Vyřešení zpomalení v MySQL kvůli vysokým offsetům podle https://stack…

…overflow.com/a/16935313/4837606

src/QueryBuilderFetcher.php

@@ -2,23 +2,107 @@
 
 namespace ADT\BulkFetcher;
 
+use App\Utils;
+use Kdyby\Doctrine\Dql\InlineParamsBuilder;
+use Kdyby\Doctrine\NativeQueryBuilder;
+
+/**
+ * Vyřešení zpomalení v MySQL kvůli vysokým offsetům podle https://stackoverflow.com/a/16935313/4837606
+ */
 class QueryBuilderFetcher extends AbstractFetcher {
 
-	/** @var \Doctrine\ORM\QueryBuilder */
+	/** @var NativeQueryBuilder|InlineParamsBuilder */
 	protected $qb;
 
-	public function __construct($qb, $batch = 100) {
+	/** @var array */
+	protected $lastRowData = NULL;
+
+	/** @var string */
+	protected $entityIdentifierColumn = NULL;
+
+	/** @var array */
+	protected $queryHints = [];
+
+	public function setHint($name, $value)
+	{
+		$this->queryHints[$name] = $value;
+		return $this;
+	}
+
+	/**
+	 * QueryBuilderFetcher constructor.
+	 * @param int $qb
+	 * @param int $batch
+	 * @param string $entityIdentifierColumn
+	 */
+	public function __construct($qb, $batch = 100, $entityIdentifierColumn = 'e.id') {
 		parent::__construct($batch);
 
 		$this->qb = $qb;
+		$this->entityIdentifierColumn = $entityIdentifierColumn;
+
+		$this->lastRowData = [
+			$this->entityIdentifierColumn => 0,
+		];
+
+		$this->qb->andWhere("{$this->entityIdentifierColumn} > :".static::param($this->entityIdentifierColumn));
+
+		$this->qb->addOrderBy("{$this->entityIdentifierColumn}", 'ASC');
 	}
 
 	protected function loadNewData() {
-		return $this->qb
-			->getQuery()
-			->setFirstResult($this->offset)
+
+		foreach ($this->lastRowData as $columnName => $value) {
+			$this->qb->setParameter(static::param($columnName), $value);
+		}
+
+		$query = $this->qb
+			->getQuery();
+
+		foreach ($this->queryHints as $name => $value) {
+			$query->setHint($name, $value);
+		}
+
+		$data = $query
+			->setFirstResult(0)
 			->setMaxResults($this->limit)
 			->getResult();
+
+		if (!count($data)) {
+			return $data;
+		}
+
+		$lastRow = $data[count($data)-1];
+
+
+		if (!is_object($lastRow)) {
+			// Doctrine vrací objekt na indexu 0
+			$lastRow = $lastRow[0]; // TODO: možnost nastavit si callback, který vrátí atribut (viz dále)
+		}
+
+		foreach (array_keys($this->lastRowData) as $columnName) {
+			// TODO: možnost nastavit si callback, který vrátí atribut, protože to nemusí být pole objektů
+
+			$rootEntityAlias = substr($this->entityIdentifierColumn, 0, strpos($this->entityIdentifierColumn, '.'));    // "e.id" -> "e"
+			$propertyName = str_replace(
+				'.',
+				'->',
+				strpos($columnName, $rootEntityAlias.'.') === 0
+					? substr($columnName, strpos($columnName, '.') + 1) // "e.column1" -> "column1"
+					: $columnName
+			);
+
+			$this->lastRowData[$columnName] = Utils::accessNestedObjectPropertyByString($propertyName, $lastRow);
+		}
+
+
+		return $data;
+	}
+
+	protected static function param($param)
+	{
+		// TODO: možnost nastavit si název parametru, aby náhodou nekolidoval
+		return 'QueryBuilderFetcher_' . str_replace('.', '__', $param);
 	}
 
 }