json - 如何将 PostgreSQL 触发器中的新数据存储为 JSON？

Question

我尝试按照以下说明去做:

https://wiki.postgresql.org/wiki/Audit_trigger

Auditing values as JSON

For PostgreSQL 9.2, or 9.1 with the fantastic json_91 addon, you can log the old and new values in the table as structured json instead of flat text, giving you much more power to query your audit history. Just change the types of v_old_data, v_new_data, original_data and new_data from TEXT to json, then replace ROW(OLD.) and ROW(NEW.) with row_to_json(OLD) and row_to_json(NEW) respectively.

但是这给我一个错误:

CREATE OR REPLACE FUNCTION add_log (name text, Action TEXT, data jsonb, OUT RETURNS BOOLEAN)
AS $$
BEGIN
    RETURNS = true;
END;
$$
LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION log_city() RETURNS TRIGGER AS 
$$
DECLARE
v_new_data jsonb;
BEGIN
    IF (TG_OP = 'UPDATE') THEN
        RETURN NEW;
    ELSIF (TG_OP = 'INSERT') THEN
        v_new_data := row_to_jsonb(NEW);
        EXECUTE add_log('City', 'City.New', v_new_data);
        RETURN NEW;
    END IF;
    RETURN NULL; -- result is ignored since this is an AFTER trigger
END;
$$ LANGUAGE plpgsql;

INSERT INTO Location (city, state, country) values ('a', 'b' , 'c')

它说:

ERROR: function row_to_jsonb(location) does not exist

如果我输入 v_new_data := row_to_jsonb(ROW(NEW)); 然后我得到:

ERROR: function row_to_jsonb(record) does not exist

Answer 1

它在 documentation 中说明那个

Table 9-42 shows the functions that are available for creating json and jsonb values. (There are no equivalent functions for jsonb, of the row_to_json and array_to_json functions. However, the to_jsonb function supplies much the same functionality as these functions would.)

因此必须使用 row_to_json。 row_to_jsonb 不存在，但 row_to_json 也会为 JSONB 类型生成所需的结果。