[erlang-questions] Mnesia, disk_log and dets

wde <>
Wed Feb 17 18:13:34 CET 2010


thank you for your feedback. 


>Hi,
>
>Ulf knows probably everything about mnesia, I know it rather as a common user, but your ideas seems to be interesting. I would like to have database with mnesia API, but more efficient and more powerful backend... also more flexible and extend-able. I was playing with Mnesiaex but I've had some issues with dependencies and TC (Tokyo Cabinet) was chosen.
>  
>Anyway subject is interesting especially from the efficiency point of view. I'm looking forward to seeing your results :)
>
>--
>rgs,
>
>Dawid 
>
>Erlang Solutions Ltd, formerly Erlang Training & Consulting Ltd
>http://www.erlang-solutions.com
>
>
>----- Original Message -----
>From: "wde" <>
>To: "Ulf Wiger" <>
>Cc: "erlang-questions" <>
>Sent: Wednesday, February 17, 2010 7:38:11 AM GMT +00:00 GMT Britain, Ireland, Portugal
>Subject: Re: Re: [erlang-questions] Mnesia, disk_log and dets
>
>ok thank you.
>
>With Mnesiaex we can have our own storage backend for the  new "external_copies" type. 
>
>But instead of specifying a new copy type, I'm currently trying to understand how I can integrate a wrapper module
>like "mnesia_disc_backend" that handle all disc access (for disc_copies and disc_only_copies) , and do the same thing for the "ram_copy" type, by using a "mnesia_ram_backend" module.
>
>The idea is to offer more flexibility and easily change the backend for ram and disc I/O.
>
>
>Do you think I'm wasting my time or that there is no interest for something like that ?
>
>
>
>
>
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>
>
>>wde wrote:
>>> hello,
>>> 
>>> I'm reading the source code of Mnesia to understand how things work
>>> :+) If I have understood correctly, for "disc_copies" tables, data
>>> are written to disc by using the "disk_log" module. For
>>> "disc_only_copies" tables, Mnesia uses "dets".
>>> 
>>> What not use the same disk backend ?
>>
>>Originally, they did use the same back-end, but it turned out,
>>from experimentation, that dumping the entire table using disk_log
>>was /much/ faster than writing out the individual changes into
>>a dets file.
>>
>>BR,
>>Ulf W
>>-- 
>>Ulf Wiger
>>CTO, Erlang Solutions Ltd, formerly Erlang Training & Consulting Ltd
>>http://www.erlang-solutions.com
>>---------------------------------------------------
>>
>>---------------------------------------------------
>>
>>WE'VE CHANGED NAMES!
>>
>>Since January 1st 2010 Erlang Training and Consulting Ltd. has become ERLANG SOLUTIONS LTD.
>>
>>www.erlang-solutions.com
>>
>>
>
>
>
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