Horton

Re: support fast default for domain with constraints

jian he <jian.universality@gmail.com>

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From: jian he <jian.universality@gmail.com>
To: PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2026-01-26T07:52:16Z
Lists: pgsql-hackers

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On Mon, Sep 1, 2025 at 2:27 PM jian he <jian.universality@gmail.com> wrote:
>
> summary of the attached v7.
> v7-0001, v7-00002: preparatory patch.
> v7-0003 adds fast default support for ALTER TABLE ADD COLUMN when the domain has
> non-volatile constraints.
> A table rewrite is still required for domains with volatile constraints.
>
> v7-0004 skip table rewrite (table scan only) for ALTER TABLE ADD
> COLUMN with domains has volatile constraints.
>

Hi.

rebase, and further simplified.

maybe we could perform a table scan for ALTER TABLE ADD COLUMN when the domain
has volatile constraints like v7-0004, avoiding a table rewrite.
However, this approach
feels inelegant, so I do not plan to pursue it.

So, the fast default now applies to domains with non-volatile constraint
expressions only.

Regarding the prior discussion about empty table behavior. This patch is
consistent with the master: not throwing an error if the default would fail the
domain constraints.



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

Commits

  1. Enable fast default for domains with non-volatile constraints

  2. Extend DomainHasConstraints() to optionally check constraint volatility

  3. Restrict virtual columns to use built-in functions and types

  4. Replace EEOP_DONE with special steps for return/no return

  5. Add soft error handling to some expression nodes