Pavel Stehule <pavel.steh...@gmail.com> writes:
> 2017-12-20 23:41 GMT+01:00 Tom Lane <t...@sss.pgh.pa.us>:
>> Hm, scratch that --- experimentation shows that the parser still produces
>> a CoerceToDomain node in that case, not a literal of the domain type.
> Why the rewrite doesn't reduce it? Or why parser does it?
Because ALTER DOMAIN can change what would be a valid value.
regression=# create domain myd as int;
CREATE DOMAIN
regression=# create view v1 as select 0::myd as c1;
CREATE VIEW
regression=# select * from v1;
c1
----
0
(1 row)
regression=# alter domain myd add check (value > 0);
ALTER DOMAIN
regression=# select * from v1;
ERROR: value for domain myd violates check constraint "myd_check"
If the view's expression had been reduced to just a Const when it
was stored, we'd not notice that the value is no longer valid for
the domain. So CoerceToDomain is always postponed till runtime.
regards, tom lane
