mongodb 从 mongo shell 操作所有数据库
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Operate on all databases from the mongo shell
提问by edebill
We have a system with many different mongo databases. I regularly want to write ad-hoc queries that will apply to all (or a subset) of them, without having a priori knowledge of what databases are there.
我们有一个包含许多不同 mongo 数据库的系统。我经常想编写适用于所有（或一个子集）的即席查询，而无需先验了解那里的数据库。
I can do show dbs, which will visually print a list, but is there a way to do something like:
我可以做show dbs，它会在视觉上打印一个列表，但是有没有办法做这样的事情：
var db_list = listDatabases();
for (i = 0; i < db_list.length; i++) {
do_something(db_list[i])
}
My problem with show dbsis that it doesn't capture any return values, so I can't do anything productive with the output.
我的问题show dbs是它没有捕获任何返回值，所以我不能对输出做任何有效率的事情。
回答by JohnnyHK
You can use the 'listDatabases'admin command for that:
您可以'listDatabases'为此使用admin 命令：
var db_list = db.adminCommand('listDatabases');
That returns an object that looks like this:
这将返回一个如下所示的对象：
{
"databases" : [
{
"name" : "test",
"sizeOnDisk" : 2097152000,
"empty" : false
},
{
"name" : "local",
"sizeOnDisk" : 1,
"empty" : true
}
],
"totalSize" : 8487174144,
"ok" : 1
}
回答by davey
There is also getDBNames() (i like how JohnnyHK's answer gets the size.
还有 getDBNames() （我喜欢 JohnnyHK 的答案如何获得大小。
d = db.getMongo().getDBNames()
[ "graylog2", "local", "admin", "test" ]
Then I can:
然后我可以：
for (var x in d) { db = new Mongo().getDB(d[x]); print(db); y = print(db.getCollectionNames()); }
