Issue #3247781 by Taran2L, drunken monkey: Fixed error on database update...

Search API 1.x, dev (xxxx-xx-xx):

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- #3247781 by Taran2L, drunken monkey: Fixed error on database update because

  of task table UNIQUE key.

- #3228382 by mikran, drunken monkey: Added an "Entity type" field.

- #3222644 by johne, drunken monkey: Made

  ContentEntityTrackingManager::filterValidItemIds() public.

  protected function getEntitySchema(ContentEntityTypeInterface $entity_type, $reset = FALSE): array {

    $schema = parent::getEntitySchema($entity_type, $reset);

    if ($data_table = $this->storage->getBaseTable()) {

      $data = 'data';

    $data_table = $this->storage->getBaseTable();

    if ($data_table) {

      $column = 'data';

      // MySQL cannot handle UNIQUE indices on TEXT/BLOB fields without a prefix

      // length.

      if ($this->database->driver() === 'mysql') {

        $data = ['data', 255];

        // From the MySQL documentation:

        // https://dev.mysql.com/doc/refman/8.0/en/innodb-limits.html

        //

        // The index key prefix length limit is 767 bytes for InnoDB tables that

        // use the REDUNDANT or COMPACT row format. For example, you might hit

        // this limit with a column prefix index of more than 191 characters on

        // a TEXT or VARCHAR column, assuming a utf8mb4 character set and the

        // maximum of 4 bytes for each character.

        //

        // To be on the safe side let's assume utf8mb4 character set.

        $column = ['data', 191];

      }

      $schema[$data_table]['unique keys'] += [

        'task__unique' => ['type', 'server_id', 'index_id', $data],

        'task__unique' => ['type', 'server_id', 'index_id', $column],

      ];

    }