Mnesia query: less or equal than given key

Sean Hinde sean.hinde@REDACTED
Mon Sep 19 16:52:05 CEST 2005


You could try first looking up the exact key, and if not found then  
do a mnesia:dirty_prev/2 to get the next smallest. You would need to  
be careful of transaction safety..


On 19 Sep 2005, at 15:06, Erik Reitsma (RY/ETM) wrote:

> Hi all,
> Using mnesia, is there an efficient way to find the smallest entry  
> in a table with a key equal to or less than a given key?
> So suppose that I have keys 10, 23, 33, 34, 56, 100 and I look for  
> 26, I want to get 23 back. If I look for 23, I should get 23.
> I could select all entries smaller than or equal to my key, and  
> then take the largest of those, but it seems like I would get an  
> intermediate list that may consist of the entire table (i.e. if my  
> key is larger than the largest key in the table).
> I could make my own binary search (the keys are integers anyway),  
> but I wondered if there would be a more elegant way.
> Regards,
> *Erik.

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