Re: support fast default for domain with constraints

On 2026-01-26 Mo 2:52 AM, jian he wrote:
> On Mon, Sep 1, 2025 at 2:27 PM jian he <jian(dot)universality(at)gmail(dot)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.
>
>
>

here's an updated patch set.

main changes:

. renamed DomainHaveVolatileConstraints renamed to
DomainHasVolatileConstraints, improved the comments and code structure

. squashed two commits into one, as there's only one user for the
soft-error functions

. rename  ExecPrepareExprExtended to ExecPrepareExprWithContext and
ExecInitExprExtended to ExecInitExprWithContext, with improved comments.

cheers

andrew

--
Andrew Dunstan
EDB: https://www.enterprisedb.com