Can primary key be dropped and added back in?

I have a huge table to load (30+M rows).

Dropping indexes before loading will speed up my process, but I am not sure about the primary key that was created with the table creation. Is the Postgres primary key treated like an index? If yes, dropping the primary key might help my loading as well.... I can drop the primary key by

alter table tbleName drop constraint pkname_pkey.. it dropped clean this way.

But I haven't found the command to put the primary key back (all for testing now)

Is there a command to add the primary key back after loading the data?

Thanks

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