Search not finding search term from page title

Question

Using the default database search index in drupal 8, when I search for a term from the a page title, sometimes it shows the result and sometimes it shows nothing, even though i enter the exact page title in the search. All pages have been indexed.

How can I debug why the search term is not being returned?

Answer 1

This is easy to debug, because the search index is built of rendered nodes with the view mode search_index. So you could build a view displaying all nodes with this view mode and check the result:

Edit:

The node search plugin adds the title to the rendered node, so if the page title is the node label, it should be included in the search index:

NodeSearch::updateIndex():

  $build = $node_render->view($node, 'search_index', $language->getId());
  ...
  // Add the title to text so it is searchable.
  $build['search_title'] = [
    '#prefix' => '<h1>',
    '#plain_text' => $node->label(),
    '#suffix' => '</h1>',
    '#weight' => -1000
  ];
  $text = $this->renderer->renderPlain($build);