Обсуждение: freeze cannot be finished
Hello! Could anyone review patch suggested by Jeff Janes ? Initial thread http://www.postgresql.org/message-id/flat/1384356585.995240612@f50.i.mail.ru#1384356585.995240612@f50.i.mail.ru Thanks in advance! > > On Wed, Nov 13, 2013 at 3:53 PM, Sergey Burladyan < eshkinkot@gmail.com > wrote: > >Jeff Janes < jeff.janes@gmail.com > writes: > > > >If I not mistaken, looks like lazy_scan_heap() called from lazy_vacuum_rel() > >(see [1]) skip pages, even if it run with scan_all == true, lazy_scan_heap() > >does not increment scanned_pages if lazy_check_needs_freeze() return false, so > >if this occurred at wraparound vacuum it cannot update pg_class, because > >pg_class updated via this code: > > > > new_frozen_xid = FreezeLimit; > > if (vacrelstats->scanned_pages < vacrelstats->rel_pages) > > new_frozen_xid = InvalidTransactionId; > > > > vac_update_relstats(onerel, > > new_rel_pages, > > new_rel_tuples, > > new_rel_allvisible, > > vacrelstats->hasindex, > > new_frozen_xid); > > > >so i think in our prevent wraparound vacuum vacrelstats->scanned_pages always > >less than vacrelstats->rel_pages and pg_class relfrozenxid never updated. > > Yeah, I think that that is a bug. If the clean-up lock is unavailable but the page is inspected without it and found notto need freezing, then the page needs to be counted as scanned, but is not so counted. > > commit bbb6e559c4ea0fb4c346beda76736451dc24eb4e > Date: Mon Nov 7 21:39:40 2011 -0500 > > But this was introduced in 9.2.0, so unless the OP didn't upgrade to 9.2 until recently, I don't know why it just startedhappening. > > It looks like a simple fix (to HEAD attached), but I don't know how to test it. > > Also, it seem like it might be worth issuing a warning if scan_all is true but all was not scanned. > > Cheers, > > Jeff > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general > --
Вложения
Committed, thanks for the report! On 16.11.2013 22:05, Миша Тюрин wrote: > Hello! > > Could anyone review patch suggested by Jeff Janes ? > > Initial thread http://www.postgresql.org/message-id/flat/1384356585.995240612%40f50.i.mail.ru > > Thanks in advance! > >> >> On Wed, Nov 13, 2013 at 3:53 PM, Sergey Burladyan < eshkinkot@gmail.com > wrote: >>> Jeff Janes < jeff.janes@gmail.com > writes: >>> >>> If I not mistaken, looks like lazy_scan_heap() called from lazy_vacuum_rel() >>> (see [1]) skip pages, even if it run with scan_all == true, lazy_scan_heap() >>> does not increment scanned_pages if lazy_check_needs_freeze() return false, so >>> if this occurred at wraparound vacuum it cannot update pg_class, because >>> pg_class updated via this code: >>> >>> new_frozen_xid = FreezeLimit; >>> if (vacrelstats->scanned_pages < vacrelstats->rel_pages) >>> new_frozen_xid = InvalidTransactionId; >>> >>> vac_update_relstats(onerel, >>> new_rel_pages, >>> new_rel_tuples, >>> new_rel_allvisible, >>> vacrelstats->hasindex, >>> new_frozen_xid); >>> >>> so i think in our prevent wraparound vacuum vacrelstats->scanned_pages always >>> less than vacrelstats->rel_pages and pg_class relfrozenxid never updated. >> >> Yeah, I think that that is a bug. If the clean-up lock is unavailable but the page is inspected without it and foundnot to need freezing, then the page needs to be counted as scanned, but is not so counted. >> >> commit bbb6e559c4ea0fb4c346beda76736451dc24eb4e >> Date: Mon Nov 7 21:39:40 2011 -0500 >> >> But this was introduced in 9.2.0, so unless the OP didn't upgrade to 9.2 until recently, I don't know why it just startedhappening. >> >> It looks like a simple fix (to HEAD attached), but I don't know how to test it. >> >> Also, it seem like it might be worth issuing a warning if scan_all is true but all was not scanned. >> >> Cheers, >> >> Jeff >> >> -- >> Sent via pgsql-general mailing list (pgsql-general@postgresql.org) >> To make changes to your subscription: >> https://urldefense.proofpoint.com/v1/url?u=http://www.postgresql.org/mailpref/pgsql-general&k=oIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=xGch4oNJbpD%2BKPJECmgw4SLBhytSZLBX7UnkZhtNcpw%3D%0A&m=n4tu%2Fhw2DBAVCLO0UwZqdJsniWyqjnPt3OK%2FqepXInw%3D%0A&s=ffa1f6d45b713d12b320b72a4f417015498f57305664de0da209dc32f5e8a63b > >> > > -- > > > > -- - Heikki