Testing post__not_in vs filtering

test.php

<?php
/**
 * Plugin Name:     Perf Test
 * Text Domain:     perf-test
 * Domain Path:     /languages
 * Version:         0.1.0
 *
 * @package         Perf_Test
 */

function use_post__not_in( array $exclude, int $per_page ) {
	$q = new WP_Query(
		array(
			'post_status'    => 'publish',
			'posts_per_page' => $per_page,
			'post__not_in'   => $exclude,
		)
	);

	return $q->posts;
}

function use_post__not_in_ids_only( array $exclude, int $per_page ) {
	$q = new WP_Query(
		array(
			'post_status'    => 'publish',
			'posts_per_page' => $per_page,
			'post__not_in'   => $exclude,
			'fields'         => 'ids',
		)
	);

	return $q->posts;
}

function use_custom_filter_ids( array $exclude, int $per_page ) {
	$count          = count( $exclude );
	$posts_per_page = $count + $per_page;

	$q = new WP_Query(
		array(
			'post_status'    => 'publish',
			'posts_per_page' => $posts_per_page,
			'fields'         => 'ids',
		)
	);

	$result = array_filter(
		$q->posts,
		function ( $post ) use ( $exclude ) {
			return ! in_array( $post->ID, $exclude );
		}
	);

	$result = array_slice( $result, 0, $per_page );

	$q = new WP_Query(
		array(
			'post_status'    => 'publish',
			'posts_per_page' => $per_page,
			'post__in'   => $result,
		)
	);

	return $q->posts;
}

function use_custom_filter( array $exclude, int $per_page ) {
	$count          = count( $exclude );
	$posts_per_page = $count + $per_page;

	$q = new WP_Query(
		array(
			'post_status'    => 'publish',
			'posts_per_page' => $posts_per_page,
		)
	);

	$result = array_filter(
		$q->posts,
		function ( $post ) use ( $exclude ) {
			return ! in_array( $post->ID, $exclude );
		}
	);

	$result = array_slice( $result, 0, $per_page );

	return $result;
}

function use_custom_filter_ids_only( array $exclude, int $per_page ) {
	$count          = count( $exclude );
	$posts_per_page = $count + $per_page;

	$q = new WP_Query(
		array(
			'post_status'    => 'publish',
			'posts_per_page' => $posts_per_page,
			'fields'         => 'ids',
		)
	);

	$result = array_filter(
		$q->posts,
		function ( $post ) use ( $exclude ) {
			return ! in_array( $post, $exclude );
		}
	);

	$result = array_slice( $result, 0, $per_page );

	return $result;
}

function perform_test( callable $function, $exclude_count = 10, $runs = 100, $per_page = 100, $cache = false ) {
	$all_posts = get_posts(
		array(
			'post_status'    => 'publish',
			'posts_per_page' => -1,
			'fields'         => 'ids',
		)
	);

	$start = microtime( true );

	for ( $i = 0; $i < $runs; $i++ ) {
		// Random post IDs to exclude if no caching.
		if ( ! $cache ) {
			shuffle( $all_posts );
		}

		$exclude = array_slice( $all_posts, 0, $exclude_count );
		
		// Execute testing function.
		$function( $exclude, $per_page );
	}
	$end = microtime( true );
	$mem = memory_get_peak_usage( true );

	$time = $end - $start;
	$per = $time / $runs;

	return array(
		'time' => $time,
		'avg' => $per,
		'mem' => $mem,
	);
}

/**
 * Performs full test from 100 to 1000 excluded posts with step of 100
 *
 * @param callable $function
 * @return void
 */
function full_test( callable $function, $runs = 10, $per_page = 100 ) {
	for ( $i = 100; $i < 2500; $i += 100 ) { 
		$results = perform_test( $function, $i, $runs, $per_page, false );
		file_put_contents(
			$function . '_test_data.tsv',
			$runs."\t".$i."\t".$results['time']."\t".$results['avg']."\t".$results['mem']."\n",
			FILE_APPEND
		);
	}
}

function run_all()
{
	$methods = array(
		'use_post__not_in_ids_only',
		'use_custom_filter_ids_only',
		'use_post__not_in',
		'use_custom_filter_ids',
		'use_custom_filter'
	);
	
	foreach ( $methods as $method ) {
		full_test( $method );
	}
}