Faster loading of large files

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created 2002 · complexity intermediate · author Erik Remmelzwaal · version 6.0

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A user can sometimes experience long load times on very large files. While the definition of a very large file depends on the user, their machine specifications, and their patience, at one point or another any user can experience a load time delay. A method to load these files faster is to remove some of the options available like undo histories, syntax parsing, and swap file creation.

By adding the following to the .vimrc file, the user can automatically remove certain options for files over a certain size (in this example, 10mb).

:let g:LargeFile=10
:e

" Protect large files from sourcing and other overhead.
" Files become read only
if !exists("my_auto_commands_loaded")
  let my_auto_commands_loaded = 1
  " Large files are > 10M
  " Set options:
  " eventignore+=FileType (no syntax highlighting etc
  " assumes FileType always on)
  " noswapfile (save copy of file)
  " bufhidden=unload (save memory when other file is viewed)
  " buftype=nowritefile (is read-only)
  " undolevels=-1 (no undo possible)
  let g:LargeFile = 1024 * 1024 * 10
  augroup LargeFile
    autocmd BufReadPre * let f=expand("<afile>") | if getfsize(f) > g:LargeFile | set eventignore+=FileType | setlocal noswapfile bufhidden=unload buftype=nowrite undolevels=-1 | else | set eventignore-=FileType | endif
    augroup END
  endif

See also

• Edit large files quickly plugin to handle many of the above changes and more

Comments

I changed the code a bit here and the final result is the following. Differences are:

• Files with filesize too large are recognized too (getfsize = -2)
• Readability
• Message that options are changed at startup
• Got rid of things like my_autocommands_loaded (I didn't get the use...)

" file is large from 10mb
let g:LargeFile = 1024 * 1024 * 10
augroup LargeFile 
 autocmd BufReadPre * let f=getfsize(expand("<afile>")) | if f > g:LargeFile || f == -2 | call LargeFile() | endif
augroup END

function LargeFile()
 " no syntax highlighting etc
 set eventignore+=FileType
 " save memory when other file is viewed
 setlocal bufhidden=unload
 " is read-only (write with :w new_filename)
 setlocal buftype=nowrite
 " no undo possible
 setlocal undolevels=-1
 " display message
 autocmd VimEnter *  echo "The file is larger than " . (g:LargeFile / 1024 / 1024) . " MB, so some options are changed (see .vimrc for details)."
endfunction