database_test.module

<?php

/**
 * @file
 * Database test module.
 */

use Drupal\Core\Database\Query\AlterableInterface;

/**
 * Implements hook_query_alter().
 */
function database_test_query_alter(AlterableInterface $query) {

  if ($query->hasTag('database_test_alter_add_range')) {
    $query->range(0, 2);
  }

  if ($query->hasTag('database_test_alter_add_join')) {
    $people_alias = $query->join('test', 'people', "test_task.pid = %alias.id");
    $query->addField($people_alias, 'name', 'name');
    $query->condition($people_alias . '.id', 2);
  }

  if ($query->hasTag('database_test_alter_change_conditional')) {
    $conditions =& $query->conditions();
    $conditions[0]['value'] = 2;
  }

  if ($query->hasTag('database_test_alter_change_fields')) {
    $fields =& $query->getFields();
    unset($fields['age']);
  }

  if ($query->hasTag('database_test_alter_change_expressions')) {
    $expressions =& $query->getExpressions();
    $expressions['double_age']['expression'] = 'age*3';
  }
}


/**
 * Implements hook_query_TAG_alter().
 *
 * Called by DatabaseTestCase::testAlterRemoveRange.
 */
function database_test_query_database_test_alter_remove_range_alter(AlterableInterface $query) {
  $query->range();
}