Wrong index name in 4.2 database upgrade routine

[kovshenin]

Seems like it's just an oversight in r31349, the signups table index is called domain_path, not domain.

[pento]

Huh, nice. We can commit this as soon as we're ready to start dev on 4.3, and backport it to the 4.2 branch.

[nacin]

We'll also need to drop the domain index, unless the query fails because we try to DROP an index that doesn't work. Do we need a new upgrade routine? What's the side effects of this bug?

[kovshenin]

No need to drop the domain index as it doesn't get created when the first part of the query fails. The side effect is that wp_signups doesn't get converted to utf8mb4 with a "Specified key was too long" error. From what I can see this doesn't affect updates on other tables.

[pento]

32099.2.diff​ adds an extra check on upgrade to fix any wp_signups tables with incorrect indexes.

[pento]

In 32378:

Upgrades: When converting to utf8mb4, we were trying to change the wrong index on wp_signups, causing the conversion to later fail.

Props kovshenin, pento.

See #32099.

[pento]

In 32379:

Fix an incorrect version number check in [32378].

See #32099.

[pento]

In 32380:

Upgrades: When converting to utf8mb4, we were trying to change the wrong index on wp_signups, causing the conversion to later fail.

Merge [32378] to the 4.2 branch.

Props kovshenin, pento.

Fixes #32099.