Cloud manual migrations

Sourcegraph.com occassionally requires migrations be ran against it that are not ran against other deployments of Sourcegraph.

Examples of this include:

We soon want to eliminate the need for such manual migrations against prod (tracking issue), but in the meantime this document serves as a list of manual migrations that have been ran against production.

Aug 3rd, 2020 - read only user addition

https://github.com/sourcegraph/sourcegraph/pull/12561

Exact SQL:

TODO(efritz,chayim)

Impact if this migration is undone: Sourcegraph personnel would need to use the write-only sg user, does not impact product or performance behavior.

July 27th, 2020 - index addition

https://gist.github.com/rvantonder/7745c2360cfced6f12c922588bfbef79

https://twitter.com/beyang/status/1287826896281989120

https://github.com/sourcegraph/sourcegraph/pull/12591

Exact SQL:

CREATE INDEX CONCURRENTLY repo_name_idx ON public.repo USING btree (lower(name::text) COLLATE pg_catalog."C");

Impact if this migration is undone: Degraded performance when searching a lot of repos with a common prefix, no impact otherwise.