Fastest check if row exists in PostgreSQL

Question

I have a bunch of rows that I need to insert into table, but these inserts are always done in batches. So I want to check if a single row from the batch exists in the table

Answer 1

as @MikeM pointed out.

select exists(select 1 from contact where id=12)

with index on contact, it can usually reduce time cost to 1 ms.

CREATE INDEX index_contact on contact(id);