MusikAnimal is right, however, Wikidata and Commons either have a sui generis slice, or they share it with a few very large wikis. Tools that do any kind of crosswiki analysis would instantly break, as most of them utilise joining by Wikidata items at the very least. 

I second Maarten here. This would mean a lot of things that currently require a (relatively simple) SQL query would need a full script, which would do the join at the application level. 

I fully understand the reasoning, but there needs to be some replacement. Intentionally introduce breaking changes while providing no "new standard" is a bad pattern in a community environment. 


On Wed, Nov 11, 2020, 10:31 PM MusikAnimal <> wrote:
Technically, cross-wiki joins aren't completely disallowed, you just have to make sure each of the db names are on the same slice/section, right?

~ MA

On Wed, Nov 11, 2020 at 4:11 PM Maarten Dammers <> wrote:

Hi Joaquin,

On 10-11-2020 21:26, Joaquin Oltra Hernandez wrote:
TLDR: Wiki Replicas' architecture is being redesigned for stability and performance. Cross database JOINs will not be available and a host connection will only allow querying its associated DB. See [1] for more details.

If you only think of Wikipedia, not a lot will break probably, but if you take into account Commons and Wikidata a lot will break. A quick grep in my folder with Commons queries returns 123 lines with cross database joins. So yes, stuff will break and tools will be abandoned. This follows the practice that seems to have become standard for the WMF these days: Decisions are made with a small group within the WMF without any community involved. Only after the decision has been made, it's announced.

Unhappy and disappointed,


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