Re: [Boost-users] [MultIndex] Iterator/Range validity when modify entries.

Subject: Re: [Boost-users] [MultIndex] Iterator/Range validity when modify entries.
From: Deniz Bahadir (dbahadir_at_[hidden])
Date: 2016-09-09 04:23:04

Am 08.09.2016 um 21:06 schrieb Joaquin M López Muñoz:
> El 08/09/2016 a las 19:17, Deniz Bahadir escribió:
>> Am 08.09.2016 um 18:39 schrieb Joaquin M López Muñoz:
>>> El 08/09/2016 a las 18:22, Deniz Bahadir escribió:
>> So, just to make sure:
>> This second solution would even work if Index2 is unique and I have a
>> collision with key2 (as my example code would definitively have)?
>
> Correct. The only thing you have to be careful about is not to touch key1,
> as the element would be repositioned (according to the order of Index1) and
> your iterator would end up somewhere else within/outside the range.
>
>> However, the side effect would be, that I end up erasing all elements of
>> my range except for the first? (Or even erasing that first element, too,
>> if the database already contains another element outside my range with
>> that same value for key2.)
>
> Yes, if your changing the key produces a collision, the element is erased.
> Depending on your use case, you might want to consider other approaches:
>
>   -  replace() is passed a new element rather than let you change the
> existing
>   one: if a collision would ensue, replace() does not change the
> original element.
>   - There is a rollback-equipped version of modify() where you can undo
>   collision-producing changes.
>
> Joaquín M López Muñoz

Thank you very much, Joaquín.
This helps a lot.

Deniz