From: Tom Lane <tgl@sss.pgh.pa.us>
To: junhkang91@gmail.com
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18384: It's not bug just question about documentation
Date: Fri, 08 Mar 2024 10:28:26 -0500
Message-ID: <794154.1709911706@sss.pgh.pa.us> (raw)
In-Reply-To: <18384-d9f97269de73f0fa@postgresql.org>
References: <18384-d9f97269de73f0fa@postgresql.org>
PG Bug reporting form <noreply@postgresql.org> writes:
> "The internal transaction ID type xid is 32 bits wide and wraps around every
> 4 billion transactions."
> "it is necessary to vacuum every table in every database at least once every
> two billion transactions."
> why Postgresql needs to vacuum in every 2B transactions even though txid
> wraps on every 4 billion transactions (double time)?
Because an XID that's more than 2B transactions in the past will wrap
around and be seen as a bit less than 2B transactions in the future,
causing any rows bearing that XID to become invisible to current
transactions.
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, junhkang91@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18384: It's not bug just question about documentation
In-Reply-To: <794154.1709911706@sss.pgh.pa.us>
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