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lib/mariaex/cache.ex
defmodule Mariaex.Cache do
import :os, only: [timestamp: 0]
def new(size) do
{size, :ets.new(:cache, [])}
end
def lookup({_, cache}, statement) do
case :ets.lookup(cache, statement) do
[{_, _, info}] -> info
_ -> nil
end
end
def delete({_, cache}, statement, cleanup) do
case :ets.lookup(cache, statement) do
[{_, _, info}] ->
:ets.delete(cache, statement)
cleanup.(statement, info)
_ ->
nil
end
end
def insert({size, cache}, statement, data, cleanup) do
if :ets.info(cache, :size) > size, do: remove_oldest(cache, cleanup)
:ets.insert(cache, {statement, timestamp, data})
end
def update({_, cache}, statement, data) do
:ets.insert(cache, {statement, timestamp, data})
end
defp remove_oldest(cache, cleanup) do
{statement, _, data} = :ets.foldl(fn({statement, timestamp, data}, nil) ->
{statement, timestamp, data}
({_, timestamp, _} = actual, {_, acc_timestamp, _} = acc) ->
if timestamp < acc_timestamp do actual else acc end
end, nil, cache)
cleanup.(statement, data)
:ets.delete(cache, statement)
end
end