Doctrine2和Iterate时PostLoad事件的危险

Question

在Doctrine2关于事件的文档中说：

Note that, when using Doctrine\ORM\AbstractQuery#iterate(), postLoad events will be executed immediately after objects are being hydrated, and therefore associations are not guaranteed to be initialized. It is not safe to combine usage of Doctrine\ORM\AbstractQuery#iterate() and postLoad event handlers.

为什么不安全？

迭代基本上是在迭代器的基础上对行进行水合，所以我没有区别。

AbstractQuery：

迭代中的

：   $this->_em->newHydrator($this->_hydrationMode)->iterate($stmt, $rsm, $this->_hints);

执行中的

： $this->_em->newHydrator($this->_hydrationMode)->hydrateAll($stmt, $rsm, $this->_hints);

hydrateAllData调用hydrateRowData但生成快照：

    while ($row = $this->_stmt->fetch(PDO::FETCH_ASSOC)) {
        $this->hydrateRowData($row, $result);
    }

    // Take snapshots from all newly initialized collections
    foreach ($this->initializedCollections as $coll) {
        $coll->takeSnapshot();
    }

vs简单的hydrateRow。

关于那些快照吗？