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Re: Altering a column type - Most efficient way - Mailing list pgsql-performance

From Ow Mun Heng
Subject Re: Altering a column type - Most efficient way
Date
Msg-id 1215742620.853.10.camel@neuromancer.home.net
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In response to Re: Altering a column type - Most efficient way  (Alvaro Herrera <alvherre@commandprompt.com>)
Responses Re: Altering a column type - Most efficient way  (Mario Weilguni <mweilguni@sime.com>)
Re: Altering a column type - Most efficient way  (Alvaro Herrera <alvherre@commandprompt.com>)
List pgsql-performance
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On Thu, 2008-07-10 at 09:57 -0400, Alvaro Herrera wrote:
> Ow Mun Heng wrote:
>
> > This is what I see on the table
> >
> > NEW attypmod = -1
> > OLD attypmod =  8
>
> 8 means varchar(4) which is what you said you had (4+4)
> -1 means unlimited size.
>

This is cool.

If it were this simple a change, I'm not certain why (I believe) PG is
checking each and every row to see if it will fit into the new column
definition/type.

Thus, I'm still a bit hesitant to do the change, although it is
definitely a very enticing thing to do. ( I presume also that this
change will be instantaneous and does not need to check on each and
every row of the table?)

Thanks./

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