Parent fields are not revisionable

+++ b/paragraphs.install
@@ -255,3 +255,91 @@ function paragraphs_update_8015() {
+    // Update the field storage repository.
+    \Drupal::service('entity_field.manager')->clearCachedFieldDefinitions();
+    $definition_update_manager = \Drupal::entityDefinitionUpdateManager();
+    $last_installed_schema = \Drupal::service('entity.last_installed_schema.repository');
+
+    $storage_definition = $definition_update_manager->getFieldStorageDefinition('parent_id', 'paragraph');
+    $storage_definition->setRevisionable(TRUE);
+    $last_installed_schema->setLastInstalledFieldStorageDefinition($storage_definition);
+    $storage_definition = $definition_update_manager->getFieldStorageDefinition('parent_type', 'paragraph');
+    $storage_definition->setRevisionable(TRUE);
+    $last_installed_schema->setLastInstalledFieldStorageDefinition($storage_definition);
+    $storage_definition = $definition_update_manager->getFieldStorageDefinition('parent_field_name', 'paragraph');
+    $storage_definition->setRevisionable(TRUE);
+    $last_installed_schema->setLastInstalledFieldStorageDefinition($storage_definition);
+
+    // Update the stored field schema.
+    // @todo: There has to be a better way to do this.
+    $key = 'paragraph.field_schema_data.parent_id';
+    $field_schema = \Drupal::keyValue('entity.storage_schema.sql')->get($key);
+    $field_schema['paragraphs_item_revision_field_data']['fields']['parent_id'] = $column_schema;
+    \Drupal::keyValue('entity.storage_schema.sql')->set($key, $field_schema);
+    $key = 'paragraph.field_schema_data.parent_type';
+    $field_schema = \Drupal::keyValue('entity.storage_schema.sql')->get($key);
+    $field_schema['paragraphs_item_revision_field_data']['fields']['parent_type'] = $column_schema;
+    \Drupal::keyValue('entity.storage_schema.sql')->set($key, $field_schema);
+    $key = 'paragraph.field_schema_data.parent_field_name';
+    $field_schema = \Drupal::keyValue('entity.storage_schema.sql')->get($key);
+    $field_schema['paragraphs_item_revision_field_data']['fields']['parent_field_name'] = $column_schema;
+    \Drupal::keyValue('entity.storage_schema.sql')->set($key, $field_schema);
+  }
+  else {
+    $sandbox['#finished'] = ($sandbox['current'] / $sandbox['total']);
+  }

I think we could put this stuff in a loop for the 3 fields.

We could check if https://www.drupal.org/project/drupal/issues/2984782 makes this easier, but then we have to add a dependency on 8.7 for this and wait until May or so.

Tested the patch on a site with 800k paragraphs, took about 2min, that is better than I expected.

However, drush entup still reports that those fields need to be changed, which means that something has not been properly updated yet.

What's failing is this check "$storage_definition->isRevisionable() != $original->isRevisionable()" in "\Drupal\Core\Entity\Sql\SqlContentEntityStorageSchema::requiresFieldStorageSchemaChanges", $original still says revisionable FALSE.

The code that we have should fix that, but it looks like something doesn't work.

+++ b/paragraphs.install
@@ -346,8 +346,8 @@
-
-  drupal_set_message($sandbox['current'] . ' nodes processed.');
+  $sandbox['#finished'] = ($sandbox['current'] / $sandbox['total']);
+  return t('@count nodes processed.', ['@count' => $sandbox['current']]);
 }
 

We are processing paragraphs, not nodes ;)

Can be fixed on commit, this seems to be working well, also on very large installations.