fix for MDL-8120, fix for slow override SQL. Please test

diff --git a/lib/accesslib.php b/lib/accesslib.php
index 32f13680228597e7e7556da7540ee3e87ad77a4d..43eb4f674a6fd3ea374dbca1d9af2b9189c81bd2 100755 (executable)
--- a/lib/accesslib.php
+++ b/lib/accesslib.php
@@ -819,7 +819,64 @@ function load_user_capability($capability='', $context = NULL, $userid='') {
             $capabilities[] = $temprecord;
             $rs->MoveNext();
         }
-    }              
+    }
+    
+    /** Yu:the following code is an attempt to speed up capabilities resolving during login
+     * this code has not been tested heavily, so the old working (but possibly slower code) is commented out
+     * please help test if this code is working / runs faster for you. please report bugs asap!
+     * this code only affects overrides. Normal capabilities are not affected
+     */
+    
+    /// 1) quick sql to get all roles assigned to this user
+    if ($roles = get_records_sql("SELECT roleid, roleid
+                                  FROM {$CFG->prefix}role_assignments
+                                  WHERE userid = $userid")) {
+        
+        /// 2) foreach role, pull out all the overrides attached in all contexts
+        foreach ($roles as $trole) {
+            if ($overrides = get_records_sql("SELECT * FROM {$CFG->prefix}role_capabilities rc
+                                            WHERE rc.roleid = $trole->roleid
+                                            AND rc.contextid != $siteinstance->id
+                                            $capsearch")) {
+                
+                /// 3) For each context, we find all parent contexts, and see if it's relevant
+                /// it is relevant if for this role, there's a role assignment in 1 parent context or more
+                foreach ($overrides as $loverride) {
+                    $lcontext = get_context_instance_by_id($loverride->contextid);               
+                    // possible to do some caching in get_parent_contexts too
+                    $lparents = get_parent_contexts($lcontext);      
+                    $lparents[] = $lcontext->id; // add self
+                    
+                    /// we get all parent contexts, loop them
+                    foreach ($lparents as $lparent) { 
+                        
+                        /// if we can find a matching pair of contexts(override/assignment)
+                        /// it's possible to do some optimization here to use results obtained in 1)
+                        if ($rp = get_record_sql ("SELECT ra.id, ra.id FROM {$CFG->prefix}role_assignments ra
+                                                   WHERE ra.userid = $userid
+                                                   AND ra.contextid = $lparent
+                                                   AND ra.roleid = $trole->roleid                       
+                                                   $timesql")) {                                 
+                                                     
+                            $llparent = get_context_instance_by_id($lparent);
+                            $lloverride = get_context_instance_by_id($loverride->contextid);
+                            
+                            $temprec = new object();
+                            $temprec->capability = $loverride->capability;  
+                            $temprec->contextlevel = $llparent->contextlevel * 100 + $lloverride ->contextlevel;
+                            $temprec->id2 = $lcontext->id;
+                            $temprec->sum = $loverride->permission;
+                            
+                            /// add to the array for processing
+                            $capabilities[] = $temprec;
+                        }                     
+                    }
+                }
+            }
+        }
+    }
+ 
+    /*  
     // SQL for overrides
     // this is take out because we have no way of making sure c1 is indeed related to c2 (parent)
     // if we do not group by sum, it is possible to have multiple records of rc.capability, c1.id, c2.id, tuple having
@@ -872,7 +929,7 @@ function load_user_capability($capability='', $context = NULL, $userid='') {
             $rs->MoveNext();
         }
     }
-    
+    */
     // this step sorts capabilities according to the contextlevel
     // it is very important because the order matters when we 
     // go through each capabilities later. (i.e. higher level contextlevel