Drupal 8 - Resizing field with existing data - Change text field max length

mymodule.install.php

<?php

//
// ATTENTION!
// This method of resizing field data TRUNCATES the information present in the field.
// This is heavily based on the solution available at https://github.com/evolvingweb/custom_field_resize
// with only a minor tweak to truncate field data before resizing the field, so we don't get an SQL error.
//


/**
 * Shrink the length of "field_short_title" to 45 characters.
 */
function module_name_update_8001() {
  // Prepare relevant variables.
  $entity_type  = 'paragraph';
  $field_name   = 'field_short_title';
  $field_length = 45;

  // Update database schema.
  $database = \Drupal::database();
  // Resize the main field data table.
  $database->query("UPDATE {$entity_type}__{$field_name} SET field_short_title_value = LEFT(RTRIM(field_short_title_value), {$field_length});");
  $database->query("ALTER TABLE {$entity_type}__{$field_name} MODIFY {$field_name}_value VARCHAR({$field_length})");
  // Resize the revision field data table (if revisions are enabled).
  $database->query("UPDATE {$entity_type}_revision__{$field_name} SET field_short_title_value = LEFT(RTRIM(field_short_title_value), {$field_length});");
  $database->query("ALTER TABLE {$entity_type}_revision__{$field_name} MODIFY {$field_name}_value VARCHAR({$field_length})");

  // Update storage schema.
  $storage_key = $entity_type . '.field_schema_data.' . $field_name;
  $storage_schema = \Drupal::keyValue('entity.storage_schema.sql');
  $field_schema = $storage_schema->get($storage_key);
  $field_schema[$entity_type . '__' . $field_name]['fields'][$field_name . '_value']['length'] = $field_length;
  $field_schema[$entity_type . '_revision__' . $field_name]['fields'][$field_name . '_value']['length'] = $field_length;
  $storage_schema->set($storage_key, $field_schema);

  // Update field configuration.
  $config = \Drupal::configFactory()
    ->getEditable("field.storage.{$entity_type}.{$field_name}");
  $config->set('settings.max_length', $field_length);
  $config->save(TRUE);

  // Update field storage configuration.
  FieldStorageConfig::loadByName($entity_type, $field_name)->save();

  return t('Length of @entity-type.@field-name was updated to @field-length', [
    '@entity-type' => $entity_type,
    '@field-name' => $field_name,
    '@field-length' => $field_length,
  ]);
}