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commit    bfec14d06de8d953260348b575f6645c1fb92f7f
Author:   Michael Paquier <michael@paquier.xyz>
Date:     Wed Jan 24 05:20:13 2024 +0000
First released in: 17.0, 12.18, 13.14, 14.11, 15.6, 16.2

    Fix ALTER TABLE .. ADD COLUMN with complex inheritance trees
    
    This command, when used to add a column on a parent table with a complex
    inheritance tree, tried to update multiple times the same tuple in
    pg_attribute for a child table when incrementing attinhcount, causing
    failures with "tuple already updated by self" because of a missing
    CommandCounterIncrement() between two updates.
    
    This exists for a rather long time, so backpatch all the way down.
    
    Reported-by: Alexander Lakhin
    Author: Tender Wang
    Reviewed-by: Richard Guo
    Discussion: https://postgr.es/m/18297-b04cd83a55b51e35@postgresql.org
    Backpatch-through: 12


 src/backend/commands/tablecmds.c      |  4 ++++
 src/test/regress/expected/inherit.out | 17 +++++++++++++++++
 src/test/regress/sql/inherit.sql      |  9 +++++++++
 3 files changed, 30 insertions(+)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 98fbe0588cc..ddc15c31c1f 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -6291,6 +6291,10 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel,
 							colDef->colname, RelationGetRelationName(rel))));
 
 			table_close(attrdesc, RowExclusiveLock);
+
+			/* Make the child column change visible */
+			CommandCounterIncrement();
+
 			return InvalidObjectAddress;
 		}
 	}
diff --git a/src/test/regress/expected/inherit.out b/src/test/regress/expected/inherit.out
index cb61d75b9ed..20973f96959 100644
--- a/src/test/regress/expected/inherit.out
+++ b/src/test/regress/expected/inherit.out
@@ -1063,6 +1063,23 @@ Inherits: inht1,
           inhs1
 
 DROP TABLE inhts;
+-- Test for adding a column to a parent table with complex inheritance
+CREATE TABLE inhta ();
+CREATE TABLE inhtb () INHERITS (inhta);
+CREATE TABLE inhtc () INHERITS (inhtb);
+CREATE TABLE inhtd () INHERITS (inhta, inhtb, inhtc);
+ALTER TABLE inhta ADD COLUMN i int;
+NOTICE:  merging definition of column "i" for child "inhtd"
+NOTICE:  merging definition of column "i" for child "inhtd"
+\d+ inhta
+                                   Table "public.inhta"
+ Column |  Type   | Collation | Nullable | Default | Storage | Stats target | Description 
+--------+---------+-----------+----------+---------+---------+--------------+-------------
+ i      | integer |           |          |         | plain   |              | 
+Child tables: inhtb,
+              inhtd
+
+DROP TABLE inhta, inhtb, inhtc, inhtd;
 -- Test for renaming in diamond inheritance
 CREATE TABLE inht2 (x int) INHERITS (inht1);
 CREATE TABLE inht3 (y int) INHERITS (inht1);
diff --git a/src/test/regress/sql/inherit.sql b/src/test/regress/sql/inherit.sql
index 1aa59e8355d..e9ae438b48a 100644
--- a/src/test/regress/sql/inherit.sql
+++ b/src/test/regress/sql/inherit.sql
@@ -353,6 +353,15 @@ ALTER TABLE inhts RENAME d TO dd;
 
 DROP TABLE inhts;
 
+-- Test for adding a column to a parent table with complex inheritance
+CREATE TABLE inhta ();
+CREATE TABLE inhtb () INHERITS (inhta);
+CREATE TABLE inhtc () INHERITS (inhtb);
+CREATE TABLE inhtd () INHERITS (inhta, inhtb, inhtc);
+ALTER TABLE inhta ADD COLUMN i int;
+\d+ inhta
+DROP TABLE inhta, inhtb, inhtc, inhtd;
+
 -- Test for renaming in diamond inheritance
 CREATE TABLE inht2 (x int) INHERITS (inht1);
 CREATE TABLE inht3 (y int) INHERITS (inht1);


[parent: dc9d424cf0cd]