Remove feature flag for use_cte_for_group_issues_search
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21521 fixes a bug, but the bug was introduced by an optimisation. The optimisation looks like it's no longer necessary, from our experimentation, but it's hard to be certain as the query is quite complicated and performs differently on the primary compared to the secondaries.
The feature flag is enabled by default, so when it's off, we're using the new code. Once we've set it to zero, and we're happy that things work, we should:
- Remove references to the flag.
- Revert https://gitlab.com/gitlab-org/gitlab-ce/commit/c03386c3914feca56802e6f99bbd0fd08d269472.
- Remove it from the spec (there's a comment with a link to this issue).
Edited by Sean McGivern