $fTime;
				$oDB->drop();
				$lTotal[$sSwitch] += $fTime;
				echo '_id: ', $fTime, "\n";
			}
		}

		echo "\n", sprintf('%.02f%%', ($lTotal['a'] / $lTotal['b'] - 1) * 100), "\n\n";
	}
}