fix: add pessimistic lock when fetching next qs batch and marking failed

[m90]

Ticket https://phabricator.wikimedia.org/T354797

[deer-wmde]

Generally this looks great to me, I'm just still lacking a bit database knowledge and am curious where the unlocking does happen again, is it something Laravel takes care of in its connection teardown or something or is it even the DB itself that does it? Just asking out of interest and trying to see if there's footgun potential (but I don't think so actually)

[m90]

Generally this looks great to me, I'm just still lacking a bit database knowledge and am curious where the unlocking does happen again, is it something Laravel takes care of in its connection teardown or something or is it even the DB itself that does it? Just asking out of interest and trying to see if there's footgun potential (but I don't think so actually)

From what I understand the END TRANSACTION statement will unlock everything that was locked within the transaction.