Re: BUG #18500: Detaching a partition with an index manually attached to the parent's index triggers Assert

Michael Paquier <michael@paquier.xyz> 于2024年6月12日周三 14:12写道：

> On Wed, Jun 12, 2024 at 01:49:32PM +0800, Tender Wang wrote:
> > Hi, all
> >
> > I found another crash case as below:
> > CREATE TABLE t (a integer) PARTITION BY RANGE (a);
> > CREATE TABLE tp (a integer PRIMARY KEY);
> > CREATE UNIQUE INDEX t_a_idx ON t (a);
> > ALTER TABLE t ATTACH PARTITION tp FOR VALUES FROM (0) TO (1000);
> > ALTER TABLE t DETACH PARTITION tp;
> >
> > If index of parent is not created by adding constraint, it will trigger
> > assert fail.
>
> The 4th command is I think incorrect to attach "t_a_idx" to "tp"'s
> primary key index because "t" does not have an equivalent entry in
> pg_constraint.  So that does not address the actual issue.
>
> > I look through the DetachPartitionFinalize(). The logic of detach indexes
> > finds a pg_inherits tuple,
> > then it goes to detach the constraint between parent and child. But in
> > AttachPartitionEnsureIndexes(),
> > it check whether constraint of parent is valid or not. If it is valid,
> then
> > the code will build constraint
> > connection between parent and child.
> >
> > I think we can do this check in DetachPartitionFinalize(). We skip to
> > detach the constraint if parent actually
> > does not have one. I try to fix theses issue in attached patch.
>
> Are you sure that this is correct?  This still makes "tp_pkey" a
> partition of "t_a_idx" while the parent table "t" has no constraint
> equivalent to "tp"'s primary key.  It seems to me that the correct
> answer in your command sequence is to *not* make "tp_pkey" a partition
> of the partitioned index "t_a_idx", and leave it alone.  Attaching
>

I think what you said above. I feel that we need that "tp_pkey" is a
partition
of the partitioned index "t_a_idx".  For example, below statement:

test=# alter table tp drop constraint tp_pkey;
ERROR:  cannot drop index tp_pkey because index t_a_idx requires it
HINT:  You can drop index t_a_idx instead.

If "tp_pkey" is not a partition of "t_a_idx", the primary key "tp_pkey" can
be dropped.

"tp_pkey" as a partition of "t_a_idx" is only OK as long as this index
> is used in a constraint equivalent to "tp_pkey".
>
> Having a PK on a partition while the parent does not have one is
> covered by a regression test in indexing.sql (see "Constraint-related
> indexes" and "primary key on child is okay").
> --
> Michael
>


-- 
Tender Wang
OpenPie:  https://en.openpie.com/