Re: bug: repeated ALTER COLUMN SET DATA TYPE corrupt check constraint

hi.

while working on let ALTER COLUMN SET DATA TYPE cope with trigger dependency.
I found this bug, it involves several ALTER COLUMN SET DATA TYPE calls.

DROP TABLE IF EXISTS main_table;
CREATE TABLE main_table (a int, b int, check(a = b));
ALTER TABLE main_table ALTER COLUMN a SET DATA TYPE numeric;
ALTER TABLE main_table ALTER COLUMN a SET DATA TYPE int;
ALTER TABLE main_table ALTER COLUMN a SET DATA TYPE text;
ALTER TABLE main_table ALTER COLUMN b SET DATA TYPE text;
INSERT INTO main_table VALUES ('a', 'a');

This also applies to statistics, indexes. for statistics: the error is only
observable after running ANALYZE manually.