How to search for complete SKU like "K-00019" (without splitting it at "-" and without removing leading zeros)
I made a workaround: I added a computed field to the product type , copying the SKU, removing the dash/hyphen and saving this value. Instead of including the real SKU in the index, I included this stripped version.
At the form part, I added a validation function that removes dashes/hypens from the search input automatically. Just for sake of documentation:

function mymodule_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  if ($form_id == 'views_exposed_form') {
    $form['#validate'][] = 'sku_search_validate';
  }

function sku_search_validate($form, &amp;$form_state) {
  if (isset($form_state['values']['my_sku']) &amp;&amp; !empty($form_state['values']['my_sku'])) {
    $new_value = str_replace('-', '', $form_state['values']['my_sku']);
    $form['my_sku']['#parents'] = array('my_sku');
    form_set_value($form['my_sku'], $new_value, $form_state);
  }
}