PostgreSQL错误:关系已存在-创建表中存在外键

我正在做一张桌子如下:

CREATE TABLE creator.lists
(
    _id bigserial PRIMARY KEY NOT NULL,
    account_id bigint NOT NULL,
    created timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
    display_name text DEFAULT '',
    name text DEFAULT '',
    extra jsonb,

    FOREIGN KEY (account_id)
        REFERENCES creator.accounts (_id)
            ON DELETE CASCADE
);

但我得到了这个错误:

ERROR:  relation "account_id_index" already exists

当我跑步时:

CREATE INDEX
    account_id_index
ON
    creator.lists
(
    account_id
);

如何在外键上创建索引?我正在运行v11.1

只是一张纸条 ,我以前也为另一个表运行过类似的命令:

CREATE INDEX
    account_id_index
ON
    creator.contacts
    (
        account_id
    );

我不认为表之间的索引名必须是唯一的?