Fix propagating attnotnull in multiple inheritance

In one of the many strange corner cases of multiple inheritance being
used, commit b0e96f3119 missed a CommandCounterIncrement() call after
updating the attnotnull flag during ALTER TABLE ADD COLUMN, which caused
a catalog tuple to be update attempted twice in the same command, giving
rise to a "tuple already updated by self" error.  Add the missing call
to solve that, and a test case that reproduces the scenario.

As a (perhaps surprising) secondary effect, this CCI addition triggers
another behavior change: when a primary key is added to a parent
partitioned table and the column in an existing partition does not have
a not-null constraint, we no longer error out.  This will probably be a
welcome change by some users, and I think it's unlikely that anybody
will miss the old behavior.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: http://postgr.es/m/045dec3f-9b3d-aa44-0c99-85f6992306c7@gmail.com

src/backend/commands/tablecmds.c

@@ -7757,6 +7757,10 @@ set_attnotnull(List **wqueue, Relation rel, AttrNumber attnum, bool recurse,
 		List	   *children;
 		ListCell   *lc;
 
+		/* Make above update visible, for multiple inheritance cases */
+		if (retval)
+			CommandCounterIncrement();
+
 		children = find_inheritance_children(RelationGetRelid(rel), lockmode);
 		foreach(lc, children)
 		{

src/test/regress/expected/constraints.out

@@ -1010,13 +1010,21 @@ ERROR:  constraint "cnn_parent_pkey" of relation "cnn_parent" does not exist
 create table cnn2_parted(a int primary key) partition by list (a);
 create table cnn2_part1(a int);
 alter table cnn2_parted attach partition cnn2_part1 for values in (1);
-ERROR:  primary key column "a" is not marked NOT NULL
+insert into cnn2_part1 values (null);
+ERROR:  null value in column "a" of relation "cnn2_part1" violates not-null constraint
+DETAIL:  Failing row contains (null).
 drop table cnn2_parted, cnn2_part1;
 create table cnn2_parted(a int not null) partition by list (a);
 create table cnn2_part1(a int primary key);
 alter table cnn2_parted attach partition cnn2_part1 for values in (1);
 ERROR:  column "a" in child table must be marked NOT NULL
 drop table cnn2_parted, cnn2_part1;
+create table cnn2_parted(a int) partition by list (a);
+create table cnn_part1 partition of cnn2_parted for values in (1, null);
+insert into cnn_part1 values (null);
+alter table cnn2_parted add primary key (a);
+ERROR:  column "a" of relation "cnn_part1" contains null values
+drop table cnn2_parted;
 -- columns in regular and LIKE inheritance should be marked not-nullable
 -- for primary keys, even if those are deferred
 CREATE TABLE notnull_tbl4 (a INTEGER PRIMARY KEY INITIALLY DEFERRED);

src/test/regress/expected/inherit.out

@@ -2177,6 +2177,14 @@ Child tables: cc1,
 
 alter table pp1 add primary key (f1);
 -- Leave these tables around, for pg_upgrade testing
+-- Test a not-null addition that must walk down the hierarchy
+CREATE TABLE inh_parent ();
+CREATE TABLE inh_child (i int) INHERITS (inh_parent);
+CREATE TABLE inh_grandchild () INHERITS (inh_parent, inh_child);
+ALTER TABLE inh_parent ADD COLUMN i int NOT NULL;
+NOTICE:  merging definition of column "i" for child "inh_child"
+NOTICE:  merging definition of column "i" for child "inh_grandchild"
+drop table inh_parent, inh_child, inh_grandchild;
 -- Test the same constraint name for different columns in different parents
 create table inh_parent1(a int constraint nn not null);
 create table inh_parent2(b int constraint nn not null);

src/test/regress/sql/constraints.sql

@@ -661,6 +661,7 @@ ALTER TABLE cnn_parent DROP CONSTRAINT cnn_parent_pkey;
 create table cnn2_parted(a int primary key) partition by list (a);
 create table cnn2_part1(a int);
 alter table cnn2_parted attach partition cnn2_part1 for values in (1);
+insert into cnn2_part1 values (null);
 drop table cnn2_parted, cnn2_part1;
 
 create table cnn2_parted(a int not null) partition by list (a);
@@ -668,6 +669,12 @@ create table cnn2_part1(a int primary key);
 alter table cnn2_parted attach partition cnn2_part1 for values in (1);
 drop table cnn2_parted, cnn2_part1;
 
+create table cnn2_parted(a int) partition by list (a);
+create table cnn_part1 partition of cnn2_parted for values in (1, null);
+insert into cnn_part1 values (null);
+alter table cnn2_parted add primary key (a);
+drop table cnn2_parted;
+
 -- columns in regular and LIKE inheritance should be marked not-nullable
 -- for primary keys, even if those are deferred
 CREATE TABLE notnull_tbl4 (a INTEGER PRIMARY KEY INITIALLY DEFERRED);

src/test/regress/sql/inherit.sql

@@ -804,6 +804,13 @@ alter table pp1 alter column f1 drop not null;
 alter table pp1 add primary key (f1);
 -- Leave these tables around, for pg_upgrade testing
 
+-- Test a not-null addition that must walk down the hierarchy
+CREATE TABLE inh_parent ();
+CREATE TABLE inh_child (i int) INHERITS (inh_parent);
+CREATE TABLE inh_grandchild () INHERITS (inh_parent, inh_child);
+ALTER TABLE inh_parent ADD COLUMN i int NOT NULL;
+drop table inh_parent, inh_child, inh_grandchild;
+
 -- Test the same constraint name for different columns in different parents
 create table inh_parent1(a int constraint nn not null);
 create table inh_parent2(b int constraint nn not null);