On 2014-02-14 23:03:43 -0500, Robert Haas wrote: > On Wed, Feb 12, 2014 at 8:00 AM, Christian Kruse > <christ...@2ndquadrant.com> wrote: > > On Wednesday 12 February 2014 11:14:56 Andres Freund wrote: > >> 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. > > > > That's a good idea. Attached you will find a patch implementing it > > that way; is this how you pictured it? > > > > Although I'm not sure if this shouldn't be done in two patches, one > > for the changes needed for LocalPgBackendStatus and one for the > > xid/xmin changes. > > Well, this version of the patch reveals a mighty interesting point: a > lot of the people who are calling pgstat_fetch_stat_beentry() don't > need this additional information and might prefer not to pay the cost > of fetching it. None of [functions] > actually need this new information; it's only ever used in one place. > So it seems like it might be wise to have pgstat_fetch_stat_beentry > continue to return the PgBackendStatus * and add a new function > pgstat_fetch_stat_local_beentry to fetch the LocalPgBackendStatus *; > then most of these call sites wouldn't need to change.
Hm maybe, seems to be as advantageous as not. Less lines changed, but a essentially duplicate function present. > It would still be the case that pgstat_read_current_status() pays the > price of fetching this information even if pg_stat_get_activity is > never called. But since that's probably by far the most commonly-used > API for this information, that's probably OK. Agreed. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
