[erlang-questions] Mnesia, disk_log and dets

wde <>
Wed Feb 17 08:38:11 CET 2010


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 ?












>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
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