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https://issues.apache.org/jira/browse/ARROW-5502?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16861100#comment-16861100
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Neal Richardson commented on ARROW-5502:
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Memory mapping would make the loading in memory to copy to R lazy, and will be 
necessary for things like {{read_parquet(f, col_select)}} to not read all 
columns into Arrow before copying to R.

Yes, I believed it was possible now, but that's not a friendly enough interface 
for package users, IMO. 

> [R] file readers should mmap
> ----------------------------
>
>                 Key: ARROW-5502
>                 URL: https://issues.apache.org/jira/browse/ARROW-5502
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: R
>            Reporter: Neal Richardson
>            Priority: Major
>             Fix For: 0.14.0
>
>
> Arrow is supposed to let you work with datasets bigger than memory. Memory 
> mapping is a big part of that. It should be the default way that files are 
> read in the `read_*` functions. To disable memory mapping, we could use a 
> global `option()`, or a function argument, but that might clutter the 
> interface. Or we could not give a choice and only fall back to not memory 
> mapping if the platform/file system doesn't support it.



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