Debug EntityFieldQueries in Drupal 7

MYMODULE.module

<?php

/**
 * Implements hook_query_TAG_alter().
 *
 * Add the tag 'debug' to any EFQ and this will print the query to the messages.
 *
 * @param \QueryAlterableInterface $query
 */
function MYMODULE_query_debug_alter(QueryAlterableInterface $query) {
  if (function_exists('dpq') && !$query->hasTag('debug-semaphore')) {
    $query->addTag('debug-semaphore');
    dpq($query);
  }
}