Thanks for the replies @smon and @josevalim! 
sentient-wendy
johnwangwjq
Just out of curiosity, if there are huge static files in the priv folder, will this way make the compiled binary huge? as well as the module loading time…
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NobbZ
It will only affect release size. The Priv folder is only included there, not in individual modules.
Also it won’t increase module load time as it’s not included in modules as I said.
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johnwangwjq
Thank you @NobbZ. Please pardon me(a newbie) for digging a bit more:
- Where are the artifects stored after being loaded as a module attribute at compile time?
- using the example Jose mentioned above
@bar_contents File.read! "priv/foo/bar", ifpriv/foo/baris a huge vidoe file, what is the@bar_contentsafter the program being compiled(in the BEAM)? Is it something a pointer to the bar file or a thing holding all the data of that file.
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NobbZ
Copying files into an attribute indeed increases module size. Though that is not related to the Priv folder.
Due to how module attributes in elixir work, you can assume that each usage of the attribute causes a literal copy of the file.
For some data types there might be optimisations but assume there are not.
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johnwangwjq
Thanks a lot @NobbZ . Sorry for my question is not related to this topic. Anyway, just to confirm what I’ve understood so far:
By “copying files into an attribute”, are you saying @bar_contents File.read! "priv/foo/bar" is actually copying the bar into attribute bar_contents? (hence it increase the module size)
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NobbZ
Your question is indeed related, though I misunderstood your first phrasing of the question, as you asked solely about the Priv folder not about attributes. I should have scrolled back to the post you have quoted, then I might have seen it in the context…
Yes. File.read! returns the file content as a binary, so the attribute will contain the binary representing the files content. Though it won’t be saved as part of the module until the attribute is actually used in a way that would “generate appropriate code” or persisted into the module by using Module.register_attribute (I might misremember the function name).
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johnwangwjq
Thank you very much @NobbZ. I’m clear now. I’ve compiled a simple code reading a big file into an attribute. The compiled beam file is big, so the loaded binary is indeed stored in the beam file( whereelse could it be anyway 
I actually love this way to handle runtime resourcse that have to be deliveried along with the release. It make the release structure simple and neat. No matter they’re in the /priv folder or in beam files, you need pack them into somewhere in your release anyway.
Thanks again.
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