Re: Ignore contents: compare by file name, date/time & size only

[Kai <kai willadsen gmail com>]

On 12 December 2010 15:13, Martin Spacek <gmane martinspacek mm st> wrote:
> I often need to compare directories with 10s or 100s of GB of binary files
> in them (generally between my internal and external drives). Coming from
> "Beyond Compare", I'm used to directory comparisons relying only on file
> name, date/time, and file size to decide which files differ, which are
> missing, etc.

I can understand why you'd want this in cases like yours, but...
that's kinda dodgy, and not something we'd do without warning.

Off the top of my head, I think that if we were to force any such
'fast' comparison, we would probably key off file type (i.e., binary
files) and file size (i.e., full comparison on any files under 500K,
dodgy comparison on anything larger) and there would *have* to be some
indication that the files were not actually compared.

> Meld looks great, but seems to insist on comparing the contents of each
> file. This is far too expensive an operation for big files. Am I missing
> some hidden option that allows you to turn off "compare by contents" in the
> directory comparison view? Would this be a difficult feature to add?

No, and maybe, in that order. The directory comparison code is a bit
hairy in places, and the difficulty would depend on exactly how it was
to be implemented.

> I can't seem to find any mention of this in the mailing list. I did a brief
> search of bugzilla and came up with nothing. I'm running the latest version
> from git. All I found were some blogs/articles mentioning this limitation in
> Meld.

Well, feel free to file a bug. There are several 'directory comparison
could be faster' bugs already, but more specific requests are always
welcome. There's also a fair bit of low-hanging fruit in optimising
Meld's directory comparison.

(I wrote this response a couple of days ago, and in the interim I've
mostly rewritten DirDiff._files_same() to be faster in a few
situations, but it's not pushed anywhere. If anyone wants to work on
this stuff, I can put the rework up.)

cheers,
Kai