db.getSiblingDB('admin').runCommand({setParameter: 1, failIndexKeyTooLong: false})

use DB

db.getCollectionNames().forEach(function(collection) { 
 indexes = db[collection].getIndexes();
 print("Indexes for " + collection + ":");
 printjson(indexes);
});

db.COLLECTION.dropIndexes()

db.getCollectionNames().forEach(function(collection) { 
  print("Indexes for " + collection + ":"); 
  db[collection].dropIndexes(); 
});

db.getCollectionNames().forEach(function(collName) { db.runCommand({dropIndexes: collName, index: "*"}); });

rake db:mongoid:create_indexes RAILS_ENV=production

db.COLLECTION.getIndexes()
db.getCollectionNames().forEach(function(collection){db[collection].reIndex()})