Horton

Re: [PATCH 10/16] Introduce the concept that wal has a 'origin' node

Andres Freund <andres@2ndquadrant.com>

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From: Andres Freund <andres@2ndquadrant.com>
To: Daniel Farina <daniel@heroku.com>
Cc: pgsql-hackers@postgresql.org, Simon Riggs <simon@2ndquadrant.com>
Date: 2012-06-18T21:53:53Z
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 →

  1. Don't waste the last segment of each 4GB logical log file.

  2. Stamp HEAD as 9.3devel.

  3. Wake WALSender to reduce data loss at failover for async commit.

  4. Make the visibility map crash-safe.

On Monday, June 18, 2012 11:51:27 PM Daniel Farina wrote:
> On Mon, Jun 18, 2012 at 8:50 AM, Andres Freund <andres@2ndquadrant.com> 
wrote:
> >> * Size of field. 16 bits is enough for 32,000 master nodes, which is
> >> quite a lot. Do we need that many? I think we may have need for a few
> >> flag bits, so I'd like to reserve at least 4 bits for flag bits, maybe
> >> 8 bits. Even if we don't need them in this release, I'd like to have
> >> them. If they remain unused after a few releases, we may choose to
> >> redeploy some of them as additional nodeids in future. I don't foresee
> >> complaints that 256 master nodes is too few anytime soon, so we can
> >> defer that decision.
> > 
> > I wished we had some flag bits available before as well. I find 256 nodes
> > a pretty low value to start with though, 4096 sounds better though, so I
> > would be happy with 4 flag bits. I think for cascading setups and such
> > you want to add node ids for every node, not only masters...
> > 
> > Any opinions from others on this?
> 
> What's the cost of going a lot higher?  Because if one makes enough
> numerical space available, one can assign node identities without a
> coordinator, a massive decrease in complexity.
It would increase the size of every wal record. We just have 16bit left there 
by chance...

Andres
-- 
 Andres Freund	                   http://www.2ndQuadrant.com/
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