On Mon, 25 Jul 2011, Marc Deop wrote:
> It's more than twice as fast than the previous sh script.
In part this is /bin/sh v /bin/bash and using 'bashisms'
matter, but yes, I did not seek to optimize a teaching
throwaway
> 1- m5sum the file we need
... actually the NAME of the file, to make it explicit we are
not looking at content [also a reasonable approach if one is
looking to find and de-duplicate a filestore]
> 2- look for the first letter of the hash
... actually this may be more than a single letter of the
hash --- with ca 3000 files, and 16 hash characters,
we should end up with about 200 files per
subdirectory. The filesystem should be doing some sort of
index as well -- as I recall, a B-tree in the case of
extN but I've not expressly looked. The php case was
mentioned, however, and its directory searching is less
optimal
We have a customer with a similar problem with a naiively
written set of home brewed PHP code, and are helping them work
through similar issues
> 3- get into the directory
> 4- now we look for our file
... this is probably a single operation to suck the sub-directory
listing into an array in php, and use an associative
match
but you are right, we are moving increasingly away from a
CentOS issue to a more general coding style issue
-- Russ herrold
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