In case a column has a default value expression Is it possible for on conflict statement reset the column with the default expression without copy-paste the expression it self using default as a value while composing excluded record it self I.e. just to refer the default exactly from the update statement. Something like or even Answer Yes, you can use

Postgres on Conflict Update With Default Column Expression

In case a column has a default value expression

create table A (
...
b numeric default cos(54)
)

​x
 
create table A (...b numeric default cos(54))​

Is it possible for on conflict statement reset the column with the default expression without

I.e. just to refer the default exactly from the update statement. Something like

on conflict
update set b = default

 
on conflictupdate set b = default​

or even

on conflict
update set b = case when some_condition then default else A.b end

 
on conflictupdate set b = case when some_condition then default else A.b end​

Yes, you can use the DEFALT value in an upsert:

INSERT INTO t (foo,bar) VALUES (1,2)
ON CONFLICT (foo) DO UPDATE
SET bar = DEFAULT;

 
INSERT INTO t (foo,bar) VALUES (1,2)ON CONFLICT (foo) DO UPDATESET bar = DEFAULT;​