ChangeBaseFieldType

ChangeBaseFieldType.php

<?php

function vehicle_update_8001() {
    $database = \Drupal::database();
    $transaction = $database->startTransaction();

    $entity_type_manager = \Drupal::entityTypeManager();

    // The entity whose field type needs to be updated.
    $bundle_of = 'vehicle';

    $storage = $entity_type_manager->getStorage($bundle_of);
    $bundle_definition = $entity_type_manager->getDefinition($bundle_of);

    // The primary id of the table.
    $id_key = $bundle_definition->getKey('id');

    // If there is no data table defined then use the base table.
    $table_name = $storage->getDataTable() ?: $storage->getBaseTable();
    $definition_manager = \Drupal::entityDefinitionUpdateManager();

    // Store the existing values.
    $vehiclesCC = $database->select($table_name)
        ->fields($table_name, [$id_key, 'cc'])
        ->execute()
        ->fetchAllKeyed();

    // Clear out the values. Empty all the values before removing the field.
    $database->update($table_name)
        ->fields(['cc' => NULL])
        ->execute();

    // Uninstall the field from the Entity.
    $field_storage_definition = $definition_manager->getFieldStorageDefinition('vehicle', $bundle_of);
    $definition_manager->uninstallFieldStorageDefinition($field_storage_definition);

    // Create a new field definition.
    $new_status_field = BaseFieldDefinition::create('decimal')
        ->setLabel(t('CC'))
        ->setDescription(t('The capacity of the engine in cubic centimeter.'))
        ->setDefaultValue(0.0)
        ->setRevisionable(FALSE)
        ->setTranslatable(FALSE);

    // Install the new definition.
    $definition_manager->installFieldStorageDefinition('vehicle', $bundle_of, $bundle_of, $new_status_field);

    foreach ($vehiclesCC as $id => $value) {
        $database->update($table_name)
            ->fields(['cc' => $value])
            ->condition($id_key, $id)
            ->execute();
    }

    // Commit transaction.
    unset($transaction);
}