On Fri, Jul 31, 2015 at 2:21 PM, Alvaro Herrera <alvhe...@2ndquadrant.com> wrote: > I think the only way to produce usable estimates is to report more than > one number. And in the particular case of lazy vacuuming, ISTM the way > to do it is to consider heap scanning as one phase, index cleanup as > another phase; these two phases can be interleaved. And there's a final > heap scan which is a third phase, which can only run after phases one > and two are complete.
That's not really right. There's a phase three for each phase two. Put in terms of the code, what we're calling phase one is lazy_scan_heap(), which prunes all pages, sets hint bits, collects dead TIDs, and maybe marks the page all-visible. When lazy_scan_heap() fills up maintenance_work_mem, or when it reaches the end of the heap, it does phase two, which is lazy_vacuum_index(), and phase three, which is lazy_vacuum_heap(). Phase one - lazy_scan_heap() - then keeps going from where it left off. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
