From 17b0efae11390b6aabc387e2c8a618ac81d28bfa Mon Sep 17 00:00:00 2001
From: martinlanghoff <martinlanghoff>
Date: Wed, 19 Sep 2007 06:50:53 +0000
Subject: [PATCH] accesslib: Introducing cleanup_contexts() and use it in cron

The newly minted cleanup_contexts() walks the context table
matching contexts with the tables they are referencing and
clearing any leftover contexts.
---
 admin/cron.php    |  3 ++
 lib/accesslib.php | 72 +++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/admin/cron.php b/admin/cron.php
index d001e2e807..c9e7b57939 100644
--- a/admin/cron.php
+++ b/admin/cron.php
@@ -368,6 +368,9 @@
         unset($authplugin);
     }
 
+    // Accesslib stuff
+    cleanup_contexts();
+
     if (!empty($CFG->enablestats) and empty($CFG->disablestatsprocessing)) {
 
         // check we're not before our runtime
diff --git a/lib/accesslib.php b/lib/accesslib.php
index f99242300d..7321ffb83b 100755
--- a/lib/accesslib.php
+++ b/lib/accesslib.php
@@ -1780,11 +1780,11 @@ function create_system_context() {
     }
 }
 /**
- * Create a new context record for use by all roles-related stuff
+ * Remove a context record and any dependent entries
  * @param $level
  * @param $instanceid
  *
- * @return true if properly deleted
+ * @return bool properly deleted
  */
 function delete_context($contextlevel, $instanceid) {
     if ($context = get_context_instance($contextlevel, $instanceid)) {
@@ -1797,6 +1797,74 @@ function delete_context($contextlevel, $instanceid) {
     return true;
 }
 
+/**
+ * Remove stale context records
+ *
+ * @return bool
+ */
+function cleanup_contexts() {
+    global $CFG;
+
+    $sql = "  SELECT " . CONTEXT_COURSECAT . " AS level,
+                     c.instanceid AS instanceid
+              FROM {$CFG->prefix}context c
+              LEFT OUTER JOIN {$CFG->prefix}course_categories AS t
+                ON c.instanceid = t.id
+              WHERE t.id IS NULL AND c.contextlevel = " . CONTEXT_COURSECAT . "
+            UNION
+              SELECT " . CONTEXT_COURSE . " AS level,
+                     c.instanceid AS instanceid
+              FROM {$CFG->prefix}context c
+              LEFT OUTER JOIN {$CFG->prefix}course AS t
+                ON c.instanceid = t.id
+              WHERE t.id IS NULL AND c.contextlevel = " . CONTEXT_COURSE . "
+            UNION
+              SELECT " . CONTEXT_MODULE . " AS level,
+                     c.instanceid AS instanceid
+              FROM {$CFG->prefix}context c
+              LEFT OUTER JOIN {$CFG->prefix}course_modules AS t
+                ON c.instanceid = t.id
+              WHERE t.id IS NULL AND c.contextlevel = " . CONTEXT_MODULE . "
+            UNION
+              SELECT " . CONTEXT_USER . " AS level,
+                     c.instanceid AS instanceid
+              FROM {$CFG->prefix}context c
+              LEFT OUTER JOIN {$CFG->prefix}user AS t
+                ON c.instanceid = t.id
+              WHERE t.id IS NULL AND c.contextlevel = " . CONTEXT_USER . "
+            UNION
+              SELECT " . CONTEXT_BLOCK . " AS level,
+                     c.instanceid AS instanceid
+              FROM {$CFG->prefix}context c
+              LEFT OUTER JOIN {$CFG->prefix}block_instance AS t
+                ON c.instanceid = t.id
+              WHERE t.id IS NULL AND c.contextlevel = " . CONTEXT_BLOCK . "
+            UNION
+              SELECT " . CONTEXT_GROUP . " AS level,
+                     c.instanceid AS instanceid
+              FROM {$CFG->prefix}context c
+              LEFT OUTER JOIN {$CFG->prefix}groups AS t
+                ON c.instanceid = t.id
+              WHERE t.id IS NULL AND c.contextlevel = " . CONTEXT_GROUP . "
+           ";
+    $rs = get_recordset_sql($sql);
+    if ($rs->RecordCount()) {
+        begin_sql();
+        $tx = true;
+        while ($tx && $ctx = rs_fetch_next_record($rs)) {
+            $tx = $tx && delete_context($ctx->level, $ctx->instanceid);
+        }
+        rs_close($rs);
+        if ($tx) {
+            commit_sql();
+            return true;
+        }
+        rollback_sql();
+        return false;
+    }
+    return true;
+}
+
 /**
  * Validate that object with instanceid really exists in given context level.
  *
-- 
2.39.5