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From: Dominique Devienne <[email protected]>
To: Ron Johnson <[email protected]>
Cc: pgsql-generallists.postgresql.org <[email protected]>
Subject: Re: v18 virtual columns
Date: Thu, 20 Feb 2025 15:33:57 +0100
Message-ID: <CAFCRh--3iD9sSwakKvm9-Od+0RBEuLGy35dD72C5G9PzCYEiTg@mail.gmail.com> (raw)
In-Reply-To: <CANzqJaC0LCgK1RRKJ=qNTGxgkfFV-_F6keKmCxGBS6EWZ2jjKA@mail.gmail.com>
References: <CAFCRh-8grTkEy+73q79iXB+q+sD=Qkbz-vNAN1KJCF6PRLa=zg@mail.gmail.com>
	<CANzqJaC0LCgK1RRKJ=qNTGxgkfFV-_F6keKmCxGBS6EWZ2jjKA@mail.gmail.com>

On Thu, Feb 20, 2025 at 3:31 PM Ron Johnson <[email protected]> wrote:

> On Thu, Feb 20, 2025 at 8:07 AM Dominique Devienne <[email protected]>
> wrote:
>
>> Hi. I've just read
>> https://www.dbi-services.com/blog/postgresql-18-virtual-generated-columns/
>>
>> and I'm wondering whether there will be a way to ALTER existing STORED
>> generated columns, to be virtual? W/o rewriting the whole table that is.
>>
>
> What about dropping the existing stored column then adding the new virtual
> column?
>
> You won't get any disk space saving for existing records, but it's not
> going to rewrite the table.
>

Didn't think of that, but yes, I think that would work.
They are GENERATED columns, so the values stored are derived data anyway,
indeed.

I also didn't know DROP COLUMN was smart enough not rewriting the column,
that's good.

Thanks, --DD

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