D11828: Simplify orPostingIterator and make it faster

[Stefan Brüns]

bruns added a comment.


  In D11828#242372 <https://phabricator.kde.org/D11828#242372>, @michaelh wrote:
  
  > While reading in IDE realized `(*it)` resolves to `PostingIterator**` I got a little dizzy at first, then started to play with this code and came up with this.
  >  In Constructor:
  >
  >   for (PostingIterator* it : m_iterators) {
  >     if (it == nullptr) {
  >       m_iterators.erase(&it);
  
  
  Thats not how QVector<>::iterator works
  
  - you can not create an QVector<>::iterator from an PostingIterator*. The latter is just a (pointer to) a PostingIterator, it does not know about the container (QVector) it is member of [1]
  - deleting an element from a container using `.erase(it)` typically invalidates the `it`, thats the reason `.erase(it)` returns an iterator to the next element
  - `it = m_iterators.erase(it)` thus implicitly moves the iterator forward
  
  >    } else {
  >      auto docId = it->next();
  >      if (docId && (docId < m_nextId || m_nextId == 0)) {
  >        m_nextId = docId;
  >      }
  >   }
  > 
  > }
  > 
  >   In `OrPostingIterator::next()`
  
  does not work for the same reason ...
  
  What could work is deleting the PostingIterator immediately and setting the iterator value to `nullptr`, and then do a cleanup pass afterwards with `QVector<>::removeAll(nullptr)`.

REPOSITORY
  R293 Baloo

REVISION DETAIL
  https://phabricator.kde.org/D11828

To: bruns, #baloo, michaelh
Cc: #frameworks, ashaposhnikov, michaelh, astippich, spoorun, ngraham, bruns, alexeymin
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