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Re: ALTER TABLE lock strength reduction patch is unsafe - Mailing list pgsql-hackers

From Noah Misch
Subject Re: ALTER TABLE lock strength reduction patch is unsafe
Date
Msg-id 20120102180626.GA23436@tornado.leadboat.com
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In response to Re: ALTER TABLE lock strength reduction patch is unsafe  (Simon Riggs <simon@2ndQuadrant.com>)
Responses Re: ALTER TABLE lock strength reduction patch is unsafe  (Simon Riggs <simon@2ndQuadrant.com>)
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On Mon, Jan 02, 2012 at 05:09:16PM +0000, Simon Riggs wrote:
> Attached patch makes SnapshotNow into an MVCC snapshot, initialised at
> the start of each scan iff SnapshotNow is passed as the scan's
> snapshot. It's fairly brief but seems to do the trick.

That's a neat trick.  However, if you start a new SnapshotNow scan while one is
ongoing, the primordial scan's snapshot will change mid-stream.

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