message: More test to add/drop not_null
diff: @@ -71,3 +71,35 @@ SELECT * FROM t WHERE j IS NULL
  3 NULL
  5 NULL
  +# Insert null before&after drop constraint
  +statement ok
  +DROP TABLE IF EXISTS t
  +
  +statement ok
  +CREATE TABLE t(i INTEGER, j INTEGER)
  +
  +statement ok
  +INSERT INTO t SELECT 1,1 FROM RANGE(65536)
  +
  +# Set not null
  +statement ok
  +ALTER TABLE t ALTER COLUMN j SET NOT NULL
  +
  +# Failed to insert before drop constraint
  +statement error
  +INSERT INTO t VALUES (2, null)
  +
  +# Drop not null
  +statement ok
  +ALTER TABLE t ALTER COLUMN j DROP NOT NULL
  +
  +# Insert after drop constraint
  +statement ok
  +INSERT INTO t VALUES (3, null)
  +
  +# Only 1 null
  +query II
  +SELECT * FROM t WHERE j IS NULL
  +----
  +3 NULL
  +
  