code: public function processDatamap_postProcessFieldArray($status, $table, $id, array &$fieldArray, DataHandler $tcemain)
      {
          if ($table !== 'tx_happyfeet_domain_model_footnote') {
              return;
          }
          if ($status === 'new') {
              $fieldArray['index_number'] = $this->getFootnoteRepository()->getLowestFreeIndexNumber();
          }
          if ($status === 'delete') {
              $fieldArray['index_number'] = 0;
          }
      }
docs: @param string $status Operation type e.g new, update, delete.
  @param string $table Database table on which the operation is performed.
  @param integer $id Table record ID.
  @param array $fieldArray Key/value pair of record fields.
  @param DataHandler $tcemain Parent class instance from which the hook method is called.
  @return void
  
  @codingStandardsIgnore PSR1.Methods.CamelCapsMethodName.NotCamelCaps