Horton

Re: Hot Backup with rsync fails at pg_clog if under load

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Florian Pflug <fgp@phlo.org>, Aidan Van Dyk <aidan@highrise.ca>, Daniel Farina <daniel@heroku.com>, Chris Redekop <chris@replicon.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2011-10-27T11:36:37Z
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. Derive oldestActiveXid at correct time for Hot Standby.

  2. Start Hot Standby faster when initial snapshot is incomplete.

  3. Fix timing of Startup CLOG and MultiXact during Hot Standby

On Thu, Oct 27, 2011 at 5:37 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
> On Thu, Oct 27, 2011 at 4:36 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Robert Haas <robertmhaas@gmail.com> writes:
>>> On Wed, Oct 26, 2011 at 12:16 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
>>>> This fixes both the subtrans and clog bugs in one patch.
>>
>>> I don't see the point of changing StartupCLOG() to be an empty
>>> function and adding a new function TrimCLOG() that does everything
>>> StartupCLOG() used to do.
>>
>> +1 ... I found that overly cute also.
>
> It would have been even easier to move StartupCLOG() later, but then
> we'd need a big comment explaining why CLOG starts up at one point and
> subtrans starts up at another point, since that is very confusing way
> of doing things. I wrote it that way first and it definitely looks
> strange.
>
> It's much easier to understand that StartupCLOG() is actually a no-op
> and that we need to trim the clog at the end of recovery in all cases.

If it's a no-op, why have it at all?  I know we have a bunch of places
in the code where we have empty stubs where there used to be
initialization or cleanup code, but I've never found that particularly
good style.  If something no longer requires initialization in a
certain place, I think we should nuke the whole function.

-- 
Robert Haas
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