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DalmatinerDB query engine

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dqe src dqe_hist.erl
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src/dqe_hist.erl 

-module(dqe_hist).

-behaviour(dqe_fun).



-include_lib("mmath/include/mmath.hrl").



-export([spec/0, describe/1, init/1, chunk/1, resolution/2, run/2, help/0,

         compute/2, compute/3]).



-record(state, {

          time :: pos_integer(),

          count :: pos_integer(),

          htv :: pos_integer(),

          sf :: pos_integer(),

          acc = <<>> :: binary()

         }).



init([HTV, SF, Time]) when is_integer(Time) ->

    #state{time = Time, htv = HTV, sf = SF}.



chunk(#state{time = Time}) ->

    Time * ?RDATA_SIZE.



resolution(Resolution, State = #state{time = Time}) ->

    Res = dqe_time:apply_times(Time, Resolution),

    {Res, State#state{count = Res}}.



describe(#state{time = Time}) ->

    ["histogram(", integer_to_list(Time), "ms)"].



spec() ->

    {<<"histogram">>, [metric, integer, integer, time], none, histogram}.



run([Data], S = #state{htv = HTV, sf = SF, count = Count, acc = Acc}) ->

    Acc1 = <<Acc/binary, Data/binary>>,

    {Acc2, Hists} = execute(HTV, SF, Acc1, Count, []),

    {Hists, S#state{acc = Acc2}}.



help() ->

    <<"Converts measurement points of a timerange into a histogram. "

      "The arguments are a metric, the highest trackable value, "

      "and the significant figures (1..5).">>.



execute(HTV, SF, Acc, Count, AccEmit)

  when byte_size(Acc) >= Count * ?RDATA_SIZE ->

    MinSize = Count * ?RDATA_SIZE,

    <<Data:MinSize/binary, Acc1/binary>> = Acc,

    H = mk_hist(HTV, SF, Data),

    execute(HTV, SF, Acc1, Count, [H | AccEmit]);



execute(_HTV, _SF, Acc, _, AccEmit) ->

    {Acc, lists:reverse(AccEmit)}.



mk_hist(HVT, SF, Data) ->

    {ok, H} = hdr_histogram:open(HVT, SF),

    Values = mmath_bin:to_list(mmath_bin:derealize(Data)),

    [hdr_histogram:record(H, round(V)) || V <- Values],

    H.



compute(F, Data) ->

    mmath_bin:realize(mmath_bin:from_list([F(H) || H <- Data])).



compute(F, A, Data) ->

    mmath_bin:realize(mmath_bin:from_list([F(H, A) || H <- Data])).