(If your third-party tool does not read data from [wbc_entity_usage] via Wiki Replicas, please ignore this email)

Hello everyone,

planning is underway to move the Wikibase [wbc_entity_usage] tables for all wikis to a different “x1 extension cluster” to improve database space usage [0]. We expect that few, (if any) third-party tools directly rely on this table — but before making any breaking changes, we want to confirm that.

If your tool uses this table, hearing from you will help us understand how many tools are affected and what that usage looks like, so we can plan the migration accordingly.

[wbc_entity_usage] tracks which Wikidata entities are used on a given Wiki’s pages, and also powers Wikidata-triggered Recent Changes and Watchlist injections to client Wikis.

// What's affected //

If you operate a tool that reads from the [wbc_entity_usage] table — through Wiki Replicas or directly from SQL, this may affect you.
This is especially likely if your query JOINs [wbc_entity_usage] with other MediaWiki tables (e.g. ‘page’, ‘revision’), since cross-cluster JOINs will stop working when the migration is completed.

// What to do //

Please comment on [1] (even a simple “yes, I am affected” is helpful). If you can share more, we'd like to know:

• The Tool name and location (e.g. Toolforge, repo link).

• If your query JOIN’s [wbc_entity_usage] with other tables, please tell us which.

• How often the queries run against [wbc_entity_usage], (e.g. real-time, daily, weekly, manually).
  
  

Please be aware:

• [wbc_entity_usage] will eventually be removed from Wiki Replicas and direct SQL. Existing queries against this table will need to be replaced with a different approach. 

• During the lengthy transition period, the tables will still operate, so existing queries will continue to function until access is turned off when the migration is complete [2].

• Once the Wiki Replicas access ends, tool users should switch over to using the MediaWiki API [3] or Recent Changes API [4] to read changes instead.
  
  Queries on the table will no longer work *after* the migration is completed, so they will need to be adjusted.

// Links //

[0] - https://phabricator.wikimedia.org/T424133
[2] - https://phabricator.wikimedia.org/T424440
[3] - https://en.wikipedia.org/w/api.php?action=help&modules=query%2Bwbentityusage

[4] - https://www.mediawiki.org/wiki/API:RecentChanges

Please report if your tool is affected to the relevant Phabricator ticket:
[1] - https://phabricator.wikimedia.org/T430289

Thank you,
Danny (on behalf of the Wikidata For Wikimedia Projects team)