Horton

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

Kevin Grittner <kevin.grittner@wicourts.gov>

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From: "Kevin Grittner" <Kevin.Grittner@wicourts.gov>
To: "Simon Riggs" <simon@2ndquadrant.com>
Cc: "Andres Freund" <andres@2ndquadrant.com>, "Robert Haas" <robertmhaas@gmail.com>, "Daniel Farina" <daniel@heroku.com>,<pgsql-hackers@postgresql.org>, "Tom Lane" <tgl@sss.pgh.pa.us>
Date: 2012-06-19T22:15:03Z
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.

Simon Riggs <simon@2ndQuadrant.com> wrote:
 
> The proposal is to use WAL to generate the logical change stream.
> That has been shown in testing to be around x4 faster than having
> a separate change stream, which must also be WAL logged (as Jan
> noted).
 
Sure, that's why I want it.
 
> If we use WAL in this way, multi-master implies that the data will
> *always* be in a loop. So in any configuration we must be able to
> tell difference between changes made by one node and another.
 
Only if you assume that multi-master means identical databases all
replicating the same data to all the others.  If I have 72 master
replicating non-conflicting data to one consolidated database, I
consider that to be multi-master, too.  Especially if I have other
types of databases replicating disjoint data to the same
consolidated database, and the 72 sources have several databases
replicating disjoint sets of data to them.  We have about 1000
replications paths, none of which create a loop which can send data
back to the originator or cause conflicts.
 
Of course, none of these databases have the same OID for any given
object, and there are numerous different schemas among the
replicating databases, so I need to get to table and column names
before the data is of any use to me.
 
-Kevin