There are often cases where I (and other people) want to make queries which involve finding items which have (or don't have) a label (or description or alias) in a particular language. In my experience, these queries are often slow or time out. It would be useful to either improve the speed of the existing queries somehow, or provide another way to filter by language which is faster.

For example, this recent request wanted all disambiguation items with an English description which have a description other than the usual description for such items. There I posted this query which works for English. I was also able to adapt it to produce this query for German. I then wanted to query for Austrian German, but the following just times out:

select * {
  hint:Query hint:optimizer "None" .
  ?item wdt:P31 wd:Q4167410 .
  minus { ?item schema:description "Wikimedia-Begriffsklärungsseite"@de-at }
  ?item schema:description ?desc filter (lang(?desc) = "de-at") .
}

I've tried various things and the one thing that stands out to me is that queries for simple triples are fast even when huge amounts of data are involved, e.g. select * { ?item schema:description "Wikimedia-Begriffsklärungsseite"@de-at } gives over 800 thousand results in just over 5 seconds and select * { ?item wdt:P31 wd:Q4167410 } gives over 1 million results in under 9 seconds. That suggests to me that one option would be to add something like ?item someprefix:hasLabelInLanguage "de-at".

More examples of when I've wanted something like this:

A few days ago I wanted to select all humans with Japanese labels, and then filter for labels which looked like they needed fixing (e.g. those which included disambiguation information). I ended up having to download and parse a data dump because I couldn't find a way to make a query that didn't time out.

A while back, I wanted to find all labels for a small language (only a few thousand labels) so that I could check and fix the capitalisation (many items should be lowercase, but are currently capitalised since they get copied from the automatically capitalised MediaWiki page names). I ended up having to use one of Magnus's tools to fetch the labels because the queries I tried timed out.