composite versus sequence pk

Hi,

I'd like to present my concern and ask for your advice.

Here is the table:

Create table tTable (

A integer default nextval('"tTable_a_seq"'::text) not null,

B integer not null,

C integer not null,

D integer not null,

E double not null

);

Create sequence tTable_a_seq increment by 1 no maxvalue no minvalue
cache 1;

Initially the PK was created on A column. But really B, C, and D
combined are unique.

Do you know if there will be significant drop in performance on
INSERT/UPDATE operation if I will drop column A and create PK on B, C
and D?

I speculate that because there would be one less column to insert/update
it should not be worse. Not sure though what's the overhead of handling
composite PK on INSERT/UPDATE operation.

Regards

lk

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