Message-ID: <418070AF.1070503@johnmeinel.com>
Date: Wed, 27 Oct 2004 23:08:15 -0500
From: John Meinel <tla@johnmeinel.com>
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To: James Blackwell <jblack@merconline.com>
Subject: Re: [Gnu-arch-users] Re: Potential flaw in patch-log pruning
	in	proposal
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James Blackwell wrote:
> John Meinel wrote:
> 
> 
>>I think the idea that the patch name gets kept, but you can optionally 
>>keep the patch-log itself is a good idea. So the '{arch}/=merged' file 
>>would contain the equivalent of
>>tla logs --merges
> 
> 
> There's a catch to doing this. I've meant to (and put off for) quite a
> bit to build a command that lets you easily see in which revisions a
> "file" was changed. 
> 

Doesn't fai have this with fai revisions --modified filename?

Basically you just go back and parse the patch logs, right.

> 
>>Or possibly with the summaries as well. (This isn't as important, and 
>>might cause file size to go up again.)
>>
>>Then when tla wants to check if a patch has already been merged, it can 
>>look for the patch-log, and secondly look for the entry in =merged.
> 
> 
> Aye. I think this would be "good enough" for replay --skip-present. 
> 

Sure, and I think that's what we would be stuck with. But remember, you 
still have the patch log on the main branch (whatever the name of the 
merge is). So you can still say when the official tree was modified. And 
if you keep something like
tla logs --merges

Then you can also see what other revisions contributed to it. You don't 
know exactly which did what, but you do keep context sensitive, and you 
can locate it relative to just a couple packages.

> 
>>It might be nicer if =merged was some sort of indexed file format, so 
>>that lookups could be faster, but greping even a 120K file doesn't seem 
>>very expensive.
> 
> 
> Though I'm in favor of this, actually it can get to be quite a bit more
> expensive than this. Though it wouldn't be this bad for small/medium
> sized projects, larger heavily developed projects will see a
> concatenated patch-log on the order of 5-6 megabytes per working
> copy/revision in the library.
> 

I don't think =merged is going to be all the patch logs "cat"ed 
together. It's supposed to be just the fully qualified revision name.

I believe that's what Matthieu stated. The sum of all the patch logs was 
 > 7 MB for all of the logs, but for just the list of revisions it is 
only 120Kb.

I was assuming xtla is at least medium sized. Perhaps you are thinking 
more along the lines of a "gcc". I'm not really sure how to scale that big.

One other possibility is to use ".zip" files instead of tarballs. zlib 
has native support for them as of something like 1.1 or 1.2. Basically 
they store each file compressed individually, with an index to find each 
one. You get better compression with a tarball because you can compress 
larger chunks, but you don't get indexing.

.zip has traditionally been a windows thing, but since zlib supports it 
(and python started using it as an alternative to storing your scripts 
in individual files). I see it as becoming useful in more places.

7zip is an interesting compromise. You have an index, but only to the 
chunk level, where each chunk could be more than one file.

But really, for something like patch logs, all you need is one indexed 
file that lets you quickly find if one exists, and then you can pack the 
actual text of the log however you want.
John
=:->

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