Re: not null constraints, again

On 2024-Sep-20, Tender Wang wrote:

> jian he <jian(dot)universality(at)gmail(dot)com> 于2024年9月20日周五 11:34写道：
>
> > another bug.
> > I will dig later, just want to share it first.
> >
> > minimum producer:
> > drop table if exists pp1,cc1, cc2,cc3;
> > create table pp1 (f1 int );
> > create table cc1 () inherits (pp1);
> > create table cc2() inherits(pp1,cc1);
> > create table cc3() inherits(pp1,cc1,cc2);
> >
> > alter table pp1 alter f1 set not null;
> > ERROR: tuple already updated by self
>
> I guess some place needs call CommandCounterIncrement().

Yeah ... this fixes it:

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 579b8075b5..3f66e43b9a 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -7877,12 +7877,6 @@ ATExecSetNotNull(List **wqueue, Relation rel, char *conName, char *colName,
{
List *children;

- /*
- * Make previous addition visible, in case we process the same
- * relation again while chasing down multiple inheritance trees.
- */
- CommandCounterIncrement();
-
children = find_inheritance_children(RelationGetRelid(rel),
lockmode);

@@ -7890,6 +7884,8 @@ ATExecSetNotNull(List **wqueue, Relation rel, char *conName, char *colName,
{
Relation childrel = table_open(childoid, NoLock);

+ CommandCounterIncrement();
+
ATExecSetNotNull(wqueue, childrel, conName, colName,
recurse, true, lockmode);
table_close(childrel, NoLock);

I was trying to save on the number of CCIs that we perform, but it's
likely not a wise expenditure of time given that this isn't a very
common scenario anyway. (Nobody with thousands of millions of children
tables will try to run thousands of commands in a single transaction
anyway ... so saving a few increments doesn't make any actual
difference. If such people exist, they can show us their use case and
we can investigate and fix it then.)

--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
"This is what I like so much about PostgreSQL. Most of the surprises
are of the "oh wow! That's cool" Not the "oh shit!" kind. :)"
Scott Marlowe, http://archives.postgresql.org/pgsql-admin/2008-10/msg00152.php