Mongodb获取集合的字段以及数据类型信息

感觉很LOW的一个数据仓工具seatunel，竟然不能自动读取mongodb的表结构信息，需要手工创建。
然鹅，本人对mongodb也是新手，很多操作也不知所措，作为一个DBA，始终还是被研发的甩锅，没得办法只能想办法帮忙把集合的字段类型导出来给他。

网上找了很多方法都不行，坑太多了。

原本想使用mongodump工具导出，但是由于版本限制，mongodb4.4版本才支持schemaonly参数，本人服务器的版本是4.2

在此，为了方便需要的小伙伴，就此贴出无坑版操作代码，希望有所帮助：

winrs:PRIMARY> use testdb;
switched to db testdb
winrs:PRIMARY> var collection = db.dbaList;
winrs:PRIMARY> var fields = {};
winrs:PRIMARY> collection.find().forEach(function(doc) {
...     for (var key in doc) {
...         if (!fields[key]) {
...             fields[key] = typeof doc[key];
...         }
...     }
... });
winrs:PRIMARY> printjson(fields);
{"_id" : "number","n" : "string","brand" : "string","stand" : "string","group" : "string","area" : "string","dept" : "string","ip" : "string","port" : "number","sta" : "number","c_sta" : "number","e_flag" : "number","u_t" : "string","w_t" : "string","sta_t" : "string","c_sta_t" : "string","stop_t" : "string","power" : "number","v" : "number","s" : "number","h" : "number","b_a" : "number","w_a" : "number","h_a" : "number","l" : "number","e_c" : "object","m_c" : "object","o_c" : "object","timer" : "number","count" : "number","e_send" : "number","m_sta" : "number","s_sta" : "number","sta_his_id" : "string","alert_his_id" : "object","c_sta_his_id" : "string","alert_time" : "object","ensure" : "number","update_time" : "string","fmis_id" : "string","remarks" : "string","ensure_time" : "string","user_id" : "string"
}