Minor Description
In 10.3 I can do this:
ij> create table t0 (i int not null, v varchar(1) not null, constraint uq unique(v,i));
0 rows inserted/updated/deleted
ij> alter table t0 alter v set data type varchar(2);
0 rows inserted/updated/deleted
ij>
In 10.4 soft upgrade mode I cannot:
ij> create table t0 (i int not null, v varchar(1) not null, constraint uq unique(v,i));
0 rows inserted/updated/deleted
ij> alter table t0 alter v set data type varchar(2);
ERROR 42Z20: Column 'V' cannot be made nullable. It is part of a primary key or unique constraint, which cannot have any
nullable columns.
ij>