pg_last_xact_insert_timestamp

On Thu, Sep 8, 2011 at 7:06 AM, Chris Redekop <chris(at)replicon(dot)com> wrote:
> Is there anything available to get the last time a transaction
> occurred?....like say "pg_last_xact_timestamp"?  In order to accurately
> calculate how far behind my slave is I need to do something like
> master::pg_last_xact_timestamp() -
> slave::pg_last_xact_replay_timestamp()....currently I'm using now() instead
> of the pg_last_xact_timestamp() call, but then when the master is not busy
> the slave appears to lag behind.  I'm considering writing a C module to get
> the last modified file time of the xlog, but I'm hoping there is a better
> alternative that I haven't found yet....

The above has been posted in pgsql-general. The reason why Chris thinks
a counterpart of pg_last_xact_replay_timestamp() is required sounds
reasonable to me. So I'd like to propose new function
"pg_last_xact_insert_timestamp" as the counterpart, which returns the
timestamp of the last inserted commit or abort WAL record. I'll add the
attached patch into the next CF.

Comments?

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center