Re: BUG #18297: Error when adding a column to a parent table with complex inheritance

Hmm, thanks for the report.
I can repeat the aboved issue on master, even on pg10 and pg 11.
I analyzed this issue, and I found that ATExecAddColumn(), we forgot to
call CommandCounterIncrement() in if (colDef->inhcount > 0) {...} branch.
So the third(a->d) updates the first(a->b->c->d) tuple.
Attached patch is my quickly fixed solution.

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


PG Bug reporting form <noreply@postgresql.org> 于2024年1月16日周二 17:32写道：

> The following bug has been logged on the website:
>
> Bug reference:      18297
> Logged by:          Alexander Lakhin
> Email address:      exclusion@gmail.com
> PostgreSQL version: 16.1
> Operating system:   Ubuntu 22.04
> Description:
>
> The following query:
> CREATE TABLE a ();
> CREATE TABLE b () INHERITS (a);
> CREATE TABLE c () INHERITS (b);
> CREATE TABLE d () INHERITS (a,b,c);
>
> ALTER TABLE a ADD COLUMN i int;
> fails with:
> NOTICE:  merging definition of column "i" for child "d"
> ERROR:  tuple already updated by self
>
> While with a simpler hierarchy:
> CREATE TABLE a ();
> CREATE TABLE b () INHERITS (a);
> CREATE TABLE c () INHERITS (a,b);
>
> the column added successfully:
> ALTER TABLE a ADD COLUMN i int;
> NOTICE:  merging definition of column "i" for child "c"
> ALTER TABLE
>
> In the failed case the error occurred when table d was processed the third
> time. First (following chain a -> b -> c-> d) the table got the column i
> added, second (a -> b -> d) it got merged column definition, third
> (a -> d) an attempt to merge the column definition once more failed.
>
> This error can be seen at least on REL_12_STABLE .. master.
>
>