Fix for memory problem in export index (#879)

As file value was used to store all of the documents it stopped the script when the value was getting too big due to number of documents stored in it. Value was not used so I just removed it.

Author: PWalkow

Service/ExportService.php

@@ -82,7 +82,6 @@ public function exportIndex(
         $filename = str_replace('.json', '', $filename);
         $writer = $this->getWriter($this->getFilePath($filename.'.json'), $metadata);
 
-        $file = [];
         foreach ($results as $data) {
             if ($counter >= $maxLinesInFile) {
                 $writer->finalize();
@@ -99,7 +98,6 @@ public function exportIndex(
 
             $doc = array_intersect_key($data, array_flip(['_id', '_type', '_source']));
             $writer->push($doc);
-            $file[] = $doc;
             $progress->advance();
             $counter++;
         }