Should've been part of T143763: Remove unused bundling DB fields, but https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/Echo/+/306849/10/db_patches/patch-drop-user-hash-timestamp-index.sql wasn't included in the request. The index was left in the canonical SQL file for Echo too, until https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/Echo/+/563543/

What:

DROP INDEX /*i*/echo_notification_user_hash_timestamp ON /*_*/echo_notification;

Where: Everywhere that has the echo_notification table

When: At DBA's leisure (patch is merged, no code dependancy)

Is backwards compatible: Yes

Has been tested already: Index will have been dropped on wikis running master for a long time

Schema change progress:

Progress on x1

• eqiad T242749#5804469
• codfw