New trading systems platform

Ulf Wiger (AL/EAB) <>
Fri Jul 8 10:25:44 CEST 2005


HP Wei wrote:
>   I do not use Erlang often enough to make comments on
>   data storage using Mnesia.
>   I just want to point out that to store tick data
>   of many years needs a LOT of disk space plus
>   the capability of compression (when writing)
>   (and decompression when reading)  in your database design.

Some form of archiving mechanism seems to be needed.
Re. compression, there is of course a very convenient
form available to erlang programmers:

   Bin = term_to_binary(Data, [compressed]).

Decompression is transparently done by binary_to_term(Bin).

This uses LZW compression on the binary. Perhaps this is
not good enough? 

Perhaps one could come up with a caching scheme in Mnesia,
where table segments can be converted from ram_copies
to disc_only_copies after a certain time? One can use a 
custom fragmentation scheme that divides objects into time
periods. How many fragments could one have in one table?

/Uffe



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