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Re: Avoiding rewrite in ALTER TABLE ALTER TYPE - Mailing list pgsql-hackers

From Robert Haas
Subject Re: Avoiding rewrite in ALTER TABLE ALTER TYPE
Date
Msg-id 721935F0-F996-4C11-850F-660BE77ED856@gmail.com
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In response to Re: Avoiding rewrite in ALTER TABLE ALTER TYPE  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Avoiding rewrite in ALTER TABLE ALTER TYPE
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On Dec 29, 2010, at 11:16 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I really really dislike the notion of a "verification scan": it's
> basically work that is going to be useless if it fails.

I think it has potential in cases like text to xml.  In that case it'll either work or fail, with no possibility of
requiringa do-over.  Scanning the whole table is a whole lot cheaper than rewriting it.  But I agree with your
assessmentof the "optimistic" verification scan case. 

...Robert

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