diff --git a/core/modules/views/src/Plugin/views/filter/StringFilter.php b/core/modules/views/src/Plugin/views/filter/StringFilter.php
index 99ca0e6..1f55c59 100644
--- a/core/modules/views/src/Plugin/views/filter/StringFilter.php
+++ b/core/modules/views/src/Plugin/views/filter/StringFilter.php
@@ -274,6 +274,12 @@ protected function valueForm(&$form, FormStateInterface $form_state) {
     }
   }
 
+  /**
+   * Overwrite equal operator for complex expressions.
+   *
+   * @return string
+   *   Overwritten, database driver specific operator.
+   */
   function operator() {
     return $this->getConditionOperator($this->operator == '=' ? 'LIKE' : 'NOT LIKE');
   }