Horton

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

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@2ndquadrant.com>
Cc: Daniel Farina <daniel@heroku.com>, pgsql-hackers@postgresql.org, Simon Riggs <simon@2ndquadrant.com>
Date: 2012-06-19T06:03:04Z
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.

Andres Freund <andres@2ndquadrant.com> writes:
> On Monday, June 18, 2012 11:51:27 PM Daniel Farina wrote:
>> 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...

"Every WAL record"?  Why in heck would you attach it to every record?
Surely putting it in WAL page headers would be sufficient.  We could
easily afford to burn a page switch (if not a whole segment switch)
when changing masters.

I'm against the idea of eating any spare space we have in WAL record
headers for this purpose, anyway; there are likely to be more pressing
needs in future.

			regards, tom lane