From 7994f1c9858dec731ae2a5b849635b08d75d673d Mon Sep 17 00:00:00 2001
From: Tim Hunt <T.J.Hunt@open.ac.uk>
Date: Fri, 17 Feb 2023 15:53:55 +0000
Subject: [PATCH] MDL-75576 quiz statistics: don't time-limit the use of cached
 values

This should have been done as part of  MDL-74762, but was missed.
---
 .../report/statistics/classes/calculator.php  | 19 +++++++++----------
 mod/quiz/report/statistics/upgrade.txt        |  5 +++++
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/mod/quiz/report/statistics/classes/calculator.php b/mod/quiz/report/statistics/classes/calculator.php
index 514669e7087..bc5fe65af7d 100644
--- a/mod/quiz/report/statistics/classes/calculator.php
+++ b/mod/quiz/report/statistics/classes/calculator.php
@@ -121,21 +121,23 @@ class calculator {
         return $quizstats;
     }
 
-    /** @var integer Time after which statistics are automatically recomputed. */
+    /**
+     * @var int Time after which statistics are automatically recomputed.
+     * @deprecated since Moodle 4.3. Use of pre-computed stats is no longer time-limited.
+     * @todo MDL-78091 Final deprecation in Moodle 4.7
+     */
     const TIME_TO_CACHE = 900; // 15 minutes.
 
     /**
      * Load cached statistics from the database.
      *
-     * @param $qubaids \qubaid_condition
+     * @param \qubaid_condition $qubaids
      * @return calculated The statistics for overall attempt scores or false if not cached.
      */
     public function get_cached($qubaids) {
         global $DB;
 
-        $timemodified = time() - self::TIME_TO_CACHE;
-        $fromdb = $DB->get_record_select('quiz_statistics', 'hashcode = ? AND timemodified > ?',
-                                         [$qubaids->get_hash_code(), $timemodified]);
+        $fromdb = $DB->get_record('quiz_statistics', ['hashcode' => $qubaids->get_hash_code()]);
         $stats = new calculated();
         $stats->populate_from_record($fromdb);
         return $stats;
@@ -145,14 +147,11 @@ class calculator {
      * Find time of non-expired statistics in the database.
      *
      * @param $qubaids \qubaid_condition
-     * @return integer|boolean Time of cached record that matches this qubaid_condition or false is non found.
+     * @return int|bool Time of cached record that matches this qubaid_condition or false is non found.
      */
     public function get_last_calculated_time($qubaids) {
         global $DB;
-
-        $timemodified = time() - self::TIME_TO_CACHE;
-        return $DB->get_field_select('quiz_statistics', 'timemodified', 'hashcode = ? AND timemodified > ?',
-                                         [$qubaids->get_hash_code(), $timemodified]);
+        return $DB->get_field('quiz_statistics', 'timemodified', ['hashcode' => $qubaids->get_hash_code()]);
     }
 
     /**
diff --git a/mod/quiz/report/statistics/upgrade.txt b/mod/quiz/report/statistics/upgrade.txt
index 0714629032f..415263c1e10 100644
--- a/mod/quiz/report/statistics/upgrade.txt
+++ b/mod/quiz/report/statistics/upgrade.txt
@@ -7,6 +7,11 @@ information provided here is intended especially for developers.
   (which are really private to the quiz, and not part of any API you should be using) now have a new
   optional argument $calculateifrequired.
 
+* In the past, the methods \quiz_statistics\calculator::get_last_calculated_time() and calculator::get_cached()
+  only returned the pre-computed statistics if they were computed less than 15 minutes ago. Now, they will
+  always return any computed statistics that exist. Therefore, the constant calculator::TIME_TO_CACHE has been
+  deprecated.
+
 
 === 3.2 ===