mongoDb的索引

1 创建索引
 db.users.ensureIndex({"name":1})；
 db.users.dropIndex("name")
 db.users.dropIndexs()
 db.currentOp() 查看当前运行进程进度
2 explain()和hint()
hint("$natural":1)强制做全表扫描
3 唯一索引
db.users.ensureIndex({"name":1}，{"unique":true})；
 db.users.ensureIndex({"name":1},{"sparse":true}) sparse稀疏索引
db.users.ensureIndex({"name":1},{"unique":true,"dropDups":true}) dropDups去除重复数据
db.runCommand({getLastError:1})