Make sure the index is not working - MongoDB

Question

I am trying to provide an index in a document field, and its not at work. MongoDB version 2.0.2. It is very simple and somehow I feel that I might have missed something or not !!! It can insert 3 documents with the same blank line !!

Here are the details:

> use testinsert switched to db testinsert > db.users.ensureIndex({ name : 1}); > doc = { ... name : "" ... } { "name" : "" } > doc { "name" : "" } > db.users.stats(); { "ns" : "testinsert.users", "count" : 0, "size" : 0, "storageSize" : 8192, "numExtents" : 1, "nindexes" : 2, "lastExtentSize" : 8192, "paddingFactor" : 1, "flags" : 1, "totalIndexSize" : 16352, "indexSizes" : { "_id_" : 8176, "name_1" : 8176 }, "ok" : 1 } > db.users.insert(doc); > db.users.insert(doc); > db.users.insert(doc); > db.users.find(); { "_id" : ObjectId("4f1980dc7e154e6702c4914c"), "name" : "" } { "_id" : ObjectId("4f1980dd7e154e6702c4914d"), "name" : "" } { "_id" : ObjectId("4f1980dd7e154e6702c4914e"), "name" : "" } > db.users.ensureIndex({ name : 1}); > db.users.insert(doc); > db testinsert > db.users.find(); { "_id" : ObjectId("4f1980dc7e154e6702c4914c"), "name" : "" } { "_id" : ObjectId("4f1980dd7e154e6702c4914d"), "name" : "" } { "_id" : ObjectId("4f1980dd7e154e6702c4914e"), "name" : "" } { "_id" : ObjectId("4f1981557e154e6702c49150"), "name" : "" } > version(); version: 2.0.2 

can someone clarify what could be the problem!

Answer 1

There are no problems, you can see that the index is. Do you expect this to not duplicate items? To do this, you need to set a unique flag to true:

 db.users.ensureIndex({ name : 1},{unique: true}); 

UPDATE: starting again with {unique: true} does not work, you need to reset again and ensureIndex :

 db.users.dropIndex({name:1}) db.users.ensureIndex({ name : 1}, {unique:true, dropDups : true});