Implements hook_field_storage_details().
function field_test_field_storage_details($field) {
$details = array();
// Add field columns.
$columns = array();
foreach ((array) $field['columns'] as $column_name => $attributes) {
$columns[$column_name] = $column_name;
}
return array(
'drupal_variables' => array(
'field_test_storage_data[FIELD_LOAD_CURRENT]' => $columns,
'field_test_storage_data[FIELD_LOAD_REVISION]' => $columns,
),
);
}