Allow disabling the MySQL/MariaDB query optimizer for history queries

Some versions of these RDBMS perform poorly with history queries, particularly
when the optimizer changes join order or uses block nested loop joins. Ideally,
testing across all RDBMS versions to identify when the optimizer fails and
adjusting queries or using optimizer switches would be preferable, but this
level of effort is not justified at the moment.

Optimizer is disabled via config:

`/etc/icingaweb2/modules/icingadb/config.ini`:

```
[icingadb]
...
disable_optimizer_for_history_queries=1
```

Author: lippserd

application/controllers/HistoryController.php

@@ -6,9 +6,10 @@
 
 use GuzzleHttp\Psr7\ServerRequest;
 use Icinga\Module\Icingadb\Model\History;
+use Icinga\Module\Icingadb\Util\OptimizerHints;
 use Icinga\Module\Icingadb\Web\Control\SearchBar\ObjectSuggestions;
-use Icinga\Module\Icingadb\Web\Controller;
 use Icinga\Module\Icingadb\Web\Control\ViewModeSwitcher;
+use Icinga\Module\Icingadb\Web\Controller;
 use Icinga\Module\Icingadb\Widget\ItemList\LoadMoreObjectList;
 use ipl\Stdlib\Filter;
 use ipl\Web\Control\LimitControl;
@@ -87,6 +88,10 @@ public function indexAction()
             Filter::like('service.id', '*')
         ));
 
+        if (OptimizerHints::shouldDisableOptimizerForHistoryQueries()) {
+            OptimizerHints::disableOptimizer($history);
+        }
+
         yield $this->export($history);
 
         $this->addControl($sortControl);

application/controllers/HostController.php

@@ -5,6 +5,7 @@
 namespace Icinga\Module\Icingadb\Controllers;
 
 use ArrayIterator;
+use Generator;
 use Icinga\Exception\NotFoundError;
 use Icinga\Module\Icingadb\Command\Object\GetObjectCommand;
 use Icinga\Module\Icingadb\Command\Transport\CommandTransport;
@@ -20,6 +21,7 @@
 use Icinga\Module\Icingadb\Model\Service;
 use Icinga\Module\Icingadb\Model\ServicestateSummary;
 use Icinga\Module\Icingadb\Redis\VolatileStateResults;
+use Icinga\Module\Icingadb\Util\OptimizerHints;
 use Icinga\Module\Icingadb\Web\Control\SearchBar\ObjectSuggestions;
 use Icinga\Module\Icingadb\Web\Control\ViewModeSwitcher;
 use Icinga\Module\Icingadb\Web\Controller;
@@ -38,7 +40,6 @@
 use ipl\Web\Control\SortControl;
 use ipl\Web\Url;
 use ipl\Web\Widget\Tabs;
-use Generator;
 
 class HostController extends Controller
 {
@@ -163,6 +164,10 @@ public function historyAction(): Generator
 
         $history->filter(Filter::lessThanOrEqual('event_time', $before));
 
+        if (OptimizerHints::shouldDisableOptimizerForHistoryQueries()) {
+            OptimizerHints::disableOptimizer($history);
+        }
+
         yield $this->export($history);
 
         $this->addControl($sortControl);

application/controllers/NotificationsController.php

@@ -6,10 +6,11 @@
 
 use GuzzleHttp\Psr7\ServerRequest;
 use Icinga\Module\Icingadb\Model\NotificationHistory;
+use Icinga\Module\Icingadb\Util\OptimizerHints;
 use Icinga\Module\Icingadb\Web\Control\SearchBar\ObjectSuggestions;
+use Icinga\Module\Icingadb\Web\Control\ViewModeSwitcher;
 use Icinga\Module\Icingadb\Web\Controller;
 use Icinga\Module\Icingadb\Widget\ItemList\LoadMoreObjectList;
-use Icinga\Module\Icingadb\Web\Control\ViewModeSwitcher;
 use ipl\Stdlib\Filter;
 use ipl\Web\Control\LimitControl;
 use ipl\Web\Control\SortControl;
@@ -81,6 +82,10 @@ public function indexAction()
             Filter::like('history.service.id', '*')
         ));
 
+        if (OptimizerHints::shouldDisableOptimizerForHistoryQueries()) {
+            OptimizerHints::disableOptimizer($notifications);
+        }
+
         yield $this->export($notifications);
 
