Robert Stojnic schreef:
Let me briefly repeat what I said earlier about my
experience with this
intersection thingy. Adding categories to lucene index is easy *IF* they
the article, e.g. try this:
This will give you category intersection of "Living People" and "English
in fraction of the second.
That's the dirty way. I've gone ahead and written an alternative way of
implementing category intersections using a fulltext search, which means
you can run the most crazy intersections; in fact, you can search in an
article's categories as if they were the page's contents. It's part of
the AdvancedSearch extension which I'm paid to write, but it'll be easy
to split off just the intersection functionality into another extension.
The upside is that I also have a special page front end ready to go.
I'll commit AdvancedSearch into SVN once I've worked out the bugs
(provided there are any; it's close to midnight now so I don't really
feel like testing stuff any more) and worked out stuff with my
'employer', which shouldn't take more than a few days.
On a technical level, the extension adds the categorysearch table (you
need to run update.php to actually create the table), which is basically
a rip-off from the searchindex table. It has a cs_page field referencing
page_id, and keeps itself updated using the LinksUpdate and
ArticleDeleteComplete hooks. There's also a maintenance script to
populate the table from scratch.
What I found that the hard part is keeping the index
updated. If we want
a fancy category
intersection system discussed here before we need to have an index that
is frequently updated,
that will be integrated with the job queue, that will understand
Understanding templates is no problem here, since the updater uses the
parser's notion of which categories the page is in, and the populate
script uses the categorylinks table.
Lucene is not that good with very frequent updates.
The usual setting is
to have an indexer,
make snapshots of the index at regular intervals and then rsync it onto
searchers. The whole
process takes time, although for a category-only index it will probably
be fast. I assume there
would be at least few tens of minutes lag anyhow. Our current lucene
easily be used for index distribution and such.
I really don't have the faintest idea how Lucene works or how MediaWiki
interfaces with it, but I do know that Lucene can handle the stuff we
put into the searchindex table. Since the categorysearch table is no
different, I think Lucene *should* be able to handle it pretty easily as
well. Could someone who actually has a clue about all this reply?
Roan Kattouw (Catrope)