raised checkpoint limit & manual checkpoint
От | Fabien COELHO |
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Тема | raised checkpoint limit & manual checkpoint |
Дата | |
Msg-id | alpine.DEB.2.20.1609240818210.6473@lancre обсуждение исходный текст |
Ответы |
Re: raised checkpoint limit & manual checkpoint
|
Список | pgsql-hackers |
Hello, The checkpoint time limit has just been raised to one day after a discussion started by Andres Freund: https://www.postgresql.org/message-id/20160202001320.GP8743%40awork2.anarazel.de I would have gone further up, say one week or even one month, but I think that this new limit is an improvement over the previous 1 hour maximum. Now ISTM that there is a possible use case which arises with this new setting and is not well addressed by postgresql: Let us say that an application has periods of high and low usage, say over a day, so that I want to avoid a checkpoint from 8 to 20, but I'm okay after that. I could raise the size and time limits so that they do not occur during these hours and plan to do a manual CHECKPOINT once a day when I see fit. Now the problem I see is that CHECKPOINT means "do a CHECKPOINT right now as fast as possible", i.e. there is no throttling whatsoever, which leads to heavy IO and may result in a very unresponsive database. I would suggest that a good complementary feature would be to allow a manual checkpoint to run over a period of time, say something like: CHECKPOINT OVER '10 hours'; That would target to complete after this period (whether it succeeds or not is another issue) instead of going as fast as possible, thus avoiding some performance degradation. Any thoughts? -- Fabien.
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