Horton

Re: ALTER TABLE lock strength reduction patch is unsafe

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Simon Riggs <simon@2ndquadrant.com>, Noah Misch <noah@leadboat.com>, Bruce Momjian <bruce@momjian.us>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2012-01-03T18:42:40Z
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. Add bytea_agg, parallel to string_agg.

  2. Fix ALTER TABLE ONLY .. DROP CONSTRAINT.

I wrote:
>> Another point that requires some thought is that switching SnapshotNow
>> to be MVCC-based will presumably result in a noticeable increase in each
>> backend's rate of wanting to acquire snapshots.

BTW, I wonder if this couldn't be ameliorated by establishing some
ground rules about how up-to-date a snapshot really needs to be.
Arguably, it should be okay for successive SnapshotNow scans to use the
same snapshot as long as we have not acquired a new lock in between.
If not, reusing an old snap doesn't introduce any race condition that
wasn't there already.

			regards, tom lane