Re: Vacuum not cleaning up rows.
От | Tom Lane |
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Тема | Re: Vacuum not cleaning up rows. |
Дата | |
Msg-id | 29887.1561126102@sss.pgh.pa.us обсуждение исходный текст |
Ответ на | Re: Vacuum not cleaning up rows. (SBob <sbob@quadratum-braccas.com>) |
Ответы |
Re: Vacuum not cleaning up rows.
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Список | pgsql-admin |
SBob <sbob@quadratum-braccas.com> writes: > I do see older backend_start values (from around 6 hours ago). However I am confused as to how a connection to one databasein a cluster can prevenr vacuum from cleaning up row versions in a table within another database. How is that possiblesince onle one database has access to this table? Because the snapshot-horizon calculations are done system-wide. We can't just lobotomize them to only consider the current DB, because that would result in wrong row-cleanup decisions for shared catalogs. There are some attempts to refine that when vacuuming a non-shared table, but that can only go so far given the limited amount of state that backends expose about this. Doing better would require expending more effort in transaction start/transaction stop/snapshot creation, which are hot spots so it hasn't seemed like it'd be a good tradeoff. regards, tom lane
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