Put FetchJoin Adapter logic into its own class.

src/DataTables/Adapter/FetchJoinORMAdapter.php

@@ -0,0 +1,145 @@
+<?php
+/**
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ * Copyright (C) 2019 - 2020 Jan Böhmer (https://github.com/jbtronics)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+ */
+
+namespace App\DataTables\Adapter;
+
+use Doctrine\ORM\Query;
+use Doctrine\ORM\QueryBuilder;
+use Doctrine\ORM\Tools\Pagination\Paginator;
+use Omines\DataTablesBundle\Adapter\AdapterQuery;
+use Omines\DataTablesBundle\Adapter\Doctrine\Event\ORMAdapterQueryEvent;
+use Omines\DataTablesBundle\Adapter\Doctrine\ORMAdapterEvents;
+use Omines\DataTablesBundle\Column\AbstractColumn;
+use Symfony\Component\OptionsResolver\OptionsResolver;
+
+/**
+ * Similar to ORMAdapter this class allows to access objects from the doctrine ORM.
+ * Unlike the default ORMAdapter supports Fetch Joins (additional entites are fetched from DB via joins) using
+ * the Doctrine Paginator.
+ * @author Jan Böhmer
+ */
+class FetchJoinORMAdapter extends ORMAdapter
+{
+    protected $use_simple_total;
+
+    public function configure(array $options)
+    {
+        parent::configure($options);
+        $this->use_simple_total = $options['simple_total_query'];
+    }
+
+    protected function configureOptions(OptionsResolver $resolver)
+    {
+        parent::configureOptions($resolver);
+
+        //Enforce object hydration mode (fetch join only works for objects)
+        $resolver->addAllowedValues('hydrate', Query::HYDRATE_OBJECT);
+
+        /**
+         * Add the possibility to replace the query for total entity count through a very simple one, to improve performance.
+         * You can only use this option, if you did not apply any criteria to your total count.
+         */
+        $resolver->setDefault('simple_total_query', false);
+
+        return $resolver;
+    }
+
+    protected function prepareQuery(AdapterQuery $query)
+    {
+        $state = $query->getState();
+        $query->set('qb', $builder = $this->createQueryBuilder($state));
+        $query->set('rootAlias', $rootAlias = $builder->getDQLPart('from')[0]->getAlias());
+
+        // Provide default field mappings if needed
+        foreach ($state->getDataTable()->getColumns() as $column) {
+            if (null === $column->getField() && isset($this->metadata->fieldMappings[$name = $column->getName()])) {
+                $column->setOption('field', "{$rootAlias}.{$name}");
+            }
+        }
+
+        /** @var Query\Expr\From $fromClause */
+        $fromClause = $builder->getDQLPart('from')[0];
+        $identifier = "{$fromClause->getAlias()}.{$this->metadata->getSingleIdentifierFieldName()}";
+
+        //Use simpler (faster) total count query if the user wanted so...
+        if ($this->use_simple_total) {
+            $query->setTotalRows($this->getSimpleTotalCount($builder));
+        } else {
+            $query->setTotalRows($this->getCount($builder, $identifier));
+        }
+
+        // Get record count after filtering
+        $this->buildCriteria($builder, $state);
+        $query->setFilteredRows($this->getCount($builder, $identifier));
+
+        // Perform mapping of all referred fields and implied fields
+        $aliases = $this->getAliases($query);
+        $query->set('aliases', $aliases);
+        $query->setIdentifierPropertyPath($this->mapFieldToPropertyPath($identifier, $aliases));
+    }
+
+    public function getResults(AdapterQuery $query): \Traversable
+    {
+        $builder = $query->get('qb');
+        $state = $query->getState();
+
+        // Apply definitive view state for current 'page' of the table
+        foreach ($state->getOrderBy() as list($column, $direction)) {
+            /** @var AbstractColumn $column */
+            if ($column->isOrderable()) {
+                $builder->addOrderBy($column->getOrderField(), $direction);
+            }
+        }
+        if ($state->getLength() > 0) {
+            $builder
+                ->setFirstResult($state->getStart())
+                ->setMaxResults($state->getLength());
+        }
+
+        $query = $builder->getQuery();
+        $event = new ORMAdapterQueryEvent($query);
+        $state->getDataTable()->getEventDispatcher()->dispatch($event, ORMAdapterEvents::PRE_QUERY);
+
+        //Use Doctrine paginator for result iteration
+        $paginator = new Paginator($query);
+
+        foreach ($paginator->getIterator() as $result) {
+            yield $result;
+            $this->manager->detach($result);
+        }
+    }
+
+    public function getCount(QueryBuilder $queryBuilder, $identifier)
+    {
+        $paginator = new Paginator($queryBuilder);
+        return $paginator->count();
+    }
+
+    protected function getSimpleTotalCount(QueryBuilder $queryBuilder)
+    {
+        /** The paginator count queries can be rather slow, so when query for total count (100ms or longer),
+         * just return the entity count.
+         */
+        /** @var Query\Expr\From $from_expr */
+        $from_expr = $queryBuilder->getDQLPart('from')[0];
+        return $this->manager->getRepository($from_expr->getFrom())->count([]);
+    }
+}