Releted() query count

[PetrHudik]

I've noticed some performance issues in v. 2.3.5, so I've written failing test. This test is passing in v. 2.3.4. This little bug kills my app really badly.

I don't underestant what is under the hood Nette/Database, I've spent a lot of time isolating this issue and this test explains is quite well.

Should I create an Issue? or is failing test enought?

[Unlink]

I know, where a problem is.
It is caused by this commit 1c7eba6.
If you remove ->where('state', 'private') it works how you expected and 3 queries are used. But when you use where, limit, group..., it now clear also referenced cache.

I think, that it couldn't invalidate data, if query paramaters wasn't changed.
So it can be implement like this

public function limit($limit, $offset = NULL)
{
    $oldKey = $this->getSpecificCacheKey();
    $this->sqlBuilder->setLimit($limit, $offset);
    if ($oldKey != $this->getSpecificCacheKey()) {
        $this->emptyResultSet();
    }
    return $this;
}

or find another way, how to invalidate referenced data because in that case it also makes lot of queries

foreach ($context->table('book') as $book) {
    foreach ($book->related('book_tag_alt')->where('state', ($book->id % 2) ? 'private' : 'public') as $bookTag) {
        $tag = $bookTag->tag;
    }
}

But this is not good example, because before 1c7eba6 it also use 1 + n + 2 queries and now 1 + 2n

[Unlink]

ping @Hajneej

[Hajneej]

@Unlink @PetrHudik send PR #92 solved by clearing cache only for root selection, not for GroupedSelection