| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | junhkang91(at)gmail(dot)com |
| Cc: | pgsql-bugs(at)lists(dot)postgresql(dot)org |
| Subject: | Re: BUG #18384: It's not bug just question about documentation |
| Date: | 2024-03-08 15:28:26 |
| Message-ID: | 794154.1709911706@sss.pgh.pa.us |
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| Lists: | pgsql-bugs |
PG Bug reporting form <noreply(at)postgresql(dot)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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