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

From Robert Haas
Subject Re: ALTER TABLE lock strength reduction patch is unsafe
Date
Msg-id CA+TgmoaNehGhOTVc58bXLE0aL2efnNhDFS7-JyeVFhwPo3UQ8Q@mail.gmail.com
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In response to Re: ALTER TABLE lock strength reduction patch is unsafe  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: ALTER TABLE lock strength reduction patch is unsafe  ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>)
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On Tue, Jan 3, 2012 at 1:24 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Um ... you're supposing that only DDL uses SnapshotNow, which is wrong.
> I refer you to the parser, the planner, execution functions for arrays,
> records, enums, any sort of relcache reload, etc etc etc.  Yes, some
> of that is masked by backend-internal caching, some of the time, but
> it's folly to just assume that there are no SnapshotNow scans during
> normal queries.

Hmm.  That's unfortunate, because it seems difficult to construct a
test case that will exercise every feature in the system.

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

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