https://www.wikidata.org/w/index.php?title=Wikidata:Requests_for_deletions&oldid=5047750#Q2461754

https://www.wikidata.org/wiki/Q304597 and https://www.wikidata.org/wiki/Q2461754

One known way to end up with two or more items are to create the item partly in two or more different languages, where the languages in each creation does not overlap. This is often done when people tests in their own language. It is not possible to check for this situation, it is only possible to check for a failing save due to this condition when multiple languages are involved.

This check (it was inside a transaction) is relaxed to avoid blocking access to the database for write operations for prolonged time. There is a soft constraint that replaces this, but that constraint can (and will) fail due to race conditions.

As the number of items grows, and the items are used on Wikipedia, the duplicates will be identified and removed.

I'm not sure, but some duplicates could be identified by comparing similar links in different Wikipedia-projects. It could also be possible to make a double check against the existing iw-links on the Wikipedia sites and see if those match up with the sitelinks on Wikidata.

reza: Dup of bug 44763?

Reedy: no.

There's no real way to prevent this. I'll close this as wontfix. Sorry.