Update old job biggest id

[hladush]

Optimized query, my thought was that DB could find the job ID in mid table <10M of rows during secods, it's not true because it causes a whole table scan.
This update started to utilize the fact that a PK is indexed and it's a system_job_id bigint generated always as identity.
Now query is ~500 times faster
Tested with database

[Copilot]

Pull request overview

This PR optimizes the janitor’s “biggest old job ID” lookup to avoid an expensive scan/sort on updated_at by leveraging the indexed jobs.system_job_id primary key.

Changes:

• Change the old_job_biggest_id.sql query to order by system_job_id DESC (instead of updated_at DESC) to fetch the largest old job ID more efficiently.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

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[Copilot]

For consistency with other janitor SQL queries (e.g. stale_and_canceling_jobs_select.sql, old_jobs_delete.sql), this statement should end with a trailing semicolon. That also avoids accidental issues if the embedded SQL ever gets concatenated with additional statements.

Suggested change

	LIMIT 1
	LIMIT 1;