Re: [BUG] Fix DETACH with FK pointing to a partitioned table fails

On 2024-Jul-26, Junwang Zhao wrote:

> There is a bug report[0] Tender comments might be the same
> issue as this one, but I tried Alvaro's and mine patch, neither
> could solve that problem, I did not tried Tender's earlier patch
> thought. I post the test script below in case you are interested.

Yeah, I've been looking at this whole debacle this week and after
looking at it more closely, I realized that the overall problem requires
a much more invasive solution -- namely, that on DETACH, if the
referenced table is partitioned, we need to create additional
pg_constraint entries from the now-standalone table (was partition) to
each of the partitions of the referenced table; and also add action
triggers to each of those.  Without that, the constraint is incomplete
and doesn't work (as reported multiple times already).

One thing I have not yet tried is what if the partition being detach is
also partitioned.  I mean, do we need to handle each sub-partition
explicitly in some way?  I think the answer is no, but it needs tests.

I have written the patch to do this on detach, and AFAICS it works well,
though it changes the behavior of some existing tests (IIRC related to
self-referencing FKs).  Also, the next problem is making sure that
ATTACH deals with it correctly.  I'm on this bit today.

Self-referencing FKs seem to have additional problems :-(

The queries I was talking about are these

\set tables ''''prim.*''',''forign.*''',''''lone''''

select oid, conparentid, contype, conname, conrelid::regclass, confrelid::regclass, conkey, confkey, conindid::regclass
frompg_constraint where contype = 'f' and (conrelid::regclass::text ~ any (array[:tables]) or confrelid::regclass::text
~any (array[:tables])) order by contype, conrelid, confrelid; select tgconstraint, oid, tgrelid::regclass,
tgconstrrelid::regclass,tgname, tgparentid, tgconstrindid::regclass, tgfoid::regproc from pg_trigger where tgconstraint
in(select oid from pg_constraint where conrelid::regclass::text ~ any (array[:tables]) or confrelid::regclass::text ~
any(array[:tables])) order by tgconstraint, tgrelid::regclass::text, tgfoid;
 

Written as a single line in psql they let you quickly see all the
constraints and their associated triggers, so for instance you can see
whether this sequence

create table prim (a int primary key) partition by list (a);
create table prim1 partition of prim for values in (1);
create table prim2 partition of prim for values in (2);
create table forign (a int references prim) partition by list (a);
create table forign1 partition of forign for values in (1);
create table forign2 partition of forign for values in (2);
alter table forign detach partition forign1;

produces the same set of constraints and triggers as this other sequence

create table prim (a int primary key) partition by list (a);
create table prim1 partition of prim for values in (1);
create table prim2 partition of prim for values in (2);
create table forign (a int references prim) partition by list (a);
create table forign2 partition of forign for values in (2);
create table forign1 (a int references prim);


The patch is more or less like the attached, far from ready.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
Syntax error: function hell() needs an argument.
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