COPY speedup

Hi all.
In order to speed up the COPY ... FROM ... command, I've
disabled everything (primary key, not null, references, default and indexes)
in the table definition before doing the actual COPY.
Later I can restore them with ALTER TABLE ... and CREATE INDEX ...

My question is: is all this necessary, or could I save some of them (maybe
just the DEFAULT) with no speed cost?

Is there a way to "automate" this by using the information_schema?

Many thanks in advance.

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Reg me, please!