diff --git a/core/modules/node/lib/Drupal/node/Plugin/Search/NodeSearch.php b/core/modules/node/lib/Drupal/node/Plugin/Search/NodeSearch.php
index 560c772..a2064a5 100644
--- a/core/modules/node/lib/Drupal/node/Plugin/Search/NodeSearch.php
+++ b/core/modules/node/lib/Drupal/node/Plugin/Search/NodeSearch.php
@@ -79,7 +79,7 @@ class NodeSearch extends SearchPluginBase implements AccessibleInterface, Search
 
   /**
    * The list of options and info for advanced search filters.
-   * 
+   *
    * Each entry in the array has the option as key and and info array that
    * determines how the value is matched in the databse query. The possible keys
    * in the info array are:
@@ -87,14 +87,14 @@ class NodeSearch extends SearchPluginBase implements AccessibleInterface, Search
    *  - join: (optional) information on a table to join.  By default the data
    *           is matched against the {node_field_data} table.
    *  - operator: (optional) OR or AND, defaults to OR
-   * 
+   *
    * @var array
    */
   protected $advanced = array(
     'type' => array('column' => 'n.type'),
     'langcode' => array('column' => 'n.langcode'),
     'author' => array('column' => 'n.uid'),
-    'term', array('column' => 'ti.tid', 'join' => array('table' => 'taxonomy_index', 'alias' => 'ti', 'condition' => 'n.nid = ti.nid')),
+    'term' => array('column' => 'ti.tid', 'join' => array('table' => 'taxonomy_index', 'alias' => 'ti', 'condition' => 'n.nid = ti.nid')),
   );
 
   /**
@@ -172,34 +172,30 @@ public function execute() {
        ->addTag('node_access')
        ->searchExpression($keys, $this->getPluginId());
 
+     // Handle advanced search filters in the f query string.
      $parameters = $this->getParameters();
-     // Combine the f query strings into one string to simplify matching by
-     // field and combining each field into one condition clause. The
-     // $parameters['f'] variable is expected to be an array of options and
-     // values separated by a ':' like
-     // array('type:page', 'term:27', 'term:13', 'langcode:en')
-     // so $f is a string of such values like
-     // 'type:page term:27 term:13 langcode:en'
-     // and using preg_match_all() for each option in the pattern collects all
-     // the values that need to be added to a single condition object.
-     $f = !empty($parameters['f']) ? implode(' ', (array) $parameters['f']) : '';
-     if ($f) {
-       $found = array();
-       foreach ($this->advanced as $option => $info) {
-         $matches = array();
-         $pattern = '/(^| )' . $option . ':([^ ]*)( |$)/i';
-         if (preg_match_all($pattern, $f, $matches)) {
-           $found[$option] = $matches[2];
-           // Insert additional conditions. By default, all use the OR operator.
-           $operator = empty($info['operator']) ? 'OR' : $info['operator'];
-           $where = new Condition($operator);
-           foreach ($matches[2] as $value) {
-             $where->condition($info['column'], $value);
-           }
-           $query->condition($where);
-           if (!empty($info['join'])) {
-             $query->join($info['join']['table'], $info['join']['alias'], $info['join']['condition']);
-           }
+     if (!empty($parameters['f']) && is_array($parameters['f'])) {
+       $filters = array();
+       // Match any query value that is an expected option and a value
+       // separated by ':' like 'term:27'.
+       $pattern = '/(' . implode('|', array_keys($this->advanced)) . '):([^ ]*)/i';
+       foreach ($parameters['f'] as $item) {
+         if (preg_match($pattern, $item, $m)) {
+           // Use the matched value as the array key to eliminate duplicates.
+           $filters[$m[1]][$m[2]] = $m[2];
+         }
+       }
+       foreach ($filters as $option => $matched) {
+         $info = $this->advanced[$option];
+         // Insert additional conditions. By default, all use the OR operator.
+         $operator = empty($info['operator']) ? 'OR' : $info['operator'];
+         $where = new Condition($operator);
+         foreach ($matched as $value) {
+           $where->condition($info['column'], $value);
+         }
+         $query->condition($where);
+         if (!empty($info['join'])) {
+           $query->join($info['join']['table'], $info['join']['alias'], $info['join']['condition']);
          }
        }
      }