mongodb ensureIndex not working

> db.FileScan_files.ensureIndex({md5:1},{unique:true})
> db.FileScan_files.insert({md5:""})
> db.FileScan_files.insert({md5:""})


md5 is a bad name for mongodb
MongoDB speaks JavaScript, so utilize JS naming conventions.

> db.FileScan_files.ensureIndex({md:1},{unique:true})
> db.FileScan_files.insert({md:""})
> db.FileScan_files.insert({md:""})
E11000 duplicate key error index: filescan.FileScan_files.$md_1  dup key: { : "" }