[5.4] Optimize smart search module (#45347)

Smart Search module creates new Query and triggers `Joomla\Component\Finder\Administrator\Indexer::processString()` method which loads available taxonomy branch titles via separate SQL query per each module (duplicate query).

We should not process empty string, when the module is loaded without any input. Plus, `Taxonomy::getBranchTitles()` load should use static cache and produce only single query to prevent duplicate when we have multiple mod_finder instances (i.e. typical case for Yootheme templates where one module is rendered in header and second in mobile dialog).

Author: Denitz

administrator/components/com_finder/src/Indexer/Query.php

@@ -733,8 +733,10 @@ protected function processDates($date1, $date2, $when1, $when2)
      */
     protected function processString($input, $lang, $mode)
     {
-        if ($input === null) {
-            $input = '';
+        $input = trim($input ?? '');
+
+        if ($input === '') {
+            return true;
         }
 
         // Clean up the input string.

administrator/components/com_finder/src/Indexer/Taxonomy.php

@@ -306,23 +306,29 @@ public static function addMap($linkId, $nodeId)
      */
     public static function getBranchTitles()
     {
-        $db = Factory::getDbo();
+        static $titles;
 
-        // Set user variables
-        $groups = implode(',', Factory::getUser()->getAuthorisedViewLevels());
+        if ($titles === null) {
+            $db = Factory::getDbo();
 
-        // Create a query to get the taxonomy branch titles.
-        $query = $db->getQuery(true)
-            ->select($db->quoteName('title'))
-            ->from($db->quoteName('#__finder_taxonomy'))
-            ->where($db->quoteName('parent_id') . ' = 1')
-            ->where($db->quoteName('state') . ' = 1')
-            ->where($db->quoteName('access') . ' IN (' . $groups . ')');
+            // Set user variables
+            $groups = implode(',', Factory::getUser()->getAuthorisedViewLevels());
 
-        // Get the branch titles.
-        $db->setQuery($query);
+            // Create a query to get the taxonomy branch titles.
+            $query = $db->getQuery(true)
+                ->select($db->quoteName('title'))
+                ->from($db->quoteName('#__finder_taxonomy'))
+                ->where($db->quoteName('parent_id') . ' = 1')
+                ->where($db->quoteName('state') . ' = 1')
+                ->where($db->quoteName('access') . ' IN (' . $groups . ')');
+
+            // Get the branch titles.
+            $db->setQuery($query);
+
+            $titles = $db->loadColumn();
+        }
 
-        return $db->loadColumn();
+        return $titles;
     }
 
     /**