One some level, the real issue here is that different wikis are living on different slices (s1, s2, s3).

One possible solution is to replicate "shared" wikis (Wikidata and Commons) and possibly a few other "mother" wikis (at least En WP) into every slice. The uses cases that need to join enwiktionary with fawikibooks are rare or nonexistent; we don't need every wiki database to be accessible on every server. But we certainly want some of them to be universally accessible.

Can we do that?

On Wed, Nov 11, 2020 at 4:31 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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