Release v2.0.0 - The "Database-Driven Development" Release! · Betterment/delayed

Numerous changes focused on index coverage and query performance went into this release. At a high level, this release consists of: New optional-but-encouraged DB indexes (available via rake delayed:install:migrations) that improve index coverage of all queries. Adjustments to queries to improve selectivity and reduce cost (# of scanned/filtered rows). First class support for HOT updates in PostgreSQL (during job pickup query). Daylight savings time fixes in non-UTC time (:local) contexts. (#81) Job timeouts can no longer be rescued from within the perform method as a StandardError (#66) YMMV (and will depend heavily on the contents of your queue and the number of workers you run). In real-world at-scale testing against a PostgreSQL (RDS Aurora) backed queue, in an environment where the table had many millions of future-scheduled and/or failed rows (i.e. "non-claimable" rows), improvements were observed across the board: The worker pickup query saw a 100-1000x query time improvement. The "monitor" queries saw on net a 10-100x improvement. Overall CPU usage and disk I/O of an active (but not back-logged) PostgreSQL queue dropped significantly.