Re: Patch: show xid and xmin in pg_stat_activity and pg_stat_replication

On 2014-02-11 09:15:45 -0500, Robert Haas wrote:
> If I understand correctly, modifying PgBackendStatus adds additional
> fields to the shared memory data structure that are never used and
> will be returned by functions like pgstat_fetch_stat_beentry()
> unitialized.  That seems both inefficient and a pitfall for the
> unwary.

I don't think the will be unitialized, pgstat_fetch_stat_beentry() will
do a pgstat_read_current_status() if neccessary which will initialize
them.

But they do take up shared memory without really needing to. I
personally don't find that too bad, it's not much memory. If we want to
avoid it we could have a LocalPgBackendStatus that includes the normal
PgBackendStatus. Since pgstat_read_current_status() copies all the data
locally, that'd be a sensible point to fill it. While that will cause a
bit of churn, I'd guess we can use the infrastructure in the not too far
away future for other parts.

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
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