CREATE TABLE IF NOT EXISTS "contacts" (    "id" SERIAL PRIMARY KEY,    "user_id_a" INTEGER REFERENCES users (id) NOT NULL,    "user_id_b" INTEGER REFERENCES users (id) NOT NULL,    "a_to_b" BOOLEAN NOT NULL,    "should_notify" BOOLEAN NOT NULL,    "accepted" BOOLEAN NOT NULL); CREATE UNIQUE INDEX "index_contacts_user_ids" ON "contacts" ("user_id_a", "user_id_b");CREATE INDEX "index_contacts_user_id_b" ON "contacts" ("user_id_b");