[#3349] Prevent race condition in profile view creation.

The only reliable way to prevent it is a condition on the database. In postgres, we add a unique constraint on views with type = 'profile'. MySQL doesn't support this, so we do nothing.

htdocs/lib/db/upgrade.php

@@ -885,6 +885,48 @@ function xmldb_core_upgrade($oldversion=0) {
         };
     }
 
+    if ($oldversion < 2009022619) {
+        // Delete duplicate profile views if there are any, then add an index
+        // that will prevent it happening again - but only on postgres, as it's
+        // the only db that supports partial indexes
+        if ($viewdata = get_records_sql_array("
+            SELECT owner, id
+            FROM {view}
+            WHERE owner IN (
+                SELECT owner
+                FROM {view}
+                WHERE type = 'profile'
+                GROUP BY owner
+                HAVING COUNT(*) > 1
+            )
+            AND type = 'profile'
+            ORDER BY owner, id", array())) {
+
+            require_once('view.php');
+            $seen = array();
+            foreach ($viewdata as $record) {
+                $seen[$record->owner][] = $record->id;
+            }
+
+            foreach ($seen as $owner => $views) {
+                // Remove the first one, which is their real profile view
+                array_shift($views);
+                foreach ($views as $viewid) {
+                    $view = new View($viewid);
+                    if ($view->get('type') == 'profile') {
+                        $view->delete();
+                    }
+                    else {
+                        log_info("Odd: upgrade to delete duplicate profile views tried to delete a normal view? (id=$viewid)");
+                    }
+                }
+            }
+        }
+        if (is_postgres()) {
+            execute_sql("CREATE UNIQUE INDEX {view_own_type_uix} ON {view}(owner) WHERE type = 'profile'");
+        }
+    }
+
     return $status;
 
 }

htdocs/lib/upgrade.php

@@ -548,11 +548,14 @@ function core_postinst() {
     set_config('installation_key', get_random_key());
 
     // PostgreSQL supports indexes over functions of columns, MySQL does not. 
-    // So we can improve the index on the username field of the usr table for 
-    // Postgres
+    // We make use if this if we can
     if (is_postgres()) {
+        // Improve the username index
         execute_sql('DROP INDEX {usr_use_uix}');
         execute_sql('CREATE UNIQUE INDEX {usr_use_uix} ON {usr}(LOWER(username))');
+
+        // Only one profile view per user
+        execute_sql("CREATE UNIQUE INDEX {view_own_type_uix} ON {view}(owner) WHERE type = 'profile'");
     }
 
     // Some more advanced constraints. XMLDB can't handle this in its xml file format