Nice work on the program! To answer your questions:

• Does this help you, given the caveats? Would you start using, e.g., weekly deltas if I posted them?

It is helpful in that it is ready for use now, and is very easy to use. I would probably need some time to automate it for my application, but it is possible that I could consume weekly deltas within a week or two. I'm not sure if it'd be worth your while. See more below.

• If you actually ran the dltp command above, did you have any trouble? How long did it take?

I gave it a run with the two latest pages-article dumps from simplewiki (http://dumps.wikimedia.org/simplewiki/) and it worked well with pack [1] and unpack [2]. Simplewiki is about 89 MB and dltp took about 10 seconds to generate a file of 4.2 MB (the dump files were already unzipped) . Unpacking took about 12 seconds to generate the 450 MB xml file. For reference, this is a Windows 7 machine with a dual-core 2.2 GhZ processor and 2 GB memory. Zipped took longer: about 2 minutes. I'll try the English Wikipedia counterparts tomorrow, but I'd guess it wouldn't take more than 25 min for unzipped.

I also tried cut / merge, but didn't really have anything meaningful to use, so can only testify that they didn't fail.

[1] dltp386.exe simplewiki-20130813-pages-articles.xml simplewiki-20130724-pages-articles.xml [2] dltp386.exe simplewiki-20130813-pages-articles.xml.dltp.gz

• If you'd use this, what sort of project are you thinking of on what sort of machine?

I'd use it for XOWA: https://sourceforge.net/projects/xowa/. This is a desktop app that runs on an individual user's machine for reading Wikipedia offline. I've had a few users ask about not having to download the entire dump every time, so you may see some delta usage there. Unfortunately, the user base is currently small (700 total downloads per month = ??? unique users), so it would not be worth your time to post the deltas solely for my benefit.

• Which wiki (enwiki, etc.) would you want diffs for?

Certainly, the 3 largest ones: enwiki, dewiki, frwiki. If possible, the 8 wikis with more than 1 million articles. XOWA can read any wiki, but it wouldn't make sense to post diffs for a small Wikipedia (Latin) when there would be no one to download them.

Also, this is probably outside the scope of dltp, but is there any way for the diff file to be self-contained? For example, if the old dump had 10 articles and the new dump had 11 articles with 1 new article and 1 changed article, then the diff file would only have 2 articles: the 1 new article and the 1 changed one. This may not save as much space, but it'd be easier for users to work with the delta file, then to remember to keep the original dump file around.

Hope my feedback is useful. Good luck.

On Tue, Aug 13, 2013 at 6:48 PM, Randall Farmer randall@wawd.com wrote:

[Adding wikitech once more with feeling. Sorry for all of the copies, Xmldatadumps-l.]

Hi, everyone.

I've been working on a tool to generate smaller update files from XML dumps by just saving the diff between the previous dump and the latest revision. It doesn't aim to do everything the new dump format does, and indeed it looks like the dumps project will make it obsolete at some point, but I'm putting this out there to see if it's useful in the interim.

You can get it at https://github.com/twotwotwo/dltp

After downloading one of the binaries, you can put it in a directory with enwiki-20130805-pages-articles.xml.bz2 and run:

./dltp http://www.rfarmer.net/dltp/en/enwiki-20130805-20130812-cut-merged.xml.dltp....

That download is ~50 MB, but it expands to about 4GB of XML, consisting of the latest revision's text for every page that was updated 8/5-8/12. (A diff for 7/9-8/5 was 440MB.) You can pipe the XML output to something, rather than saving it to a file, using the -c flag.

This all sounds great, and maybe it is if bandwidth is your bottleneck. There are lots of important caveats, though:

• *It looks likely to be obsoleted by official WMF diff dumps. *I started

on this a while back, and at the time, from what I'd read, I thought diff dumps weren't a high priority for the official project so might be worth implementing unofficially [ed: looking back, I probably should've been more cautious about this]. More recently it sounds more like official diff dumps actually might not be all that far off, so if you invest in using this, it might not pay off for all that long.

• These diffs give you *only the latest revision* of each page in namespace

0. No full history.

• You have to keep the old dump file around.
• The tool reads and *unzips* the old dump each time. bunzip2 is slow, so *you

may want to keep reference XML in uncompressed form*, or (better) compressed with gzip or lzop.

• On Windows, dltp unzips at slower than native speed, so there's even more

reason to store your source file uncompressed.

• No matter what, the old file can take a while to read through; *5-25

minutes to expand the file, depending on how your reference XML is stored, is entirely plausible.*

• It uses adds-changes dumps, so it doesn't do anything to account for

deletions or oversighting.

• *It's new, non-battle-tested software, so caveat emptor.*

So, I'm curious:

• Does this help you, given the caveats? Would you start using, e.g.,

weekly deltas if I posted them?

• If you actually ran the dltp command above, did you have any trouble? How

long did it take?

• If you'd use this, what sort of project are you thinking of on what sort

of machine? (A public site hosting Wiki content or something else? Big server, VPS, desktop? Linux or another OS?)

• Which wiki (enwiki, etc.) would you want diffs for?

Other than that the source is out there and anyone can use it, I'm not promising to post deltas or anything now (since perhaps many folks would rather wait on official delta dumps, etc.). But interested to see if there's any potential use here.

Best, Randall _______________________________________________ Wikitech-l mailing list Wikitech-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikitech-l