copy csv into partitioned table with unique index

Hi,
I configured a master table that is called "year_2018" :
create table year_2018(a int,b int c date);

The master table has a unique constraint on those 3 columns so that I wont
have any duplicated rows. Moreover, I configured a before insert trigger on
that table that creates a child table for each day in the year. The child
should include all the data related to that specific day.

Now, every day I got a csv file that I need to load to the year table. I
must load the data as fast as possible but I have 2 problems :
1)I must load the data as a bulk - via the copy command. However, the copy
command fails because sometimes I have duplicated rows.
2)I tried to use the pgloader extension but it fails because I have a
trigger before each insert.

-I cant load all the data into a temp table and then run insert into
year_2018 select * from temp because it takes too much time.

Any idea ?