Delete trigger and data integrity

Hello everyone,

I have this question regarding delete triggers and how it affects data integrity.

So here goes: I have this trigger which deletes everything before I insert new rows.

    CREATE OR REPLACE FUNCTION delete_records()

RETURNS TRIGGER AS $$

BEGIN

delete from "TABLE";

    RETURN NEW;

END;

$$

LANGUAGE plpgsql;

CREATE TRIGGER delete_on_insert

    BEFORE INSERT ON "TABLE"

    FOR EACH ROW EXECUTE PROCEDURE delete_records();

My question is what happens while this function is executed? Is there any chance the table can return empty data between the delete and insert commands? Or does a trigger like this block this possibility somehow?

Thank you