Re: why do we need two snapshots per query?

Robert Haas <robertmhaas@gmail.com>

From: Robert Haas <robertmhaas@gmail.com>

To: Florian Pflug <fgp@phlo.org>

Cc: Tom Lane <tgl@sss.pgh.pa.us>, Simon Riggs <simon@2ndquadrant.com>, Dimitri Fontaine <dimitri@2ndquadrant.fr>, pgsql-hackers <pgsql-hackers@postgresql.org>

Date: 2011-11-14T02:40:49Z

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 →

Fix copyright notices, other minor editing in new range-types code.
- f1585362856d 9.2.0 cited
Redesign the plancache mechanism for more flexibility and efficiency.
- e6faf910d750 9.2.0 cited

Attachments

just-one-snapshot-v2.patch (application/octet-stream) patch v2
refactor-portal-start.patch (application/octet-stream) patch

On Sun, Nov 13, 2011 at 8:57 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> In the -M extended case, we take a snapshot from exec_parse_message(),
> and the same two in the exec_bind_message() call that are taken in the
> -M prepared case.  So reducing the prepared case from two snapshots to
> one will reduce the extended case from three snapshots to two, thus
> saving one snapshot per query regardless of how it's executed.

And here are the revised patches.  Apply refactor-portal-start
(unchanged) first and then just-one-snapshot-v2.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company