MDL-53176 grades: Adding index to improve history search

Backport of MDL-50385

lib/db/install.xml

@@ -1918,6 +1918,7 @@
       <INDEXES>
         <INDEX NAME="action" UNIQUE="false" FIELDS="action" COMMENT="insert/update/delete"/>
         <INDEX NAME="timemodified" UNIQUE="false" FIELDS="timemodified"/>
+        <INDEX NAME="userid-itemid-timemodified" UNIQUE="false" FIELDS="userid, itemid, timemodified" COMMENT="Improve history searching"/>
       </INDEXES>
     </TABLE>
     <TABLE NAME="grade_import_newitem" COMMENT="temporary table for storing new grade_item names from grade import">

lib/db/upgrade.php

@@ -4488,5 +4488,22 @@ function xmldb_main_upgrade($oldversion) {
         upgrade_main_savepoint(true, 2015051104.07);
     }
 
+    if ($oldversion < 2015051104.12) {
+        // This could take a long time. Unfortunately, no way to know how long, and no way to do progress, so setting for 1 hour.
+        upgrade_set_timeout(3600);
+
+        // Define index userid-itemid (not unique) to be added to grade_grades_history.
+        $table = new xmldb_table('grade_grades_history');
+        $index = new xmldb_index('userid-itemid-timemodified', XMLDB_INDEX_NOTUNIQUE, array('userid', 'itemid', 'timemodified'));
+
+        // Conditionally launch add index userid-itemid.
+        if (!$dbman->index_exists($table, $index)) {
+            $dbman->add_index($table, $index);
+        }
+
+        // Main savepoint reached.
+        upgrade_main_savepoint(true, 2015051104.09);
+    }
+
     return true;
 }

version.php

@@ -29,7 +29,7 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$version  = 2015051104.11;              // 20150511      = branching date YYYYMMDD - do not modify!
+$version  = 2015051104.12;              // 20150511      = branching date YYYYMMDD - do not modify!
                                         //         RR    = release increments - 00 in DEV branches.
                                         //           .XX = incremental changes.