Re: Lifetime of commit timestamps

On Fri, Jun 22, 2018 at 05:21:32PM +0900, Kyotaro HORIGUCHI wrote:
> Hello.
> 
> I don't find any description in the documentation about the
> guaranteed lifetime of commit timestamps. I think they are
> preserved until corresponding xid goes beyond the freeze horizen,
> even though they are actually preserved longer for several
> reasons.
> 
> If it is not, I think such description is required in
> pg_xact_commit_timestamp().

> diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
> index 5dce8ef178..633e488cec 100644
> --- a/doc/src/sgml/func.sgml
> +++ b/doc/src/sgml/func.sgml
> @@ -18029,7 +18029,8 @@ SELECT collation for ('foo' COLLATE "de_DE");
>      These functions mainly provide information about when the transactions
>      were committed. They only provide useful data when
>      <xref linkend="guc-track-commit-timestamp"/> configuration option is enabled
> -    and only for transactions that were committed after it was enabled.
> +    and only for transactions that were committed after it was enabled. Commit
> +    timestamps for frozen tuples are removed at vacuum time.
>     </para>

Is this documentation change still relevant?

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

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