Re: pg_dump misses comments on NOT NULL constraints

On Wed, Jun 18, 2025 at 8:13 AM Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
>
> I'm aware of a related open item [1] affecting both v17 and v18,
> but this seems like a separate issue, since it relates to a new v18 feature...
> Or we should treat them the same?
>
I think they are separate issues.

for check constraint that dump willed separately:
check constraint comments will go through dumpConstraint,
dumpTableConstraintComment
for check constraint that dump won't dump separately:
check constraint comments will go through dumpTableSchema,
dumpTableConstraintComment

Similarly we don't need to worry about not-null constraints that are
dumped separately.
dumpConstraint, dumpTableConstraintComment will do the job.

however per comment from collectComments say
"/* We needn't remember comments that don't match an */"

there is no ConstraintInfo for these inlined not-null, that means
``static CommentItem *comments = NULL;``
does not hold any comments for these inlined-null constraints.

so for
CREATE TABLE t (i int);
ALTER TABLE t ADD CONSTRAINT my_not_null NOT NULL i;
COMMENT ON CONSTRAINT my_not_null ON t IS 'my not null';

we can not locate the not-null constraint and use dumpComment to dump
the comments.
dumpComment->findComments will return nothing.
but we need to do the similar thing of dumpCommentExtended
``if (ncomments > 0){}`` code branch.

dumpTableSchema handles dumping of table column definitions, and tells us which
column print_notnull is true. Since we already know which columns have had
their not-null constraints printed, it makes sense to dump inline not-null
comments here too.

Please check the attached POC patch.