Drush script shortens files with names that would be too long with s3 bucket added to uri.

s3rten.drush

#!/usr/bin/env drush

/**
 * Shortens files with names that would be too long with s3 bucket added to uri.
 *
 * Problem:
 * - In order to migrate existing files to s3 we must replace existing public://
 *   and private:// schemes to to s3://BUCKET_NAME/ in the uri column of the
 *   {file_managed} and {file_managed_revisions} tables.
 * - However, some files that previously fit in these uri columns would now be
 *   too long with the BUCKET_NAME added.
 * - Depending on the replace method used, those rows would either fail or skip
 *   (example MySQL IGNORE REPLACE).
 * - In either case, the s3 scheme would not be added, so fields configured to
 *   use s3 for upload would render these existing files as broken images.
 *
 * Solution:
 * - Shorten actual file names to fit the longest BUCKET_NAME in their full URI.
 * - Update value in uri column of {file_managed} and {file_managed_revisions}
 *   tables to match the newly renamed file.
 *
 * Drush options (required):
 * - max_len: Number of characters the uri column in {file_managed} table may
 *   have before the filename is shortened.
 * - op: May be one of:
 *   - count: Returns a the number of records that will be effected.
 *   - list: Lists the URI for records that will be effected.
 *   - move: Performs file shortening operation, moving from old to new name.
 *
 * @see system_schema()
 * @see file_entity_revisions_schema()
 */

$max_len = drush_get_option('max_len');
$op = drush_get_option('op');
if (empty($max_len) || !is_numeric($max_len)) {
  drush_set_error('NO_MAX_LENGTH', dt('The "max" option is required. Must be numeric.'));
  $missing = TRUE;
}
if (empty($op) || !in_array($op, array('count', 'list', 'move'))) {
  drush_set_error('NO_OP', dt('The "op" option is required. Must be one of "count", "list", or "move".'));
  $missing = TRUE;
}
if ($missing) {
  return;
}

// Note do not use :max or :public placeholders, as they are reserved.
$query = "SELECT fid, uri
  FROM {file_managed}
  WHERE LENGTH (uri) > :max_len
  AND (uri LIKE :scheme1 OR uri LIKE :scheme2)";
$args = array(
  ':max_len' => $max_len,
  ':scheme1' => 'public://%',
  ':scheme2' => 'private://%',
);
$records = db_query($query, $args);

if ('count' == $op) {
  $count = $records->rowCount();
  drush_print($count);
}
else {
  foreach ($records as $record) {
    if ('list' == $op) {
      drush_print($record->uri);
    }
    elseif ('move' == $op) {
      // Shorten each actual file name, and update the file and DB accordingly.
      $file = file_load($record->fid);
      // Use md5 to get a unique shortened file name.
      $pathinfo = pathinfo($record->uri);
      $destination = $pathinfo['dirname'] . '/' . md5($pathinfo['filename']) . '.' . $pathinfo['extension'];
      file_move($file, $destination, FILE_EXISTS_ERROR);
      drush_print("Moving from $record->uri to {$destination}.");
    }
  }
}