Re: [Boost-users] [multi_index] modify_key with an iterator to composite_key

Subject: Re: [Boost-users] [multi_index] modify_key with an iterator to composite_key
From: joaquin_at_[hidden]
Date: 2010-01-27 10:29:00

Christian Holmquist escribió:
>
>     On the bright side, index updating has been implemented so as to
>     be as fast
>     as possible: before relocating an element indices check internally
>     whether
>     the element remains in place after modification, which is usually
>     a cheaper
>     operation than brute relocation. In the particular case of a
>     hashed index, if modify()
>     hasn't touched its key then updating merely invokes a hash call
>     and a couple of
>     pointer comparisons (not even equality comparison is needed.)
>
>
> Excellent, this is definitely good enough. Will I gain anything by 
> choosing
> hashed_non_unique over hashed_unique in this case? Outer code 
> guarantees that
> duplicates won't be inserted anyway, so this constraint is implicit in 
> my case.

hashed_unique should be marginally better, but again you'd better 
profile that
assumption.

Thanks for using Boost.MultiIndex,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo