contextual_aliases.install

<?php

use Drupal\Core\Database\Database;

/**
 * Implements hook_install().
 *
 * Alter the existing schema for `url_alias`. Add a `context` column and
 * indices that include it.
 */
function contextual_aliases_install() {
  $spec = array(
    'description' => "The context for this alias..",
    'type' => 'varchar_ascii',
    'length' => 32,
    'not null' => FALSE,
  );
  $schema = Database::getConnection()->schema();
  $schema->addField('url_alias', 'context', $spec);

  $table = \Drupal\Core\Path\AliasStorage::schemaDefinition();
  $table['fields']['context'] = $spec;

  $schema->dropIndex('url_alias', 'alias_langcode_pid');
  $schema->dropIndex('url_alias', 'source_langcode_pid');

  $schema->addIndex('url_alias', 'alias_context_langcode_pid', [
    'alias', 'context', 'langcode', 'pid',
  ], $table);

  $schema->addIndex('url_alias', 'source_context_langcode_pid', [
    'source', 'context', 'langcode', 'pid',
  ], $table);
}

/**
 * Implements hook_uninstall().
 *
 * Revert changes from `contextual_aliases_install`.
 */
function contextual_aliases_uninstall() {
  $schema = Database::getConnection()->schema();

  $schema->dropIndex('url_alias', 'alias_context_langcode_pid');
  $schema->dropIndex('url_alias', 'source_context_langcode_pid');
  $schema->dropField('url_alias', 'context');

  $table = \Drupal\Core\Path\AliasStorage::schemaDefinition();

  $schema->addIndex('url_alias', 'alias_langcode_pid', $table['indexes']['alias_langcode_pid'], $table);
  $schema->addIndex('url_alias', 'source_langcode_pid', $table['indexes']['source_langcode_pid'], $table);
}