         $this->addControl($sortControl);

application/controllers/ServiceController.php

@@ -5,6 +5,7 @@
 namespace Icinga\Module\Icingadb\Controllers;
 
 use ArrayIterator;
+use Generator;
 use Icinga\Exception\NotFoundError;
 use Icinga\Module\Icingadb\Command\Object\GetObjectCommand;
 use Icinga\Module\Icingadb\Command\Transport\CommandTransport;
@@ -17,6 +18,7 @@
 use Icinga\Module\Icingadb\Model\History;
 use Icinga\Module\Icingadb\Model\Service;
 use Icinga\Module\Icingadb\Redis\VolatileStateResults;
+use Icinga\Module\Icingadb\Util\OptimizerHints;
 use Icinga\Module\Icingadb\Web\Control\SearchBar\ObjectSuggestions;
 use Icinga\Module\Icingadb\Web\Control\ViewModeSwitcher;
 use Icinga\Module\Icingadb\Web\Controller;
@@ -34,7 +36,6 @@
 use ipl\Web\Control\SortControl;
 use ipl\Web\Url;
 use ipl\Web\Widget\Tabs;
-use Generator;
 
 class ServiceController extends Controller
 {
@@ -311,6 +312,10 @@ public function historyAction(): Generator
 
         $history->filter(Filter::lessThanOrEqual('event_time', $before));
 
+        if (OptimizerHints::shouldDisableOptimizerForHistoryQueries()) {
+            OptimizerHints::disableOptimizer($history);
+        }
+
         yield $this->export($history);
 
         $this->addControl($sortControl);

library/Icingadb/Util/OptimizerHints.php

@@ -0,0 +1,86 @@
+<?php
+
+namespace Icinga\Module\Icingadb\Util;
+
+use Icinga\Application\Config;
+use ipl\Orm\Query;
+use ipl\Sql\Adapter\Mysql;
+use ipl\Sql\Select;
+use ipl\Stdlib\Str;
+
+/**
+ * Helper class to allow disabling the MySQL/MariaDB query optimizer for history queries.
+ * Some versions of these RDBMS perform poorly with history queries,
+ * particularly when the optimizer changes join order or uses block nested loop joins.
+ * Ideally, testing across all RDBMS versions to identify when the optimizer fails and adjusting queries or
+ * using optimizer switches would be preferable, but this level of effort is not justified at the moment.
+ */
+readonly class OptimizerHints
+{
+    public const DISABLE_OPTIMIZER_HINT = '/*+ NO_BNL() */ STRAIGHT_JOIN';
+
+    /**
+     * Determines whether to disable the query optimizer for history queries.
+     *
+     * Call this method before using {@see disableOptimizer()} to check if optimizer disabling is necessary:
+     *
+     * ```
+     * if (OptimizerHints::shouldDisableOptimizerForHistoryQueries()) {
+     *     OptimizerHints::disableOptimizer($query);
+     * }
+     * ```
+     *
+     * @return bool
+     */
+    public static function shouldDisableOptimizerForHistoryQueries(): bool
+    {
+        return Config::module('icingadb')->get('icingadb', 'disable_optimizer_for_history_queries', false);
+    }
+
+    /**
+     * Injects an optimizer hint into SELECT queries for a MySQL/MariaDB Query object,
+     * forcing the RDBMS to disable the optimizer.
+     *
+     * Call {@see shouldDisableOptimizerForHistoryQueries()} first to check if this is necessary:
+     *
+     *  ```
+     *  if (OptimizerHints::shouldDisableOptimizerForHistoryQueries()) {
+     *      OptimizerHints::disableOptimizer($query);
+     *  }
+     *  ```
+     *
+     * @param Query $q
+     *
+     * @return void
+     */
+    public static function disableOptimizer(Query $q): void
+    {
+        if ($q->getDb()->getAdapter() instanceof Mysql) {
+            // Locates the first string column, prepends the optimizer hint,
+            // and resets columns to ensure it appears first in the SELECT statement:
+            $q->on(Query::ON_SELECT_ASSEMBLED, static function (Select $select) {
+                $columns = $select->getColumns();
+                foreach ($columns as $alias => $column) {
+                    if (is_string($column)) {
+                        if (Str::startsWith($column, static::DISABLE_OPTIMIZER_HINT)) {
+                            return;
+                        }
+
+                        unset($columns[$alias]);
+                        $select->resetColumns();
+
+                        if (is_int($alias)) {
+                            array_unshift($columns, static::DISABLE_OPTIMIZER_HINT . " $column");
+                        } else {
+                            $columns = [$alias => static::DISABLE_OPTIMIZER_HINT . " $column"] + $columns;
+                        }
+
+                        $select->resetColumns()->columns($columns);
+
+                        return;
+                    }
+                }
+            });
+        }
+    }
+}