Re: foreign key locks, 2nd attempt

Robert Haas <robertmhaas@gmail.com>

From: Robert Haas <robertmhaas@gmail.com>

To: Simon Riggs <simon@2ndquadrant.com>

Cc: Noah Misch <noah@leadboat.com>, Alvaro Herrera <alvherre@commandprompt.com>, Tom Lane <tgl@sss.pgh.pa.us>, Pg Hackers <pgsql-hackers@postgresql.org>

Date: 2012-03-16T00:37:36Z

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 →

Try to avoid running with a full fsync request queue.
- 7f242d880b5b 9.1.0 cited

On Thu, Mar 15, 2012 at 5:07 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> On Wed, Mar 14, 2012 at 5:23 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>>> You still have HEAP_XMAX_{INVALID,COMMITTED} to reduce the pressure on mxid
>>> lookups, so I think something more sophisticated is needed to exercise that
>>> cost.  Not sure what.
>>
>> I don't think HEAP_XMAX_COMMITTED is much help, because committed !=
>> all-visible.
>
> So because committed does not equal all visible there will be
> additional lookups on mxids? That's complete rubbish.

Noah seemed to be implying that once the updating transaction
committed, HEAP_XMAX_COMMITTED would get set and save the mxid lookup.
 But I think that's not true, because anyone who looks at the tuple
afterward will still need to know the exact xmax, to test it against
their snapshot.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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