Debug WP Queries. Include this file in functions.php and then add ?debug=sql to any WP URL

debug-wordpress-queries.php

<?php



if ( !defined('SAVEQUERIES') && isset($_GET['debug']) && $_GET['debug'] == 'sql' )
    define('SAVEQUERIES', true);
if ( !function_exists('dump') ) :
/**
 * dump()
 *
 * @param mixed $in
 * @return mixed $in
 **/

function dump($in = null) {
    echo '<pre style="margin-left: 0px; margin-right: 0px; padding: 10px; border: solid 1px black; background-color: ghostwhite; color: black; text-align: left;">';
    foreach ( func_get_args() as $var ) {
        echo "\n";
        if ( is_string($var) ) {
            echo "$var\n";
        } else {
            var_dump($var);
        }
    }
    echo '</pre>' . "\n";
    return $in;
} # dump()
endif;

/**
 * add_stop()
 *
 * @param mixed $in
 * @param string $where
 * @return mixed $in
 **/

function add_stop($in = null, $where = null) {
    global $sem_stops;
    global $wp_object_cache;
    $queries = get_num_queries();
    $milliseconds = timer_stop() * 1000;
    $out =  "$queries queries - {$milliseconds}ms";
    if ( function_exists('memory_get_usage') ) {
        $memory = number_format(memory_get_usage() / ( 1024 * 1024 ), 1);
        $out .= " - {$memory}MB";
    }
    $out .= " - $wp_object_cache->cache_hits cache hits / " . ( $wp_object_cache->cache_hits + $wp_object_cache->cache_misses );
    if ( $where ) {
        $sem_stops[$where] = $out;
    } else {
        dump($out);
    }
    return $in;
} # add_stop()


/**
 * dump_stops()
 *
 * @param mixed $in
 * @return mixed $in
 **/

function dump_stops($in = null) {
    if ( $_POST )
        return $in;
    global $sem_stops;
    global $wp_object_cache;
    $stops = '';
    foreach ( $sem_stops as $where => $stop )
        $stops .= "$where: $stop\n";
    dump("\n" . trim($stops) . "\n");
    if ( defined('SAVEQUERIES') && $_GET['debug'] == 'sql' ) {
        global $wpdb;
        foreach ( $wpdb->queries as $key => $data ) {
            $query = rtrim($data[0]);
            $duration = number_format($data[1] * 1000, 1) . 'ms';
            $loc = trim($data[2]);
            $loc = preg_replace("/(require|include)(_once)?,\s*/ix", '', $loc);
            $loc = "\n" . preg_replace("/,\s*/", ",\n", $loc) . "\n";
            dump($query, $duration, $loc);
        }
    }
    if ( $_GET['debug'] == 'cache' )
        dump($wp_object_cache->cache);
    if ( $_GET['debug'] == 'cron' ) {
        $crons = get_option('cron');
        foreach ( $crons as $time => $_crons ) {
            if ( !is_array($_crons) )
                continue;
            foreach ( $_crons as $event => $_cron ) {
                foreach ( $_cron as $details ) {
                    $date = date('Y-m-d H:m:i', $time);
                    $schedule = isset($details['schedule']) ? "({$details['schedule']})" : '';
                    if ( $details['args'] )
                        dump("$date: $event $schedule", $details['args']);
                    else
                        dump("$date: $event $schedule");
                }
            }
        }
    }
    return $in;
} # dump_stops()
add_action('init', create_function('$in', '
    return add_stop($in, "Load");
    '), 10000000);
add_action('template_redirect', create_function('$in', '
    return add_stop($in, "Query");
    '), -10000000);
add_action('wp_footer', create_function('$in', '
    return add_stop($in, "Display");
    '), 10000000);
add_action('admin_footer', create_function('$in', '
    return add_stop($in, "Display");
    '), 10000000);

/**
 * init_dump()
 *
 * @return void
 **/

function init_dump() {
    global $hook_suffix;
    if ( !is_admin() || empty($hook_suffix) ) {
        add_action('wp_footer', 'dump_stops', 10000000);
        add_action('admin_footer', 'dump_stops', 10000000);
    } else {
        add_action('wp_footer', 'dump_stops', 10000000);
        add_action("admin_footer-$hook_suffix", 'dump_stops', 10000000);
    }
} # init_dump()
add_action('wp_print_scripts', 'init_dump');


/**
 * dump_phpinfo()
 *
 * @return void
 **/

function dump_phpinfo() {
    if ( isset($_GET['debug']) && $_GET['debug'] == 'phpinfo' ) {
        phpinfo();
        die;
    }
} # dump_phpinfo()
add_action('init', 'dump_phpinfo');


/**
 * dump_http()
 *
 * @param array $args
 * @param string $url
 * @return array $args
 **/

function dump_http($args, $url) {
    dump(preg_replace("|/[0-9a-f]{32}/?$|", '', $url));
    return $args;
} # dump_http()


/**
 * dump_trace()
 *
 * @return void
 **/

function dump_trace() {
    $backtrace = debug_backtrace();
    foreach ( $backtrace as $trace )
        dump(
            'File/Line: ' . $trace['file'] . ', ' . $trace['line'],
            'Function / Class: ' . $trace['function'] . ', ' . $trace['class']
            );
} # dump_trace()
if ( $_GET['debug'] == 'http' )
    add_filter('http_request_args', 'dump_http', 0, 2);
    
?>