The plan is to do this differently than the usual schema changes, first apply it to production and make sure it's working fine in a couple of wikis. And then make the patch in core to drop the column. We need to also wait for T299424 to finish before being able to make the patch in core.
This is already done in beta cluster.
Wikis being cleaned:
[x] testwiki
[x] itwikisource
And then section by section:
[x] s5: Done
[x] s2: Done
[x] s8: Done
[x] s4: Done
[x] s6: Done
[] s7: Done except on eqiad master
[] s3: Done except on eqiad master
[] s1: Done except on codfw and eqiad masters
Query:
```lang=sql
ALTER TABLE templatelinks
DROP COLUMN tl_namespace,
DROP COLUMN tl_title;
DROP INDEX tl_backlinks_namespace ON templatelinks;
DROP INDEX tl_namespace on templatelinks;
OPTIMIZE TABLE templatelinks;
```