class CommentStorageSchema

class CommentStorageSchema extends SqlContentEntityStorageSchema {
    
    /**
     * {@inheritdoc}
     */
    protected function getEntitySchema(ContentEntityTypeInterface $entity_type, $reset = FALSE) {
        $schema = parent::getEntitySchema($entity_type, $reset);
        if ($data_table = $this->storage
            ->getDataTable()) {
            $schema[$data_table]['indexes'] += [
                'comment__status_pid' => [
                    'pid',
                    'status',
                ],
                'comment__num_new' => [
                    'entity_id',
                    'entity_type',
                    'comment_type',
                    'status',
                    'created',
                    'cid',
                    'thread',
                ],
                'comment__entity_langcode' => [
                    'entity_id',
                    'entity_type',
                    'comment_type',
                    'default_langcode',
                ],
            ];
        }
        return $schema;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getSharedTableFieldSchema(FieldStorageDefinitionInterface $storage_definition, $table_name, array $column_mapping) {
        $schema = parent::getSharedTableFieldSchema($storage_definition, $table_name, $column_mapping);
        $field_name = $storage_definition->getName();
        if ($table_name == 'comment_field_data') {
            // Remove unneeded indexes.
            unset($schema['indexes']['comment_field__pid__target_id']);
            unset($schema['indexes']['comment_field__entity_id__target_id']);
            switch ($field_name) {
                case 'thread':
                    // Improves the performance of the comment__num_new index defined
                    // in getEntitySchema().
                    $schema['fields'][$field_name]['not null'] = TRUE;
                    break;
                case 'entity_type':
                case 'field_name':
                    assert($storage_definition instanceof RequiredFieldStorageDefinitionInterface);
                    if ($storage_definition->isStorageRequired()) {
                        // The 'entity_type' and 'field_name' are required so they also need
                        // to be marked as NOT NULL.
                        $schema['fields'][$field_name]['not null'] = TRUE;
                    }
                    break;
                case 'created':
                    $this->addSharedTableFieldIndex($storage_definition, $schema, TRUE);
                    break;
                case 'uid':
                    $this->addSharedTableFieldForeignKey($storage_definition, $schema, 'users', 'uid');
            }
        }
        return $schema;
    }

}