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help / color / mirror / Atom feedFrom: Tomas Vondra <[email protected]>
To: Tom Lane <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: sequences vs. synchronous replication
Date: Sat, 18 Dec 2021 22:48:11 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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On 12/18/21 22:27, Tom Lane wrote:
> Tomas Vondra <[email protected]> writes:
>> Here's a PoC demonstrating this idea. I'm not convinced it's the right
>> way to deal with this - it surely seems more like a duct tape fix than a
>> clean solution. But it does the trick.
>
> I was imagining something a whole lot simpler, like "don't try to
> cache unused sequence numbers when wal_level > minimal". We've
> accepted worse performance hits in that operating mode, and it'd
> fix a number of user complaints we've seen about weird sequence
> behavior on standbys.
>
What do you mean by "not caching unused sequence numbers"? Reducing
SEQ_LOG_VALS to 1, i.e. WAL-logging every sequence increment?
That'd work, but I wonder how significant the impact will be. It'd bet
it hurts the patch adding logical decoding of sequences quite a bit.
regards
--
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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