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help / color / mirror / Atom feedFrom: Tom Lane <[email protected]>
To: Andreas Karlsson <[email protected]>
Cc: Babak Ghadiri <[email protected]>
Cc: [email protected]
Subject: Re: Parallelizing startup with many databases
Date: Fri, 02 Jan 2026 19:02:27 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CAEkHFKSxYO7Ryv_UNNGSe88zosg0_Q_dop6hXN0oCoYK28EZtA@mail.gmail.com>
<[email protected]>
Andreas Karlsson <[email protected]> writes:
> On 1/2/26 8:55 AM, Babak Ghadiri wrote:
>> In PostgreSQL 16, startup appears to initialize databases sequentially and
>> primarily uses a single CPU core. In clusters with a very large number of
>> databases (around 5,000 in our case), this results in noticeably long
>> startup times after restarts or crash recovery.
> Have you measured what is actually causing the slow startup? Without
> knowing what is actually slow it is hard to say if threading would even
> help.
"perf" results would likely be useful.
I tried creating 5000 databases here and didn't notice any particular
increase in server startup time (didn't try crash-recovery case).
So whatever this is is likely somewhat configuration- or
platform-dependent.
Having said that, 5000 databases sounds like an anti-pattern to
begin with. You're paying for an additional copy of the system
catalogs for each one.
regards, tom lane
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