Re: cataloguing NOT NULL constraints

Hello Alvaro,

Please look at an anomaly introduced with b0e96f311.
The following script:
CREATE TABLE a ();
CREATE TABLE b (i int) INHERITS (a);
CREATE TABLE c () INHERITS (a, b);

ALTER TABLE a ADD COLUMN i int NOT NULL;

results in:
NOTICE:  merging definition of column "i" for child "b"
NOTICE:  merging definition of column "i" for child "c"
ERROR:  tuple already updated by self

(This is similar to bug #18297, but ATExecAddColumn() isn't guilty in this
case.)

Best regards,
Alexander