EN.WP.ST47 wrote:

I assume you're referring to Special:PrefixIndex? It's working fine for me on latest SVN, I created a page called A_b and typing A_b works as does A b.

Assuming Dan is correct, this is fixed.

(In reply to comment #1)

I assume you're referring to Special:PrefixIndex?

I don't think so. This was reported on Wikipedia's Village Pump:
https://secure.wikimedia.org/wikipedia/en/w/index.php?title=Wikipedia:Village_pump_(technical)&oldid=442511080#Mediawiki_search_engine_confused_by_spaces_in_prefixes
motivated by this edit:
https://secure.wikimedia.org/wikipedia/en/w/index.php?diff=442060054&oldid=442059590

Compare
https://secure.wikimedia.org/wikipedia/en/w/index.php?title=Special%3ASearch&search=prefix%3AWikipedia_talk%3ANeutral_point_of_view%2FArchive
(There were no results matching the query.)
with
https://secure.wikimedia.org/wikipedia/en/w/index.php?title=Special%3ASearch&search=prefix%3AWikipedia+talk%3ANeutral+point+of+view%2FArchive
(45 results)

EN.WP.ST47 wrote:

I can find no documentation that even indicates that should work. Not that the documentation is good or anything like that, but just saying. Special:Prefixindex works just fine, and your test case illustrates exactly what that special page is for.

(In reply to comment #4)

Special:Prefixindex works just fine, and your test case illustrates exactly
what that special page is for.

Well, on Special:PrefixIndex you can't "search" in the page content ;-)
https://secure.wikimedia.org/wikipedia/en/w/index.php?title=Special%3ASearch&redirs=1&search=%22I+think+this+is+one%22+prefix%3AWikipedia+talk%3ANeutral+point+of+view%2FArchive&fulltext=Search&ns0=1

EN.WP.ST47 wrote:

I wonder if there's a "search sucks, we know" tracking bug.

• Bug 24775 has been marked as a duplicate of this bug. ***

This is fixed by Cirrus, I suppose it should be WONTFIX'ed?

I don't think so, I just typed in a certain string into a modified search page at [[Wikipedia:Help_desk/Header]] and this was the output:

https://en.wikipedia.org/w/index.php?title=Special%3ASearch&profile=default&search=Hello+all%2C+I+have+recently+been+enjoying+the+art+of+photography%2C+with+a+digital+camera+that+was+given+to+me+as+a+present.+prefix%3AWikipedia%3AHelp+desk%2FArchives&fulltext=Search

Actual expected output after removing "_desk/Archives" from the prefix:
https://en.wikipedia.org/w/index.php?title=Special%3ASearch&profile=default&search=Hello+all%2C+I+have+recently+been+enjoying+the+art+of+photography%2C+with+a+digital+camera+that+was+given+to+me+as+a+present.+prefix%3AWikipedia%3AHelp&fulltext=Search

Using the links in comment 9 above, I've verified this behaviour still exists in Cirrus. Whether you use underscores or spaces, the prefix search query doesn't work at all, and it will only work if you remove everything after the "prefix:Wikipedia:Help".

Reassigning to Cirrus's category.

Cirrus does the right thing with namespaces but not with titles actually.

Change 112633 had a related patch set uploaded by Manybubbles:
Handle _s as spaces in prefix:

https://gerrit.wikimedia.org/r/112633

and it only took two and a half years!

Change 112633 merged by jenkins-bot:
Handle _s as spaces in prefix:

https://gerrit.wikimedia.org/r/112633

Merged. Should go to production on the next deployment train. It'll hit wikipedias 2014-02-20.