GridFieldStreamExportButton.php

<?php


/**
 * Improved GridFieldExportButton that streams CSV data to the client instead of building
 * the entire CSV in memory and sending that (which doesn't work for large data sets).
 */
class GridFieldStreamExportButton extends GridFieldExportButton
{
  /**
   * Modified export code to stream a CSV instead of SilverStripe's "build and
   * send" approach, which is memory constrained
   *
   * @param GridField $gridField
   * @param SS_HTTPRequest $request
   * @return void
   */
  public function handleExport($gridField, $request = null)
  {
    $headers = [];
    $fieldMap = $this->getExportColumnsForGridField($gridField);

    // Map source names to display names
    // If a field is callable (e.g. anonymous function) then use the source name as the header
    foreach ($fieldMap['display'] as $columnSource => $columnHeader) {
      if (!is_string($columnHeader) && is_callable($columnHeader)) {
        $headers[] = $columnSource;
      } else {
        $headers[] = $columnHeader;
      }
    }

    $this->streamCsv($gridField, $headers, $fieldMap);
  }

  /**
   * Return the columns to export
   *
   * @param GridField $gridField
   *
   * @return array
   */
  protected function getExportColumnsForGridField(GridField $gridField) {
    $exportColumns = ['formatting' => [], 'display' => []];
    /** @var \GridFieldDataColumns $dataCols */
    if($this->exportColumns) {
      $exportColumns['display'] = $this->exportColumns;
    } else if($dataCols = $gridField->getConfig()->getComponentByType('GridFieldDataColumns')) {
      $exportColumns['display'] = $dataCols->getDisplayFields($gridField);
      $exportColumns['formatting'] =$dataCols->getFieldFormatting();
    } else {
      $exportColumns['display'] = singleton($gridField->getModelClass())->summaryFields();
    }

    return $exportColumns;
  }

  public function getHTMLFragments($gridField) {
    $button = new GridField_FormAction(
      $gridField,
      'export',
      'Export to CSV (s)',
      'export',
      null
    );
    $button->setAttribute('data-icon', 'download-csv');
    $button->addExtraClass('no-ajax action_export');
    $button->setForm($gridField->getForm());
    return array(
      $this->targetFragment => '<p class="grid-csv-button">' . $button->Field() . '</p>',
    );
  }

  /**
   * Generate an stream a CSV file to the browser, without creating it all in memory first
   *
   * @param GridField $gridField
   * @param array $headers
   * @param array $fieldMap
   */
  public function streamCsv(GridField $gridField, array $headers, array $fieldMap)
  {
    $exportName = $this->getExportFilename($gridField->getModelClass());

    header("Content-Type: text/csv");
    header("Content-Disposition: attachment; filename=\"{$exportName}\"");

    // DataList iterates by loading all rows into memory
    // This doesn't work with huge numbers of records, so we iterate over query results manually here
    /** @var SQLQuery $query */
    $class = $gridField->getModelClass();
    $query = $gridField->getList()
      ->limit(0)
      ->dataQuery()
      ->query();

    // Open and output headers
    $stream = fopen('php://output', 'w');
    fputcsv($stream, $headers);

    foreach ($query->execute() as $row) {
      $record = new $class($row);
      fputcsv($stream, $this->mapRecordToCsvRow($record, $fieldMap, $gridField));
    }

    fclose($stream);
    die();
  }

  /**
   * @param DataObject $item
   * @param array $fieldMap
   * @param GridField $gridField
   * @return array
   */
  protected function mapRecordToCsvRow(DataObject $item, array $fieldMap, GridField $gridField)
  {
    $row = [];

    foreach ($fieldMap['display'] as $columnSource => $columnHeader) {
      if (!is_string($columnHeader) && is_callable($columnHeader)) {
        if ($item->hasMethod($columnSource)) {
          $relObj = $item->{$columnSource}();
        } else {
          $relObj = $item->relObject($columnSource);
        }

        $value = $columnHeader($relObj);
      } else {
        $value = $gridField->getDataFieldValue($item, $columnSource);
      }

      $row[] = isset($fieldMap['formatting'][$columnSource]) ? $fieldMap['formatting'][$columnSource]($value, $item, true) : $value;
    }

    return $row;
  }

  /**
   * @return string
   */
  protected function getExportFilename($modelClass)
  {
    $now = Date("Y-m-d-H-i");
    return "export-$now.csv";
  }
}