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From: jian he <[email protected]>
To: Andrew Dunstan <[email protected]>
To: Viktor Holmberg <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Subject: Re: support fast default for domain with constraints
Date: Thu, 12 Mar 2026 11:36:19 +0800
Message-ID: <CACJufxHomghtudwKpxqbVyy2n+cBPrahJjnpAo2OvRRXN-UE4w@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
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	<[email protected]>

On Thu, Mar 12, 2026 at 3:50 AM Andrew Dunstan <[email protected]> wrote:
> Also added some tests.

V11 looks good to me.


On Wed, Mar 11, 2026 at 6:34 PM Viktor Holmberg <[email protected]> wrote:
>
> I’ve been burned my this issue in the past so would be great if this could get in.
>
> + /*
> + * If the domain has volatile constraints, we must do a table rewrite
> + * since the constraint result could differ per row and cannot be
> + * evaluated once and cached as a missing value.
> + */
> + if (has_volatile)
> + {
> + Assert(has_domain_constraints);
> + tab->rewrite |= AT_REWRITE_DEFAULT_VAL;
> + }
>
> I'm not sure. But seems to me this makes the pre-existing guard for virtual columns
> redundant?
> I mean this code on line 7633:
> if (colDef->generated != ATTRIBUTE_GENERATED_VIRTUAL)
>  tab->rewrite |= AT_REWRITE_DEFAULT_VAL;
>

If the first `if (has_volatile)` is false, then
> if (colDef->generated != ATTRIBUTE_GENERATED_VIRTUAL)
>  tab->rewrite |= AT_REWRITE_DEFAULT_VAL;
is still reachable.

> Also, perhaps virtual generated columns could use a test?

Virtual generated columns based on domain are not currently supported.
I have a patch for it: https://commitfest.postgresql.org/patch/5725
but it's not doable now because of
https://git.postgresql.org/cgit/postgresql.git/commit/?id=0cd69b3d7ef357f2b43258de5831c4de0bd51dec
You may also be interested in https://commitfest.postgresql.org/patch/5907



--
jian
https://www.enterprisedb.com/





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