MDL-74912 mod_forum: Fix regexp word boundaries markers in MySQL 8

lib/dml/moodle_database.php

@@ -2483,6 +2483,30 @@ abstract class moodle_database {
         return '';
     }
 
+    /**
+     * Returns the word-beginning boundary marker if this database driver supports regex syntax when searching.
+     * @return string The word-beginning boundary marker. Otherwise, an empty string.
+     */
+    public function sql_regex_get_word_beginning_boundary_marker() {
+        if ($this->sql_regex_supported()) {
+            return '[[:<:]]';
+        }
+
+        return '';
+    }
+
+    /**
+     * Returns the word-end boundary marker if this database driver supports regex syntax when searching.
+     * @return string The word-end boundary marker. Otherwise, an empty string.
+     */
+    public function sql_regex_get_word_end_boundary_marker() {
+        if ($this->sql_regex_supported()) {
+            return '[[:>:]]';
+        }
+
+        return '';
+    }
+
     /**
      * Returns the SQL that allows to find intersection of two or more queries
      *

lib/dml/mysqli_native_moodle_database.php

@@ -1876,6 +1876,38 @@ class mysqli_native_moodle_database extends moodle_database {
         return $collation . ($positivematch ? 'REGEXP' : 'NOT REGEXP');
     }
 
+    /**
+     * Returns the word-beginning boundary marker based on MySQL version.
+     * @return string The word-beginning boundary marker.
+     */
+    public function sql_regex_get_word_beginning_boundary_marker() {
+        $ismysql = ($this->get_dbtype() == 'mysqli' || $this->get_dbtype() == 'auroramysql');
+        $ismysqlge8d0d4 = ($ismysql && version_compare($this->get_server_info()['version'], '8.0.4', '>='));
+        if ($ismysqlge8d0d4) {
+            return '\\b';
+        }
+        // Prior to MySQL 8.0.4, MySQL used the Henry Spencer regular expression library to support regular expression operations,
+        // rather than International Components for Unicode (ICU).
+        // MariaDB still supports the "old marker" (MDEV-5357).
+        return '[[:<:]]';
+    }
+
+    /**
+     * Returns the word-end boundary marker based on MySQL version.
+     * @return string The word-end boundary marker.
+     */
+    public function sql_regex_get_word_end_boundary_marker() {
+        $ismysql = ($this->get_dbtype() == 'mysqli' || $this->get_dbtype() == 'auroramysql');
+        $ismysqlge8d0d4 = ($ismysql && version_compare($this->get_server_info()['version'], '8.0.4', '>='));
+        if ($ismysqlge8d0d4) {
+            return '\\b';
+        }
+        // Prior to MySQL 8.0.4, MySQL used the Henry Spencer regular expression library to support regular expression operations,
+        // rather than International Components for Unicode (ICU).
+        // MariaDB still supports the "old marker" (MDEV-5357).
+        return '[[:>:]]';
+    }
+
     /**
      * Returns the SQL to be used in order to an UNSIGNED INTEGER column to SIGNED.
      *

lib/searchlib.php

@@ -418,6 +418,8 @@ function search_generate_SQL($parsetree, $datafield, $metafield, $mainidfield, $
     if ($DB->sql_regex_supported()) {
         $REGEXP    = $DB->sql_regex(true);
         $NOTREGEXP = $DB->sql_regex(false);
+        $regexwordbegin = $DB->sql_regex_get_word_beginning_boundary_marker();
+        $regexwordend = $DB->sql_regex_get_word_end_boundary_marker();
     }
 
     $params = array();
@@ -456,8 +458,8 @@ function search_generate_SQL($parsetree, $datafield, $metafield, $mainidfield, $
                 break;
             case TOKEN_EXACT:
                 $SQLString .= "(($datafield $REGEXP :$name1) OR ($metafield $REGEXP :$name2))";
-                $params[$name1] =  "[[:<:]]".$value."[[:>:]]";
-                $params[$name2] =  "[[:<:]]".$value."[[:>:]]";
+                $params[$name1] =  $regexwordbegin.$value.$regexwordend;
+                $params[$name2] =  $regexwordbegin.$value.$regexwordend;
                 break;
             case TOKEN_META:
                 if ($metafield != '') {

lib/upgrade.txt

@@ -1,6 +1,10 @@
 This files describes API changes in core libraries and APIs,
 information provided here is intended especially for developers.
 
+=== 3.11.11 ===
+* New DML driver methods `$DB->sql_regex_get_word_beginning_boundary_marker` and `$DB->sql_regex_get_word_end_boundary_marker`
+  for managing word boundary markers in a database driver supporting regex syntax when searching.
+
 === 3.11.8 ===
 * The check for $plugin->incompatible was found to be incorrect. The $plugin->incompatible attribute is meant to define the minimum
   Moodle version the plugin is incompatible with but the implemented logic for the check was the opposite. Plugins declaring this