[erlang-questions] [ANN] LETS - LevelDB-based Erlang Term Storage v0.5.3

Ciprian Dorin Craciun <>
Mon Nov 21 13:06:29 CET 2011


On Mon, Nov 21, 2011 at 13:59, Joseph Norton <> wrote:
>
> Ciprian -
>
> For encoding and then returning keys and values to the Erlang virtual machine, leveldb::Slice() is sufficient.  I didn't run any comparison tests but my assumption is that using std::string() requires (should require?) an extra memory allocation, copy, and deallocation for the std:string() object itself.
>
> Joe N.

    Thanks for the answer.

    I'll also contact the LevelDB developers to ask them about the
reason not export a version of get with the value as a slice. (I'll
let you know about their response.)

    Ciprian.


> On Nov 21, 2011, at 8:14 PM, Ciprian Dorin Craciun wrote:
>
>> On Mon, Nov 21, 2011 at 11:58, Joseph Norton <> wrote:
>>>
>>> Ciprian -
>>>
>>> Yes, your guess is correct.
>>>
>>> Joseph Norton
>>> 
>>
>>
>>    :D, but then the second question appears:
>>    * does this affect the performance in any way? (from what I've
>> seen in their code, they also use some kind of iterator to implement
>> `Get`;)
>>    * is there a reason not to use the `std::string`? (is it
>> inefficient from the C++ point of view, or it is when combined with
>> Erlang?)
>>
>>    I'm not in any way criticizing your work (actually when I've
>> studied the LevelDB code I also thought to use the iterator for
>> reads).
>>
>>    I just want to learn from your experience by not making the same
>> mistake twice. :)
>>
>>    Thanks,
>>    Ciprian.
>>
>>
>>> On Nov 21, 2011, at 3:09 PM, Ciprian Dorin Craciun wrote:
>>>
>>>>    I've thrown a quick look over your code
>>>> `https://github.com/norton/lets/blob/master/c_src/lets_nif.cc` -- as I
>>>> also want to make a LevelDB binding, but in Go, and I wanted to see
>>>> how you did it -- and I was curios about one thing: why you never use
>>>> `db->Get` but always for read operations you use
>>>> `db->NewIterator(...)`? (I guess it's because it doesn't return a
>>>> `Slice` but a `std::string`?)



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