Re: Sequence's value can be rollback after a crashed recovery.

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От Andy Fan
Тема Re: Sequence's value can be rollback after a crashed recovery.
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Msg-id CAKU4AWoOstO3_7vfDDo73knFDj=qqZqH=+zLZXiWEt4QyNXQ6A@mail.gmail.com
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Ответ на Re: Sequence's value can be rollback after a crashed recovery.  (Tom Lane <tgl@sss.pgh.pa.us>)
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On Tue, Nov 23, 2021 at 4:31 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
"Bossart, Nathan" <bossartn@amazon.com> writes:
> I periodically hear rumblings about this behavior as well.  At the
> very least, it certainly ought to be documented if it isn't yet.  I
> wouldn't mind trying my hand at that.  Perhaps we could also add a new
> configuration parameter if users really want to take the performance
> hit.

A sequence's cache length is already configurable, no?


We can hit this issue even cache=1. And even if we added the XLogFlush,
with _cachesize=1_,  the Xlog is still recorded/flushed every 32 values. 

I know your opinion about this at [1], IIUC you probably miss the SEQ_LOG_VALS
design, it was designed for the  performance reason to avoid frequent xlog updates already. 
But after that,  the XLogSync is still not called which caused this issue. 


--
Best Regards
Andy Fan

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