根据Mongo中的列值返回集合名称 [英] Return Collection names based on column value in Mongo

问题描述

我有5个集合C1，C2，C3，C4和N5，每个集合都有一个last_updated值.

I have 5 collections C1, C2, C3, C4 and N5 each having a last_updated value.

db.getCollectionNames().filter(function(c){ return c.indexOf('C')==0})

将返回所有以"C"开头的集合.

will return me all the collections that start with "C".

是否可以前进一步，并基于"last_updated"列进行过滤，以便我将获得昨天更新的所有"C"集合.

Is it possible to go one step ahead and do a filter based on "last_updated" column so that i will get all "C" collections that are updated yesterday.

类似的东西

 db.getCollectionNames().filter(function(c){ return (db.c.find({update_on: "01-Dec-2014"}).count()
 > 1)});

尽管查询运行良好，但没有产生任何结果.

Eventhough the query runs fine its not yeilding any result.

推荐答案

即使查询日期集合中存在一条记录，也需要返回true.

You need to return true even if one record is present is present in the collection for the queried date.

第二，db.c解析为值c，因此找到了一个不存在的名为c的集合的计数.要将c解析为变量，我们需要将其用作db[c].

Second, db.c is resolved to value c,Therefore finding the count of a collection named c, which does not exist. To resolve c as a variable, we need to use it as db[c].

下面修改的代码可以做到这一点:

The modified code below would do that:

db.getCollectionNames().filter(function(c){
 var rec = db[c].count({update_on: "01-Dec-2014"});
 return (rec > 0);
})

这篇关于根据Mongo中的列值返回集合名称的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！