SqlContentEntityStorageSchema::createSharedTableSchema

protected SqlContentEntityStorageSchema::createSharedTableSchema(FieldStorageDefinitionInterface $storage_definition, $only_save = FALSE)

protected function createSharedTableSchema(FieldStorageDefinitionInterface $storage_definition, $only_save = FALSE) {
  $created_field_name = $storage_definition->getName();
  $table_mapping = $this->storage->getTableMapping();
  $column_names = $table_mapping->getColumnNames($created_field_name);
  $schema_handler = $this->database->schema();
  $shared_table_names = array_diff($table_mapping->getTableNames(), $table_mapping->getDedicatedTableNames());

  // Iterate over the mapped table to find the ones that will host the created
  // field schema.
  $schema = array();
  foreach ($shared_table_names as $table_name) {
    foreach ($table_mapping->getFieldNames($table_name) as $field_name) {
      if ($field_name == $created_field_name) {
        // Create field columns.
        $schema[$table_name] = $this->getSharedTableFieldSchema($storage_definition, $table_name, $column_names);
        if (!$only_save) {
          foreach ($schema[$table_name]['fields'] as $name => $specifier) {
            // Check if the field exists because it might already have been
            // created as part of the earlier entity type update event.
            if (!$schema_handler->fieldExists($table_name, $name)) {
              $schema_handler->addField($table_name, $name, $specifier);
            }
          }
          if (!empty($schema[$table_name]['indexes'])) {
            foreach ($schema[$table_name]['indexes'] as $name => $specifier) {
              // Check if the index exists because it might already have been
              // created as part of the earlier entity type update event.
              $this->addIndex($table_name, $name, $specifier, $schema[$table_name]);
            }
          }
          if (!empty($schema[$table_name]['unique keys'])) {
            foreach ($schema[$table_name]['unique keys'] as $name => $specifier) {
              $schema_handler->addUniqueKey($table_name, $name, $specifier);
            }
          }
        }
        // After creating the field schema skip to the next table.
        break;
      }
    }
  }

  $this->saveFieldSchemaData($storage_definition, $schema);

  if (!$only_save) {
    // Make sure any entity index involving this field is re-created if
    // needed.
    $this->createEntitySchemaIndexes($this->getEntitySchema($this->entityType), $storage_definition);
  }
}