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help / color / mirror / Atom feedFrom: David G. Johnston <[email protected]>
To: Durgamahesh Manne <[email protected]>
Cc: [email protected] <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: Regarding vacuum freeze locking mechanism
Date: Wed, 17 Jul 2024 22:53:21 -0700
Message-ID: <CAKFQuwYZO8d0x=cnseo0RRZS7JAbC-=c2hkZ_mxetBheb6NELQ@mail.gmail.com> (raw)
In-Reply-To: <CAJCZko+DMHw2Cuqu09EKCW_1256GE4qfnhN-BV1X0Uoj0G2JFg@mail.gmail.com>
References: <CAJCZko+DMHw2Cuqu09EKCW_1256GE4qfnhN-BV1X0Uoj0G2JFg@mail.gmail.com>
On Wednesday, July 17, 2024, Durgamahesh Manne <[email protected]>
wrote:
> when autovacuum runs , it will freeze the transaction ID (TXID) of the
> table it's working on.
>
This statement is incorrect. A table as a whole does not have a txid.
Freezing makes it so individual tuples get assigned an always-in-the-past
txid. Then, the table can recompute how far away its furthest back txid is
from being considered in-the-future. That gap should increase since the
furthest away txids were the ones being frozen.
Inserts might get delayed a brief moment if it just happens the page they
want to insert onto is presently being worked on. But the odds there seem
low.
David J.
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To: [email protected]
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Subject: Re: Regarding vacuum freeze locking mechanism
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