btree index check, avoid create duplicate btree indexes, Avoid affecting performance

btree index check, avoid create duplicate btree indexes, Avoid affecting performance by the deplicate index.
for example:
add two index: db.collection.createIndex({a:1}) and db.collection.createIndex({a:11})
the tow index are actually the same, One of them is a useless index, but it can affect the insert performance.

In addition, They also affecting query performance because both are candidate indexes. This increases storage consts.