docs: private void beforeBatch(BatchBackend backend) {
  		if ( this.purgeAtStart ) {
  			// purgeAll for affected entities
  			IndexedTypeSet targetedTypes = searchFactoryImplementor.getIndexedTypesPolymorphic( rootIndexedTypes );
  			for ( IndexedTypeIdentifier type : targetedTypes ) {
  				// needs do be in-sync work to make sure we wait for the end of it.
  				backend.doWorkInSync( new PurgeAllLuceneWork( tenantId, type ) );
  			}
  			if ( this.optimizeAfterPurge ) {
  				backend.optimize( targetedTypes );
  			}
  		}
  	}