Re: [PATCH 01/16] Overhaul walsender wakeup handling

Robert Haas <robertmhaas@gmail.com>

From: Robert Haas <robertmhaas@gmail.com>

To: Andres Freund <andres@2ndquadrant.com>

Cc: pgsql-hackers@postgresql.org

Date: 2012-06-22T14:59:45Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Don't waste the last segment of each 4GB logical log file.
- dfda6ebaec67 9.3.0 cited
Stamp HEAD as 9.3devel.
- bed88fceac04 9.3.0 cited
Wake WALSender to reduce data loss at failover for async commit.
- 2c8a4e9be273 9.2.0 cited
Make the visibility map crash-safe.
- 503c7305a1e3 9.2.0 cited

On Fri, Jun 22, 2012 at 10:45 AM, Andres Freund <andres@2ndquadrant.com> wrote:
>> > the likelihood of that as you know.
>> Hmm, well, I guess.  I'm still not sure I really understand what
>> benefit we're getting out of this.  If we lose a few WAL records for
>> an uncommitted transaction, who cares?  That transaction is gone
>> anyway.
> Well, before the simple fix Simon applied after my initial complaint you
> didn't get wakeups *at all* in the synchronous_commit=off case.
>
> Now, with the additional changes, the walsender is woken exactly when data is
> available to send and not always when a commit happens. I played around with
> various scenarios and it always was a win.

Can you elaborate on that a bit?  What scenarios did you play around
with, and what does "win" mean in this context?

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company