MongoDB implements the effect of querying a column in a relational database

Recently in Tornado\mongodb\ansible

There is a find () method in MongoDB that can send out all the tables in the collection, which I wrote at first.

Class Module_actionhandler (Tornado.web.RequestHandler):    def get (self, *args, **kwargs):        coll = Self.application.db.waitfish        hosts = Coll.find ({}, {' hostname ': 1, "_id": 0})        modulenames = [' ping ', ' setup ', ' Copy ']        self.render (            "module_action.html",            hosts = hosts,            modulenames = Modulenames,        )

Then in the template:

<select name= "hostname" >                {% for host in hosts%}                <option name= "{{host[' hostname ']}}" >{{host[' hos Tname ']}}</option>                {% End%}</select>

And then I thought about it. The find () method is to find all the tables, which is too hurtful.

So went to see the degree Niang, basically are listed a lot of query commands, a lot of methods.

In the end, I chose this one:

Class Module_actionhandler (Tornado.web.RequestHandler):    def get (self, *args, **kwargs):        coll = Self.application.db.waitfish        hosts = Coll.find ({}, {' hostname ': 1, "_id": 0}) #解释一下, here hostname:1 means return hostname column, because _ The ID column is returned every time so with 0 disabled, the template is also the same        modulenames = [' ping ', ' setup ', ' Copy ']        self.render (            "module_action.html",            hosts = hosts,            modulenames = Modulenames,        )

MongoDB implements the effect of querying a column in a relational database