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From: Amit Langote <[email protected]>
To: Tom Lane <[email protected]>
Cc: Postgres General <[email protected]>
Subject: Re: Table Rewrite During ALTER TABLE ... ADD COLUMN ... DEFAULT NULL
Date: Thu, 3 Apr 2014 13:12:18 +0900
Message-ID: <CA+HiwqGzakcVbKbfxv6ThNcAmp_ZgakagKTM1u80PAF2mnNVcQ@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CA+HiwqE35_+z0_gFw9mp=_0MLgPfb=+QY910LG7C-sBNTvqdgg@mail.gmail.com>
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On Thu, Apr 3, 2014 at 12:54 PM, Tom Lane <[email protected]> wrote:
> Amit Langote <[email protected]> writes:
>> When I do the following:
>
>> ALTER TABLE table ADD COLUMN numeric(x) DEFAULT NULL;
>
>> The table is rewritten whereas notes section on the manual page for
>> ALTER TABLE says otherwise (which holds true for most of the cases
>> though).
>
> Try it without the explicit DEFAULT clause.
>

Thanks, that does the trick.

> Some experimentation suggests that we are smart about "DEFAULT NULL"
> unless the column type requires a length-coercion cast, in which
> case the default expression involves a function call, and that doesn't
> get elided.
>

Is there a warning about such behavior in the manual?
Is it useful to include it somewhere (not sure where though)?

--
Amit


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