My first question is what does ETS add on top of just storing state in a GenServer? In the documentation I see it is used as a “cache”, does this mean it won’t always return the latest data? There’s a warning in the Elixir guide about using it prematurely: Warning! Don’t use ETS as a cache prema…

No expert here – but from the reading I’ve done 90% of the time you’re better off just storing state in the GenServer. There is a couple of interesting use cases since ETS tables have some access control: public — Read/Write available to all processes. protected — Read available to all processes…

Addressing your points directly, what does ETS add on top of just storing state in a GenServer? ETS is usually used as a way to share state between processes/GenServers. does this mean it won’t always return the latest data? No. ETS is a key-value store, it will be updated just as current as…

Using ETS as a cache is only one of its many uses. A major use is for storing LARGE amounts of data in memory. This is a typical use, for example it is how mnesia stores data in memory. So if your gen_server stores large amounts of data then maybe using ETS is a better alternative. As has already b…

You can use ETS in many places where you use your database depending on your use cases. One easy win is putting all your lookup data into ETS tables. ETS is very fast when you do key lookups. I do a little bit of ETL and use ETS tables extensively to store lookup data, to write out to ets tables as …

[image] minhajuddin: I use :ets.tab2file(‘./data/myetsdb.ets’) as soon as I start the app and do a :ets.file2tab(:mydb, ‘./data/myetsdb.ets’) before I shut down or run into an error. Hi, please check the order of this … should it not be the other way round?

[image] elie: My first question is what does ETS add on top of just storing state in a GenServer? You could simulate the complete interface of the :ets module with GenServer. However, such implementation would be very inefficient in some cases. A typical example is in memory k-v. If you do t…

Please correct me if I’m wrong, but it turns out that eg. info about Elixir modules is stored in ETS according to the source code .

You are right (I am not sure what info about the modules is stored). There is a lot of information stored in ets tables. Simply opening iex will create ~19 ets tables. iex(1)> :ets.all [Logger.Config, IEx.Config, :elixir_modules, :elixir_config, :file_io_servers, :inet_hosts_file_byaddr, :inet_hos…

I choose ETS whenever I need to keep data despite of a GenServer process state. When a GenServer termination would imply relevant data loss. Specially due to the let it crash approach :wink:

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Why use ETS? When not to use it?

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minhajuddin March 28, 2017, 9:16am 7

Yeah . Fixed it