Mnesia not suitable for time series storage?

Ulf Wiger <>
Wed Jul 13 15:47:49 CEST 2005


Den 2005-07-13 15:10:39 skrev Serge Aleynikov <>:

> I believe the main problem with the speed is that you organized the tick  
> table to be a bag and also have another BTree index on the date.  The  
> search time related to inserting into this table will grow  
> logarithmically.

For the record, mnesia indexes are bags, not BTrees.

I think the problem is that mnesia's bag tables store
only one copy of each object -- i.e. it doesn't allow
duplicate objects (even though duplicate keys are OK).

In ets, there is 'duplicate_bag', which doesn't check
for duplicates, but mnesia will basically have to do
a linear search through all objects with the same key.

I can imagine that duplicate_bag would mess up the
mnesia transaction support pretty badly.

/Uffe




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