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databaseerlangmnesia

Select random record from mnesia

I have an mnesia table t that contains records with a single field x. How can I select a random value x from t?

To avoid the entire of process of mathematical pedantry: I don't care about the details of the random number generation, I just want my result to generally not be the same every time.

Thanks,
-tjw

Solution

  • By using the mnesia:all_keys/1 (or dirty equivalent) function and the random module.

    random_value(Table) ->
    Keys = mnesia:dirty_all_keys(Table),
    Key = lists:nth(random:uniform(length(Keys)), Keys),
    [#record{x = X}] = mnesia:dirty_read({Table, Key}),
    X.

    Don't forget to initialize your seed using random:seed/3.