diff --git a/core/modules/views/src/EntityViewsData.php b/core/modules/views/src/EntityViewsData.php
index 1439bd2..47d44e8 100644
--- a/core/modules/views/src/EntityViewsData.php
+++ b/core/modules/views/src/EntityViewsData.php
@@ -225,7 +225,11 @@ protected function mapFieldDefinition($table, $field_name, FieldDefinitionInterf
     $field_schema = $this->getFieldStorageDefinitions()[$field_name]->getSchema();
 
     $field_definition_type = $field_definition->getType();
-    // Add all properties to views table data.
+    // Add all properties to views table data. We need an entry for each
+    // column of each field, with the first one given special treatment.
+    // @todo Introduce concept of the "main" column for a field, rather than
+    //   assuming the first one is the main column. See also what the
+    //   mapSingleFieldViewsData() method does with $first.
     $multiple = (count($field_column_mapping) > 1);
     $first = TRUE;
     foreach ($field_column_mapping as $field_column_name => $schema_field_name) {
@@ -260,6 +264,8 @@ protected function mapSingleFieldViewsData($table, $field_name, $field_type, $co
     $views_field = array();
 
     // Provide a nicer, less verbose label for the first column within a field.
+    // @todo Introduce concept of the "main" column for a field, rather than
+    //   assuming the first one is the main column.
     if ($first) {
       $views_field['title'] = $field_definition->getLabel();
     }
@@ -276,9 +282,7 @@ protected function mapSingleFieldViewsData($table, $field_name, $field_type, $co
     // @todo Allow field types to customize this.
     // @see https://www.drupal.org/node/2337515
     switch ($field_type) {
-
       // Special case a few field types.
-
       case 'timestamp':
       case 'created':
       case 'changed':
@@ -367,8 +371,10 @@ protected function mapSingleFieldViewsData($table, $field_name, $field_type, $co
    *   The field definition.
    * @param array $views_field
    *   The views field data.
+   * @param string $field_column_name
+   *   The field column being processed.
    */
-  protected function processViewsDataForLanguage($table, FieldDefinitionInterface $field_definition, array &$views_field) {
+  protected function processViewsDataForLanguage($table, FieldDefinitionInterface $field_definition, array &$views_field, $field_column_name) {
     // Apply special titles for the langcode field.
     if ($field_definition->getName() == 'langcode') {
       if ($table == $this->entityType->getDataTable() || $table == $this->entityType->getRevisionDataTable()) {
@@ -389,8 +395,10 @@ protected function processViewsDataForLanguage($table, FieldDefinitionInterface
    *   The field definition.
    * @param array $views_field
    *   The views field data.
+   * @param string $field_column_name
+   *   The field column being processed.
    */
-  protected function processViewsDataForEntityReference($table, FieldDefinitionInterface $field_definition, array &$views_field) {
+  protected function processViewsDataForEntityReference($table, FieldDefinitionInterface $field_definition, array &$views_field, $field_column_name) {
 
     // @todo Should the actual field handler respect that this just renders a
     //   number?
@@ -432,7 +440,7 @@ protected function processViewsDataForEntityReference($table, FieldDefinitionInt
    * Processes the views data for a text field with formatting.
    *
    * @param string $table
-   *   The table the language field is added to.
+   *   The table the field is added to.
    * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
    *   The field definition.
    * @param array $views_field