PostgresQL 字符串隐式转换JSON脚本：
-- 隐式将varchar转换为json
CREATE OR REPLACE FUNCTION json_in_varchar(varchar) RETURNS json AS $$
SELECT json_in($1::cstring);
$$ LANGUAGE SQL IMMUTABLE;
DROP CAST IF EXISTS (varchar as json);
CREATE CAST (varchar AS json) WITH FUNCTION json_in_varchar(varchar) AS IMPLICIT;
-- 隐式将varchar转换为jsonb
CREATE OR REPLACE FUNCTION jsonb_in_varchar(varchar) RETURNS jsonb AS $$
SELECT jsonb_in($1::cstring);
$$ LANGUAGE SQL IMMUTABLE;
DROP CAST IF EXISTS (varchar as jsonb);
CREATE CAST (varchar AS jsonb) WITH FUNCTION jsonb_in_varchar(varchar) AS IMPLICIT;
我的数据库表中的字段类型为text，但是里面存储的是json格式的数据。需要通过上面的函数转换才能达到json效果。
select * from demo where jsonb_in_varchar(content_info)->>'json里面key属性' ='比较的值'